Full NAO bibliography
The list below contains all articles and proceedings which refer to
the "North Atlantic Oscillation" in either the title or the abstract
published over the period 1981-99. The references are listed in order
of most recent to oldest.
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search for any keywords of interest.
(1) TI: Variation of the NAO and NPO associated with climate jump in
the 1960s
AU: Li,CY, Li,GL
NA: CHINESE ACAD SCI,INST ATMOSPHER PHYS,LASG,BEIJING
100080,PEOPLES R CHINA
JN: CHINESE SCIENCE BULLETIN, 1999, Vol.44, No.21, pp.1983-1987
IS: 1001-6538
DT: Article
AB: The interannual variation of the North Atlantic Oscillation
(NAO) and North Pacific Oscillation (NPO) and its relationship
with the climate jump in the Northern Hemisphere in the 1960s,
are discussed using the data analyses. It is clearly shown that
the amplitudes of the NAO and NPO were all increased obviously
in the 1960s and the main period of the oscillations changed
from 3-4 years before the 1960s to 8-15 years after the 1960s.
Therefore, the climate jump in the 1960s is closely related to
the anomalies of the NAO and NPO.
KP: NORTH-ATLANTIC OSCILLATION, HEMISPHERE
WA: North Atlantic Oscillation (NAO), North Pacific Oscillation
(NPO), climate jump
(2) TI: An intercomparison between low-frequency variability indices
AU: Cerlini,PB, Corti,S, Tibaldi,S
NA: UNIV BOLOGNA,DEPT EARTH & GEOENVIRONM SCI,VIA ZAMBONI
67,BOLOGNA,ITALY
INTERUNIV COMP CTR,CINECA,BOLOGNA,ITALY
UNIV BOLOGNA,DEPT PHYS,SMR,REG METEOROL SERV ARPA EMILIA
ROMAGNA,BOLOGNA,ITALY
UNIV BOLOGNA,DEPT PHYS,ATMOSPHER DYNAM GRP,BOLOGNA,ITALY
JN: TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY, 1999,
Vol.51, No.5, pp.773-789
IS: 0280-6495
DT: Article
AB: Possible connections between spatial patterns, of limited
regional extent and identified in teleconnection patterns and
in blocking climatology studies, with hemispheric planetary-
wave activity modes defined by the wave amplitude index (WAI)
are investigated. The WAI probability density function (PDF)
for the northern extratropics winter fields is estimated and
the sensitivity of the WAI distribution to the presence of low-
frequency variability modes is evaluated by stratifying the
available dataset according to the sign of blocking and
teleconnection indices. It is found that low-frequency
variability modes affect both the mean and the variance of the
wave amplitude index. Both the positive phase of the North
Atlantic Oscillation (NAO) and the negative phase of the
Pacific North American pattern (PNA) are associated with an
enhanced frequency of very large amplitude planetary waves.
Furthermore, distributions characterised by a maximum
corresponding to high WAI values also exhibit a large variance.
Negative NAO and positive PNA influence the mean and the
variance of WAI PDF in the opposite sense. Similar results are
found when the blocking index is considered. WAI PDFs relative
to highly blocked months are broader with a secondary maximum
corresponding to very high WAI values.
KP: PROBABILITY DENSITY DISTRIBUTION, ATMOSPHERIC WAVE AMPLITUDE,
NORTHERN-HEMISPHERE WINTER, QUASI-GEOSTROPHIC MODEL, WEATHER
REGIMES, FLOW REGIMES, OBSERVATIONAL EVIDENCE, PERSISTENT
ANOMALIES, BLOCKING, CIRCULATION
(3) TI: Dependence of the upper middle atmosphere on tropospheric
circulation: Correlation of European winter rainfall and
midlatitude mesopause region zonal winds
AU: Jacobi,C, Kurschner,D
NA: UNIV LEIPZIG,INST METEOROL,STEPHANSTR 3,D-04103 LEIPZIG,GERMANY
UNIV LEIPZIG,INST GEOPHYS & GEOL,COLLM OBSERV,D-04779
WERMSDORF,GERMANY
JN: METEOROLOGISCHE ZEITSCHRIFT, 1999, Vol.8, No.4, pp.132-138
IS: 0941-2948
DT: Article
AB: The winter midlatitude upper mesosphere/lower thermosphere
zonal winds are connected with the northern hemisphere
troposphere circulation, such that mesopause region zonal
westerly winds are stronger when North Atlantic westerly winds
onto Europe are stronger. Since European rainfall rates are
connected with the North Atlantic tropospheric circulation,
e.g. expressed through a connection with the North Atlantic
Oscillation, this leads to a connection between European
rainfall and mesopause region circulation, too. Winter rainfall
over Northern Europe is larger, when the upper atmosphere zonal
prevailing wind is stronger, while in the mediterranean an
opposite correlation is found. However, this connection does
not give a hint of a direct coupling between upper
mesosphere/lower thermosphere winds and European rainfall, but
rather shows that both European tropospheric and upper
atmosphere dynamical parameters are both included into large-
scale circulation patterns.
KP: NORTH-ATLANTIC OSCILLATION, LONG-TERM TRENDS, STRATOSPHERIC
CIRCULATION, GAUGE OBSERVATIONS, PRECIPITATION, PATTERNS, FIELD
(4) TI: Changes of the plankton spring outburst related to the North
Atlantic Oscillation
AU: Weyhenmeyer,GA, Blenckner,T, Pettersson,K
NA: UPPSALA UNIV,DEPT LIMNOL,ERKEN LAB,EVOLUTIONARY BIOL CTR,NORR
MALMA 4200,S-76173 NORRTALJE,SWEDEN
JN: LIMNOLOGY AND OCEANOGRAPHY, 1999, Vol.44, No.7, pp.1788-1792
IS: 0024-3590
DT: Article
AB: Changes in the timing, composition, and intensity of freshwater
phytoplankton blooms are known to have an impact on water
quality and aquatic ecosystem functions. Factors provoking
these changes are, therefore, of major importance. In Lake
Erken in southeastern Sweden considerable changes in the timing
and large variations in the composition of phytoplankton spring
peaks have been observed during the past 45 yr. Here we show
that long-term changes and variations in Lake Erken are
strongly related to a single global parameter-the North
Atlantic Oscillation (NAO). Even regional parameters that are
known to have most influence on the spring development of
phytoplankton such as ice break-up and nutrient concentrations
could not provide a more conclusive explanation of the observed
changes in spring phytoplankton, making the NAO a very powerful
and simple tool in determining the timing and composition of
phytoplankton spring peaks in a temperate lake.
KP: LAKE-ERKEN, PHYTOPLANKTON, VARIABILITY, TEMPERATURES, CLIMATE,
ENGLAND, ECOLOGY, SWEDEN
(5) TI: Spatial patterns of variability in the global surface air
temperature data set
AU: Kelly,PM, Jones,PD, Jia,PQ
NA: UNIV E ANGLIA,SCH ENVIRONM SCI,CLIMAT RES UNIT,NORWICH NR4
7TJ,NORFOLK,ENGLAND
CHINESE ACAD METEOROL SCI,POLAR METEOROL RES LAB,BEIJING
100081,PEOPLES R CHINA
JN: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1999, Vol.104,
No.D20, pp.24237-24256
IS: 0747-7309
DT: Article
AB: We identify the major spatial patterns of variability in the
global surface air temperature data set using empirical
orthogonal analysis. We rotate the major components to simplify
physical interpretation. Of the five patterns which account for
the largest proportion of the total variance in the data set,
three are global in extent and two are continental in scale.
The pattern accounting for most of the variance in the data set
indicates a global change in temperature, affecting most
regions in the same sense but most marked in lower latitudes.
The second most important pattern is a measure of the El Nino-
Southern Oscillation phenomenon. The third pattern represents a
contrast in temperature between the northern and southern
oceans and is shown to be related to Sahel rainfall variations,
confirming, though with reservations, the results of previous
work, The fourth pattern is an index of the temperature effects
of the North Atlantic Oscillation. The fifth pattern is a
measure of temperature variations over Siberia, It is shown
that this component is related to an atmospheric circulation
fluctuation affecting, among other things, the strength of the
depression track over the Barents and Kara Seas and neighboring
areas. We term this process the Euro-Siberian Oscillation, The
effects of changing data coverage are explored, and it is shown
that patterns with a strong maritime component are particularly
susceptible to this form of inhomogeneity, Finally, potential
causal mechanisms, such as volcanic pollution of the
atmosphere, are investigated, and the evolution over time of
the spatial response to these forcing factors is defined using
the empirical orthogonal functions. The analysis demonstrates
that empirical orthogonal functions representing the spatial
patterns of temperature change provide a concise means of
monitoring climate trends and can assist identification of the
causes of recent climate change as well as supporting climate
model validation and assessment of the representativeness and
reliability of climate reconstructions based on proxy
indicators such as tree ring data.
KP: NORTH-ATLANTIC OSCILLATION, NINO SOUTHERN OSCILLATION, LATITUDE
VOLCANIC-ERUPTIONS, EL-NINO, STRATOSPHERIC AEROSOLS, CLIMATE
VARIABILITY, RAINFALL, TRENDS, PRECIPITATION, ASSOCIATION
(6) TI: Climate changes detected through the world's longest sea level
series
AU: Ekman,M
NA: NATL LAND SURVEY,GEODET RES DIV,GAVLE,SWEDEN
SUMMER INST HIST GEOPHYS,BOMARSUND,ALAND ISLANDS,FINLAND
JN: GLOBAL AND PLANETARY CHANGE, 1999, Vol.21, No.4, pp.215-224
IS: 0921-8181
DT: Article
AB: The sea level series of Stockholm in the Baltic Sea, commencing
already in 1774, is analysed in various ways together with
contemporary climate data, in order to investigate long-term
sea level changes and their relations to climate changes.
First, a study of the eustatic rise of sea level, based on
annual mean sea levels, is performed, and compared with other
sea level and climate studies. It is concluded that the general
climatic rise of sea level has increased significantly (99.9%)
from about 0.0 mm/year during the end of the Little Ice Age, to
about 1.0 mm/year during the past century, characterized by
melting of glaciers. Such sea level changes due to northern
hemisphere climate variations since 800 A.D. have (hitherto)
probably always kept within -1.5 and +1.5 mm/year, with an
average fairly close to zero.
Second, an investigation of the sea level variability, also
based on annual mean sea levels, is performed together with
temperature and wind variabilities. It is found that the
interannual sea level variability of the Baltic Sea has
decreased significantly (98%) from the end of the 1700s to the
beginning of the 1900s; after that it has increased
significantly (95%) again. Precisely the same is found to apply
to winter climate or, more specifically, to the interannual
winter temperature variability and the interannual winter wind
variability. The common origin of all these long-term changes
turn out to be two consecutive winter wind processes over the
North and Baltic Seas, especially the Baltic entrance. From the
end of the 1700s to the beginning of the 1900s, there has been
a rapidly decreasing number of dominating winter winds from
northeast, and after that there has been an increasing number
of dominating winter winds from southwest. This may indicate
corresponding long-term changes in the North Atlantic
Oscillation.
Third, using monthly mean sea levels together with
corresponding wind data, seasonal variations are investigated.
The seasonal sea level variation in the Baltic Sea has
increased significantly (99%) since the early 1800s, together
with a shift of the maximum from late summer to early winter.
It is found that the main origin is a secular change of the
winter wind conditions over the Baltic entrance, with
increasing southwesterly winds in early winter. This might also
be related to a long-term change in the North Atlantic
Oscillation. (C) 1999 Elsevier Science B.V. All rights
reserved.
KP: BALTIC-SEA, POLE TIDE, NORTH-SEA, RECORDS, MODELS
WA: climate changes, sea level changes, Baltic Sea
(7) TI: Mixing and convection in the Greenland Sea from a tracer-
release experiment
AU: Watson,AJ, Messias,MJ, Fogelqvist,E, VanScoy,KA, Johannessen,T,
Oliver,KIC, Stevens,DP, Rey,F, Tanhua,T, Olsson,KA, Carse,F,
Simonsen,K, Ledwell,JR, Jansen,E, Cooper,DJ, Kruepke,JA,
Guilyardi,E
NA: UNIV E ANGLIA,SCH ENVIRONM SCI,NORWICH NR4 7TJ,NORFOLK,ENGLAND
CHALMERS UNIV TECHNOL,DEPT ANALYT & MARINE CHEM,S-41296
GOTHENBURG,SWEDEN
UNIV WISCONSIN,MADISON,WI,53706
UNIV BERGEN,DEPT GEOL,N-5007 BERGEN,NORWAY
UNIV E ANGLIA,SCH MATH,NORWICH NR4 7TJ,NORFOLK,ENGLAND
INST MARINE RES,DEPT MARINE ENVIRONM,N-5024 BERGEN,NORWAY
UNIV FAROE ISL,FO-100 TORSHAVN,FAROE ISLANDS,DENMARK
WOODS HOLE OCEANOG INST,WOODS HOLE,MA,02543
JN: NATURE, 1999, Vol.401, No.6756, pp.902-904
IS: 0028-0836
DT: Article
AB: Convective vertical mixing in restricted areas of the subpolar
oceans, such as the Greenland Sea, is thought to be the process
responsible for forming much of the dense water of the ocean
interior(1,2). Deep-water formation varies substantially on
annual and decadal timescales(3-5), and responds to regional
climate signals such as the North Atlantic Oscillation(6,7);
its variations may therefore give early warning of changes in
the thermohaline circulation that may accompany climate
changes. Here we report direct measurements of vertical mixing,
by convection and by turbulence, from a sulphur hexafluoride
tracer-release experiment in the central Greenland Sea gyre. In
summer, we found rapid turbulent vertical mixing of about 1.1
cm(2) s-(1). In the following late winter, part of the water
column was mixed more vigorously by convection, indicated by
the rising and vertical redistribution of the tracer patch in
the centre of the gyre. At the same time, mixing outside the
gyre centre was only slightly greater than in summer. The
results suggest that about 10% of the water in the gyre centre
was vertically transported in convective plumes, which reached
from the surface to, at their deepest, 1,200-1,400 m.
Convection was limited to a very restricted area, however, and
smaller volumes of water were transported to depth than
previously estimated(9). Our results imply that it may be the
rapid year-round turbulent mixing, rather than convection, that
dominates vertical mixing in the region as a whole.
KP: DEEP CONVECTION, ARCTIC-OCEAN, CIRCULATION, PYCNOCLINE, WATERS
(8) TI: Ecosystem consequences of wolf behavioural response to climate
AU: Post,E, Peterson,RO, Stenseth,NC, McLaren,BE
NA: UNIV OSLO,DEPT BIOL,DIV ZOOL,POB 1050,N-0316 OSLO,NORWAY
MICHIGAN TECHNOL UNIV,SCH FORESTRY & WOOD
PROD,HOUGHTON,MI,49931
DEPT FOREST RESOURCES,WILDLIFE DIV,ST JOHNS,NF A1B 4J6,CANADA
JN: NATURE, 1999, Vol.401, No.6756, pp.905-907
IS: 0028-0836
DT: Article
AB: Because apex predators exert considerable influence on the
structure and function of top-down ecosystems(1-3), their
responses to climate may shape responses at lower trophic
levels(4). Previous reports of trophic cascades and ecosystem
dynamics induced by predators have focused on changes in their
abundance(5-8), whereas we investigated whether changes in
predator behaviour could precipitate cascades of similar
ecological scale. Here we report the ecological consequences of
predator behavioural response to global climatic variation
using 40 years of data on wolf predation from Isle Royale, USA,
where wolves limit abundance of moose(9), which limit
productivity of fir trees(10). In response to increases in
winter snow related to the North Atlantic Oscillation, wolves
hunted in larger packs and, consequently, tripled the number of
moose killed per day compared with less snowy years when they
hunted in smaller packs. Following increased predation rates,
moose abundance declined, and, following release from heavy
browsing, growth of understory fir increased. Hence, cascading
behavioural responses of apex predators may be a substantial
link in the pathway from climatic change to ecosystem function.
KP: ROYALE-NATIONAL-PARK, ISLE-ROYALE, SEA OTTERS, MOOSE HERBIVORY,
BALSAM FIR, FOOD-WEB, WOLVES, COMMUNITY, VEGETATION, PREDATION
(9) TI: Multiple regimes in Northern Hemisphere height fields via
mixture model clustering
AU: Smyth,P, Ide,K, Ghil,M
NA: UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA,90095
UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS
ANGELES,CA,90095
UNIV CALIF IRVINE,DEPT INFORMAT & COMP SCI,IRVINE,CA,92717
JN: JOURNAL OF THE ATMOSPHERIC SCIENCES, 1999, Vol.56, No.21,
pp.3704-3723
IS: 0022-4928
DT: Article
AB: A mixture model is a flexible probability density estimation
technique, consisting of a linear combination of k component
densities. Such a model is applied to estimate clustering in
Northern Hemisphere (NH) 700-mb geopotential height anomalies.
A key feature of this approach is its ability to estimate a
posterior probability distribution for k, the number of
clusters given the data and the model. The number of clusters
that is most likely to fit the data is thus determined
objectively.
A dataset of 44 winters of NH 700-mb fields is projected onto
its two leading empirical orthogonal functions (EOFs) and
analyzed using mixtures of Gaussian components. Cross-validated
likelihood is used to determine the best value of k. the number
of clusters. The posterior probability so determined peaks at k
= 3 and thus yields clear evidence for three clusters in the NH
700-mb data. The three-cluster result is found to be robust
with respect to variations in data preprocessing and data
analysis parameters. The spatial patterns of the three
clusters' centroids bear a high degree of qualitative
similarity to the three clusters obtained independently by
Cheng and Wallace, using hierarchical clustering on 500-mb NH
winter data: the Gulf of Alaska ridge, the high over southern
Greenland, and the enhanced climatological ridge over the
Rockies.
Separating the 700-mb data into Pacific (PAC) and Atlantic
(ATL) sector maps reveals that the optimal k value is 2 for
both the PAC and ATL sectors. The respective clusters consist
of Kimoto and Ghil's Pacific-North American (PNA) and reverse
PNA regimes, as well as the zonal and blocked phases of the
North Atlantic oscillation. The connections between our
sectorial and hemispheric results are discussed from the
perspective of large-scale atmospheric dynamics.
KP: PROBABILITY DENSITY DISTRIBUTION, ATMOSPHERIC WAVE AMPLITUDE,
WEATHER REGIMES, FLOW REGIMES, WINTERTIME CIRCULATION,
OBSERVATIONAL EVIDENCE, PERSISTENT ANOMALIES, PREDICTABILITY,
OSCILLATION, TRANSITIONS
(10) TI: Climate change in Ireland from precipitation and streamflow
observations
AU: Kiely,G
NA: UNIV COLL CORK,DEPT CIVIL & ENVIRONM ENGN,CORK,IRELAND
JN: ADVANCES IN WATER RESOURCES, 1999, Vol.23, No.2, pp.141-151
IS: 0309-1708
DT: Article
AB: On the basis of General Circulation Model (GCM) experiments
with increased CO2, many parts of the northern latitudes
including western Europe, are expected to have enhanced
hydrologic cycles. Using observations of precipitation and
streamflow from Ireland, we test for climatic and hydrologic
change in this maritime climate of the northeast Atlantic. Five
decades of hourly precipitation (at eight sites) and daily
streamflow at four rivers in Ireland were investigated for
patterns of climate variability. An increase in annual
precipitation was found to occur after 1975. This increase in
precipitation is most noticeable on the West of the island.
Precipitation increases are significant in March and October
and are associated with increases in the frequency of wet hours
with no change in the hourly intensities. Analysis of
streamflow data shows the same trends. Furthermore, analysis of
extreme rainfall events show that a much greater proportion of
extremes have occurred in the period since 1975. A change also
occurred in the North Atlantic Oscillation (NAO) index around
1975. The increased NAO since 1975 is associated with increased
westerly airflow circulation in the Northeast Atlantic and is
correlated with the wetter climate in Ireland. These climatic
changes have implications for water resources management
particularly hood analysis and protection. (C) 1999 Elsevier
Science Ltd. All rights reserved.
KP: ATMOSPHERIC CIRCULATION PATTERNS, WESTERN UNITED-STATES,
STOCHASTIC-MODEL, HYDROLOGIC-CYCLE, RECENT TRENDS, TEMPERATURE,
OSCILLATION, SCOTLAND, PACIFIC, STATION
(11) TI: Variability of Fram Strait ice flux and North Atlantic
Oscillation (vol 104, pg 5177, 1999)
AU: Kwok,R, Rothrock,DA
JN: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1999, Vol.104, No.C10,
p.23615
IS: 0148-0227
DT: Correction or addition
(12) TI: Potential predictability of European winters from the analysis
of seasonal simulations with an AGCM
AU: Martineu,C, Caneill,JY, Sadourny,R
NA: EDF DIRECT ETUD & RECH,DEPT ENVIRONM,6 QUAI WATIER,F-78400
CHATOU,FRANCE
ECOLE NORMALE SUPER,CNRS,METEOROL DYNAM LAB,PARIS,FRANCE
JN: JOURNAL OF CLIMATE, 1999, Vol.12, No.10, pp.3033-3061
IS: 0894-8755
DT: Article
AB: The potential predictability of European winters on the
seasonal scale is investigated with the cycle 5.3 version of
the Laboratoire de Meteorologie Dynamique general circulation
model by analyzing the link between atmospheric low-frequency
variability and oceanic temperature prescribed as boundary
conditions. The word ''potential'' refers to the assumption
that the SST is a priori known in the experiments, and to the
use of a model to evaluate the real climate predictability.
Eleven simulations of the 1971-92 winters have been performed
with the model in SST-forced mode. The methodology used
identifies atmospheric clusters by Ward clustering scheme, and
atmospheric variability modes over Europe by matrix analysis of
relationships between variables. Tropical Pacific surface
temperature fluctuations play a prevailing role in the
modulation of European variability: the model preferentially
simulates negative phases of the North Atlantic Oscillation
during El Nino episodes, and a high pressure pattern in western
Europe during La Nina ones. These two situations are associated
with modulations in the structure of the North Atlantic jet and
of the North Atlantic storm track, in agreement with data
analyses synthesized in the literature. They confirm the
prevailing role of interactions between different scales of the
flow in the maintenance of persistent anomalies in the North
Atlantic/European area. The strong link simulated by the model
between the Pacific-North American oscillation and the North
Atlantic Oscillation plays an important role in the propagation
of the impact of the forcing from the tropical Pacific to the
North Atlantic.
For some winters (1971, 1984, 1989, and 1992, the number of
simulations has been increased to 30. The normality of the
simulated 1984 winter suggests a weak role of the tropical
Atlantic in specifying climate anomalies in Europe. The
differences in strength of the European response between the
1971 and 1989 La Nina events are linked to differences in the
Pacific/North American area. A stronger spread is found in the
El Nino case (1992 winter) than in the two La Nina cases. The
sensitivity of the response to the number of realizations
demonstrates that one has to reach about 15 simulations to
obtain a significant response over Europe.
KP: GENERAL-CIRCULATION MODEL, SEA-SURFACE TEMPERATURE,
EXTRATROPICAL SST ANOMALIES, ATMOSPHERIC VARIABILITY, SOUTHERN
OSCILLATION, NORTHERN-HEMISPHERE, ATLANTIC, PATTERNS, BLOCKING,
PACIFIC
(13) TI: Winter Atlantic climate and snowfall in the south and central
Appalachians
AU: Hartley,S
NA: MOREHEAD STATE UNIV,DEPT GEOG GOVT & HIST,MOREHEAD,KY,40351
JN: PHYSICAL GEOGRAPHY, 1999, Vol.20, No.1, pp.1-13
IS: 0272-3646
DT: Article
AB: Winter snowfall over much of the south and central Appalachian
region shows a significant inverse association with a winter
index of the North Atlantic Oscillation (NAO) teleconnection
pattern. The snowiest winters coincide with the negative phase
of this pattern. Composites of 700 mb heights over North
America and the adjacent Atlantic Ocean suggests that the
negative (positive) phase of the NAO results in anomalously
cool (warm) conditions across the region and this is confirmed
by examination of divisional temperatures, which are
significantly correlated (positive) with the NAO index. The
meridional circulation regime associated with the negative
phase of the NAO also results in a southward displacement of
the storm tracks across the eastern United States, as indicated
by composites of divisional precipitation and an index of
cyclonic activity. Snowfall shows significant correlation
(negative) with sea surface temperatures (SSTs) along the
northeast coast of the United States in both the
contemporaneous winter and preceding fall seasons, suggesting
that Atlantic SSTs may have some utility in winter forecasting.
KP: SEA-SURFACE TEMPERATURES, UNITED-STATES, TEMPORAL
CHARACTERISTICS, NORTHERN-HEMISPHERE, NEW-ENGLAND, VARIABILITY,
COVER, OSCILLATION, ASSOCIATION, EXTENT
WA: snowfall, Appalachians, winter climate, North Atlantic
Oscillation, Atlantic sea surface temperatures
(14) TI: Slope water current over the Laurentian Fan on interannual to
millennial time scales
AU: Keigwin,LD, Pickart,RS
NA: WOODS HOLE OCEANOG INST,WOODS HOLE,MA,02543
JN: SCIENCE, 1999, Vol.286, No.5439, pp.520-523
IS: 0036-8075
DT: Article
AB: The strength and position of surface and deep currents in the
slope water south of Newfoundland are thought to vary as a
coupled system in relation to the dipole in atmospheric sea
Level pressure known as the North Atlantic oscillation (NAO).
Paleoceanographic data from the Laurentian Fan, used as a proxy
for sea surface temperature. reveal that surface slope waters
north of the Gulf Stream experienced warming during the Little
Ice Age of the 16th to 19th centuries and support the notion of
an NAO-driven coupled system. The NAO may be a useful model for
millennial-scale ocean variability during interglacial climate
states.
KP: NORTH-ATLANTIC OSCILLATION, HOLOCENE, CIRCULATION, SEDIMENTS,
MARGIN
(15) TI: Precipitation over Greenland and its relation to the North
Atlantic Oscillation
AU: Bromwich,DH, Chen,QS, Li,YF, Cullather,RI
NA: OHIO STATE UNIV,BYRD POLAR RES CTR,POLAR METEOROL GRP,1090
CARMACK RD,COLUMBUS,OH,43210
OHIO STATE UNIV,DEPT GEOG,ATMOSPHER SCI
PROGRAM,COLUMBUS,OH,43210
JN: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1999, Vol.104,
No.D18, pp.22103-22115
IS: 0747-7309
DT: Article
AB: The omega equation method based on an equivalent isobaric
geopotential height in sigma coordinates has been used to
retrieve the precipitation over Greenland. This approach is
designed to accurately represent the topographic effects of the
Greenland Ice Sheet on atmospheric motion and precipitation.
The 11 year mean precipitation from 1985 to 1996 over all of
Greenland is 376 mm yr(-1), which is close to the long-term
mean precipitation of 346 mm yr(-1) estimated from
glaciological data. The precipitation over all of Greenland
shows that the largest value in 1986 is 472 mm yr(-1) and the
smallest value in 1995 is 309 mm yr(-1). The major interannual
variability of the atmospheric circulation in the North
Atlantic can be represented by the variation of the North
Atlantic Oscillation (NAO) index, which is most pronounced
during winter. It is found that if the NAO index increases, the
total precipitation over Greenland decreases, and vice versa.
The correlation coefficient between these two series for 1985-
1995 is -0.75. The mean precipitation over southern Greenland,
where the majority of precipitation falls, is more closely
related to the NAO index in winter, and their correlation
coefficient is -0.80. This relationship can be understood from
the composite maps of sea level pressure and Greenland
precipitation for the high and low index months. During months
of high NAO index values, the Icelandic Low is strong. During
months of low NAO index values, the monthly mean low is located
to the southwest of Greenland over the Labrador Sea.
Precipitation amounts over the southeast coast of Greenland are
about 100 mm larger during the low NAO index months than the
high NAO index months. Precipitation over all of Greenland
during the low NAO index months is higher. There are
significant downward trends in annual precipitation from 1985-
1995 for all of Greenland and its southern and central west
coastal regions, amounting to about 3% per year.
KP: ICE-SHEET, LIMITED-AREA, WINTER TEMPERATURES, HIGH-LATITUDES,
ACCUMULATION, VARIABILITY, CIRCULATION, HEMISPHERE, PROJECT,
CYCLONE
(16) TI: Multiscale variabilities in global sea surface temperatures and
their relationships with tropospheric climate patterns
AU: Enfield,DB, MestasNunez,AM
NA: NOAA,ATLANTIC OCEANOG & METEOROL LAB,4301 RICKENBACKER
CAUSEWAY,MIAMI,FL,33149
UNIV MIAMI,COOPERAT INST MARINE & ATMOSPHER
STUDIES,MIAMI,FL,33152
JN: JOURNAL OF CLIMATE, 1999, Vol.12, No.9, pp.2719-2733
IS: 0894-8755
DT: Article
AB: El Nino-Southern Oscillation (ENSO) is a global phenomenon with
significant phase propagation within and between basins. This
is captured and described in the first mode of a complex
empirical orthogonal function (CEOF) analysis of sea surface
temperature anomaly (SSTA) from the midnineteenth century
through 1991. The global ENSO from the SSTA data, plus a linear
trend everywhere, are subsequently removed in order to consider
other global modes of variability uncontaminated by the intra-
and interbasin effects of ENSO. An ordinary CEOF analysis of
the SSTA residuals reveals three non-ENSO modes of low-
frequency variability that are related to slow oceanic and
climate signals described in the literature. The first two
modes have decadal to multidecadal timescales with high
loadings in the Pacific. They bear some spatial similarities to
the ENSO pattern but are broader, more intense at high
latitudes, and differ in the time domain. A CEOF analysis
confirms that they are not merely the phase-related components
of a single mode and that all three modes are without
significant phase propagation. The third mode is a multidecadal
signal with maximal realization in the extratropical North
Atlantic southeast of Greenland. It is consistent with studies
that have documented connections between North Atlantic SSTA
and the tropospheric North Atlantic Oscillation (NAO).
All three SSTA modes have midtropospheric associations related
to previously classified Northern Hemisphere teleconnection
patterns. The relationships between SSTA modes and tropospheric
patterns are consistent with the ocean-atmosphere interactions
discussed in previous studies to explain low-frequency climate
oscillations in the North Pacific and North Atlantic sectors.
The first three leading modes of non-ENSO SSTA are most
related, to the tropospheric patterns of the Pacific North
American, the North Pacific, and the Arctic oscillations (AO),
respectively. The 500-hPa pattern associated with the third
SSTA mode also bears similarities to the NAO in its Atlantic
sector. This North Atlantic mode has a region of high, positive
SSTA loadings in the Gulf of Alaska, which appear to be
connected to the North Atlantic SSTA by a tropospheric bridge
effect in the AO.
KP: OCEAN-ATMOSPHERE MODEL, NORTH PACIFIC, EL-NINO, INTERDECADAL
VARIABILITY, GEOPOTENTIAL HEIGHT, SOUTH-ATLANTIC, SST ANOMALIES,
HEAT-FLUX, CIRCULATION, OSCILLATION
(17) TI: A comparison of decadal climate oscillations in the north
Atlantic detected in observations and a coupled GCM
AU: Watanabe,M, Kimoto,M, Nitta,T, Kachi,M
NA: UNIV TOKYO,CTR CLIMATE SYST RES,MEGURO KU,4-6-1 KOMABA,TOKYO
153,JAPAN
NATL SPACE DEV AGCY JAPAN,EARTH OBSERVAT RES CTR,TOKYO,JAPAN
JN: JOURNAL OF CLIMATE, 1999, Vol.12, No.9, pp.2920-2940
IS: 0894-8755
DT: Article
AB: Decadal climate variations in the Atlantic Ocean found in
observational fields and a coupled general circulation model
(CGCM) are investigated. In particular, physical processes
responsible for the phase reversal are compared.
Observed and modeled decadal variations have dominant
periodicities around 12.3 and 9.9 yr, respectively. Both
variations show similar spatial features: sea surface
temperature (SST) anomalies in the western subtropical Atlantic
sandwiched by those with opposite sign to the north and south,
and a dipole of sea level pressure anomalies, which resemble
the North Atlantic Oscillation. Their temporal evolutions are,
however, different from each other suggestive of different
dynamics of the oscillation. In the observations, SST and
surface-layer (0-100 m) temperature anomalies move eastward
from the subtropical western Atlantic to the European coast
along the Gulf Stream. Northward propagation of SST anomalies
are also found along the western boundaries including the Gulf
of Mexico. A budget analysis for the temperature equation shows
that these features are the manifestation of the advection of
SST anomalies by the mean current, which acts to switch one
phase of the oscillation to another. Anomalous gyre intensity
appears to have little contribution to the phase switching
process of the nearsurface variability, although the influence
of the anomalous gyre is found in the lower subsurface up to
500 m. In contrast, SST anomalies in the CGCM are more strongly
tied with subsurface temperature anomalies that propagate
westward, consistent with a slow gyre adjustment by the
baroclinic Rossby wave propagation. The wave-induced advection
acts to change the phase of SST as well as the subsurface
temperature anomalies in the model. Subduction of temperature
anomalies is found to occur on decadal timescales both in the
observation and in the model over the eastern basin where the
winter mixed layer is deepened, although the consequence of
such a process is not very clear.
In agreement with previous studies, it is suggested that the
atmosphere-ocean interaction is important for the decadal
variability. The anomalous heat Bur originated from the wind-
evaporation feedback appears to play a dominant role in the
formation of the tripolar structure of oceanic thermal
anomalies both in observations and in the CGCM. On the other
hand, the dominant timescales of observed and simulated decadal
modes are largely dominated by the mean subtropical gyre
velocity, and by the propagation speed of long Rossby waves,
respectively, both of which happen to have similar timescales.
KP: SEA-SURFACE TEMPERATURE, MULTIPLE TIME SCALES, INTERDECADAL
VARIABILITY, ATMOSPHERIC CIRCULATION, INTERANNUAL VARIABILITY,
PLANETARY-WAVES, PACIFIC-OCEAN, HEAT-FLUX, MODEL, ANOMALIES
(18) TI: Decadal and longer changes of the winter sea level pressure
fields and related synoptic activity over the North Atlantic
AU: Zveryaev,II
NA: UNIV HAWAII,IPRC,SOEST,MSB ROOM 227,1000 POPE
RD,HONOLULU,HI,96822
PP SHIRSHOV OCEANOL INST,MOSCOW,RUSSIA
UNIV HAWAII MANOA,INT PACIFIC RES CTR,HONOLULU,HI,96822
JN: INTERNATIONAL JOURNAL OF CLIMATOLOGY, 1999, Vol.19, No.11,
pp.1177-1185
IS: 0899-8418
DT: Article
AB: Long-term intensity changes in the winter synoptic activity
over the North Atlantic are studied in relation to changes of
the winter mean sea level pressure (SLP) fields. Analysis of
linear trends has revealed a good agreement between long-term
(interdecadal) changes in the intensity of synoptic processes
and variations of the winter SLP. On the contrary, no such
agreement was found between detrended and low-pass filtered
anomalies. There are periods, that are characterised by the
enhanced (reduced) synoptic activity attributed to the low
(high) index of the North Atlantic Oscillation (NAO). It
appears that low-passed anomalies of intramonthly root mean
square deviations (RMSD) of SLP are negatively correlated with
NAO and East Atlantic (EA) teleconnection patterns over most of
the North Atlantic. The low-passed winter SLP anomalies
demonstrate both propagating and standing patterns. The latter
have a period of about 8 years. While meridional dipole-like
structures formed by the winter SLP anomalies are shifted to
the west (east) of the North Atlantic, the related anomalies of
synoptic activity tend to be located in the eastern (western)
part of the region. When decadally averaged, anomalies in the
intensity of synoptic activity are strongly linked to the North
Atlantic storm track position. The exception is the 1980-1990
decade, characterised by a very high NAO index. During this
decade, enhanced synoptic activity is observed to the south of
the North Atlantic storm track. Copyright (C) 1999 Royal
Meteorological Society.
KP: SURFACE-TEMPERATURE, CLIMATE VARIABILITY, OSCILLATION,
PRECIPITATION, CIRCULATION, TRENDS, EUROPE, OCEAN
WA: North Atlantic ocean, sea level pressure, North Atlantic
Oscillation (NAO), climatic changes, winter anomalies, linear
trends, low-pass filtering, correlation analysis
(19) TI: European surface pressure patterns for months with outstanding
climatic anomalies during the sixteenth century
AU: Jacobeit,J, Wanner,H, Koslowski,G, Gudd,M
NA: UNIV WURZBURG,INST GEOG,AM HUBLAND,D-97074 WURZBURG,GERMANY
UNIV BERN,INST GEOG,CH-3012 BERN,SWITZERLAND
JN: CLIMATIC CHANGE, 1999, Vol.43, No.1, pp.201-221
IS: 0165-0009
DT: Article
AB: Monthly mean surface pressure patterns in the European area are
reconstructed for those winter and summer seasons of the 16th
century with outstanding climatic anomalies being either
widespread over Europe or remarkably intensive in some European
regions. From the available documentary information about
weather characteristics and their sequences, it proved possible
to infer prevalent processes of lower tropospheric advection of
typical air masses and to assess the position and strength of
major surface pressure centres on a monthly scale. For
comparison with modem pressure patterns, monthly mean sea level
pressure(SLP) grids from the 20th century have been selected
for seasons with similar climatic anomalies. There are broad
coincidences between these pressure patterns of the 16th and
the 20th centuries except for cold summer seasons. Finally,
results from the 16th century are discussed in terms of
circulation dynamics (different phases of the North Atlantic
Oscillation (NAO) in winter, decreasing frequency of
anticyclonic ridging in summer).
KP: ATLANTIC, CIRCULATION, TEMPERATURE
(20) TI: Evaluation of the North Atlantic Oscillation as simulated by a
coupled climate model
AU: Osborn,TJ, Briffa,KR, Tett,SFB, Jones,PD, Trigo,RM
NA: UNIV E ANGLIA,CLIMAT RES UNIT,NORWICH NR4 7TJ,NORFOLK,ENGLAND
METEOROL OFF,HADLEY CTR CLIMATE PREDICT &
RES,BRACKNELL,BERKS,ENGLAND
JN: CLIMATE DYNAMICS, 1999, Vol.15, No.9, pp.685-702
IS: 0930-7575
DT: Article
AB: The realism of the Hadley Centre's coupled climate model
(HadCM2) is evaluated in terms of its simulation of the winter
North Atlantic Oscillation (NAO), a major natural mode of the
Northern Hemisphere atmosphere that is currently the subject of
considerable scientific interest. During 1400 y of a control
integration with present-day radiative forcing levels, HadCM2
exhibits a realistic NAO associated with spatial patterns of
sea level pressure, synoptic activity, temperature and
precipitation anomalies that are very similar to those
observed. Spatially, the main model deficiency is that the
simulated NAO has a teleconnection with the North Pacific that
is stronger than observed. In a temporal sense the simulation
is compatible with the observations if the recent observed
trend (from low values in the 1960s to high values in the early
1990s) in the winter NAO index (the pressure difference between
Gibraltar and Iceland) is ignored. This recent trend is,
however, outside the range of variability simulated by the
control integration of HadCM2, implying that either the model
is deficient or that external forcing is responsible for the
variation. It is shown, by analysing two ensembles, each of
four HadCM2 integrations that were forced with historic and
possible future changes in greenhouse gas and sulphate aerosol
concentrations, that a small part of the recent observed
variation may be a result of anthropogenic forcing. If so, then
the HadCM2 experiments indicate that the anthropogenic effect
should reverse early next century, weakening the winter
pressure gradient between Gibraltar and Iceland. Even combining
this anthropogenic forcing and internal variability cannot
explain all of the recent observed variations, indicating
either some model deficiency or that some other external
forcing is partly responsible.
KP: SURFACE-TEMPERATURE, ATMOSPHERIC CIRCULATION, SOUTHERN
OSCILLATION, EL-NINO, VARIABILITY, HEMISPHERE, EUROPE, OCEAN,
GCM, PRECIPITATION
(21) TI: On the connection between upper atmospheric dynamics and
tropospheric parameters: Correlations between mesopause region
winds and the North Atlantic Oscillation
AU: Jacobi,C, Beckmann,BR
NA: UNIV LEIPZIG,INST METEOROL,STEPHANSTR 3,D-04103 LEIPZIG,GERMANY
JN: CLIMATIC CHANGE, 1999, Vol.43, No.3, pp.629-643
IS: 0165-0009
DT: Article
AB: The middle- and high-latitude stratospheric and mesospheric
wind field in winter is dominated by the stratospheric polar
vortex, which reaches up into the mesopause region and leads to
westerly winds there in winter. The tropospheric mean winter
wind field is also connected with the stratospheric polar
vortex, which thus can be considered as extending from the
lower up to the upper atmosphere. We found that the January and
February zonal winds of the mesopause region, as measured at
the Collm Observatory of the University of Leipzig, are closely
connected with the North Atlantic Oscillation (NAO) which can
be considered as a measure for part of the northern hemispheric
mean circulation in the Atlantic and Europe domain, since it
influences the circulation over that domain. The NAO itself is
considered to be a measure for Central Europe winter winds and
temperatures, since large NAO indices are connected with
stronger westerlies in Central Europe. Thus, the mesopause
region winds are also positively correlated to the Central
European winter surface temperatures.
KP: CENTRAL-EUROPE, STRATOSPHERIC CIRCULATION, WINTER, TEMPERATURES,
HEMISPHERE, WARMINGS, FIELD, COLLM
(22) TI: Extrinsic modification of vertebrate sex ratios by climatic
variation
AU: Post,E, Forchhammer,MC, Stenseth,NC, Langvatn,R
NA: UNIV OSLO,DEPT BIOL,DIV ZOOL,POB 1050,BLINDERN,N-0316
OSLO,NORWAY
UNIV OSLO,DEPT BIOL,DIV ZOOL,N-0316 OSLO,NORWAY
UNIV CAMBRIDGE,DEPT ZOOL,LARGE ANIM RES GRP,CAMBRIDGE CB4
3EJ,ENGLAND
NATL ENVIRONM RES INST,DEPT LANDSCAPE ECOL,POPULAT ECOL GRP,DK-
8410 KALO,DENMARK
UNIV STUDIES SVALBARD,N-9170 LONGYEARBYEN,SPRITZBERGEN,NORWAY
JN: AMERICAN NATURALIST, 1999, Vol.154, No.2, pp.194-204
IS: 0003-0147
DT: Article
AB: Evidence for the influences of climate on early development,
maternal condition, and offspring viability in terrestrial
vertebrates suggests that climatic change has the potential to
induce variation in offspring sex ratios in such organisms.
Using long-term data at individual and population levels, we
investigated the influence of global climatic variation, as a
result of the North Atlantic Oscillation (NAO), on offspring
sex ratios of red deer in Norway. The state of the NAO during
the fetal development of hinds influenced the mass of their
sons, but not daughters, and increasingly warmer and snowy
winters led to increasingly male-biased offspring sex ratios,
independently of changes in the mean age of hinds. Moreover,
hinds that were themselves born following warm, snowy winters
were smaller as adults, produced significantly lighter sons,
and tended to produce more sons than hinds born following cold,
dry winters. In light of the fact that these observations defy
explanation according to previous hypotheses of adaptive
modification of offspring sex ratios, we present the extrinsic
modification hypothesis, which suggests that sex ratios may
evolve in variable environments through natural selection
independently of maternal strategies of sex allocation.
KP: LOCAL RESOURCE COMPETITION, NORTH-ATLANTIC OSCILLATION, DEER
CERVUS-ELAPHUS, RED DEER, POPULATION-DYNAMICS, PARENTAL
INVESTMENT, BREEDING SUCCESS, MAMMALS, BIRTH, REPRODUCTION
WA: Cervus elaphus, environment, fitness, maternal effects, sex
ratio evolution
(23) TI: Dominant patterns of climate variability in the Atlantic Ocean
during the last 136 years
AU: Tourre,YM, Rajagopalan,B, Kushnir,Y
NA: COLUMBIA UNIV,LAMONT DOHERTY EARTH OBSERV,POB 1000,RT
9W,PALISADES,NY,10964
JN: JOURNAL OF CLIMATE, 1999, Vol.12, No.8 Pt1, pp.2285-2299
IS: 0894-8755
DT: Review
AB: Dominant spatiotemporal patterns of joint sea surface
temperature (SST) and sea level pressure (SLP) variability in
the Atlantic Ocean are identified using a multivariate
frequency domain analysis. Five significant frequency bands are
isolated ranging from the quasi biennial to the quasi decadal.
Two quasi-biennial bands are centered around 2.2- and 2.7-yr
periods: two interannual bands are centered around 3.5- and
4.4-yr periods; the fifth band at the quasi-decadal frequency
is centered around 11.4-yr period. Between 1920 and 1955, the
quasi-decadal band is less prominent compared to the quasi-
biennial bands. This happens to be the period when SLP
gradually increased over the Greenland-Iceland regions. The
spatial pattern at the quasi-decadal frequency displays an out-
of-phase relationship in the SLP in the vicinity of the
subtropical anticyclones in both hemispheres (indicative of an
out-of-phase quasi-decadal variability in the North and South
Atlantic Hadley circulation). The quasi-decadal frequency also
displays an out-of-phase relationship in the SSTs north and
south of the mean position of the intertropical convergence
zone (ITCZ). This short-lived structure, lasting for
approximately two years, supports the argument that a tropical
SST dipole pattern is one of the characteristics of the quasi-
decadal signal. All five frequency bands represent to some
extent fluctuations of the North Atlantic oscillation and are
associated with tropical Atlantic Ocean warming (cooling) with
different spatial evolution. The two interannual bands show
opposite SST evolution to the south of the ITCZ, that is,
southeastward evolution from the western tropical Atlantic for
the 3.5-yr period and westward spreading from the eastern
tropical Atlantic for the 4.4-yr period. Moreover, a
significant coherence (with a 1-yr phase lag) is found between
the SST time series along the equatorial Atlantic obtained from
the 3.5-yr period, and the SST time series in the NINO3 area in
the Pacific. It is cautiously argued that the 3.5-yr period is
largely associated with the global El Nino-Southern Oscillation
phenomenon. while the evolution of the 4.4-yr period depends
more upon Atlantic local conditions.
KP: SEA-SURFACE TEMPERATURE, EXTRATROPICAL SST ANOMALIES, ANTARCTIC
CIRCUMPOLAR WAVE, NINO-SOUTHERN OSCILLATION, GENERAL-
CIRCULATION MODEL, PROGRAM FRANCAIS OCEAN, TROPICAL ATLANTIC,
NORTH-ATLANTIC, EL-NINO, EQUATORIAL ATLANTIC
(24) TI: The atmospheric response over the North Atlantic to decadal
changes in sea surface temperature
AU: Venzke,S, Allen,MR, Sutton,RT, Rowell,DP
NA: MAX PLANCK INST METEOROL,BUNDESSTR 55,D-20146 HAMBURG,GERMANY
UNIV OXFORD,OXFORD,ENGLAND
RUTHERFORD APPLETON LAB,DEPT SPACE SCI,CHILTON,ENGLAND
UNIV READING,DEPT METEOROL,READING,BERKS,ENGLAND
METEOROL OFF,HADLEY CTR CLIMATE PREDICT & RES,BRACKNELL RB12
2SZ,BERKS,ENGLAND
JN: JOURNAL OF CLIMATE, 1999, Vol.12, No.8 Pt2, pp.2562-2584
IS: 0894-8755
DT: Article
AB: Decadal fluctuations in the climate of the North Atlantic-
European region may be influenced by interactions between the
atmosphere and the Atlantic Ocean, possibly as parr of a
coupled ocean-atmosphere mode of variability. For such a mode
to exist, a consistent atmospheric response to fluctuations in
North Atlantic sea surface temperatures (SST) is required.
Furthermore, this response must provide feedbacks to the ocean.
Whether a consistent response exists, and whether it yields the
required feedbacks, are issues that remain controversial. Here.
these issues are addressed using a novel approach to analyze an
ensemble of six integrations of the Hadley Centre atmospheric
general circulation model HadAM1, all forced with observed
global SSTs and sea-ice extents for the period 1949-93.
Characterizing the forced atmospheric response is complicated
by the presence of internal variability. A generalization of
principal component analysis is used to estimate the common
forced response given the knowledge of internal variability
provided by the ensemble. In the North Atlantic region a remote
atmospheric response to El Nino-Southern Oscillation and a
further response related to a tripole pattern in North Atlantic
SST are identified. The latter, which is most consistent in
spring, involves atmospheric circulation changes over the
entire region, including a dipole pattern in sea level pressure
often associated with the North Atlantic oscillation. Only over
the tropical/subtropical Atlantic, however, does it account for
a substantial fraction of the total variance. How the
atmospheric response could feed back to affect the ocean, and
in particular the SST tripole, is investigated. Several
potential feedbacks are identified but it has to be concluded
that, because of their marginal consistency between ensemble
members, a coupled mode that relied on these feedbacks would be
susceptible to disruption by internal atmospheric variability
Notwithstanding this conclusion, the authors results suggest
that predictions of SST evolution could be exploited to predict
some aspects of atmospheric variability over the North
Atlantic, including fluctuations in spring of the subtropical
trade winds and the higher latitude westerlies.
KP: CLIMATE-CHANGE, SEASONAL PREDICTABILITY, GENERAL-CIRCULATION,
FINGERPRINT METHOD, SOLAR IRRADIANCE, GCM SIMULATIONS, SST
ANOMALIES, VARIABILITY, OCEAN, MODEL
(25) TI: Interannual to decadal predictability in a coupled ocean-
atmosphere general circulation model
AU: Grotzner,A, Latif,M, Timmermann,A, Voss,R
NA: MAX PLANCK INST METEOROL,BUNDESSTR 55,D-20146 HAMBURG,GERMANY
DEUTSCH KLIMARECHENZENTRUM,HAMBURG,GERMANY
JN: JOURNAL OF CLIMATE, 1999, Vol.12, No.8 Pt2, pp.2607-2624
IS: 0894-8755
DT: Article
AB: The predictability of the coupled ocean-atmosphere climate
system on interannual to decadal timescales has been studied by
means of ensemble forecast experiments with a global coupled
ocean-atmosphere general circulation model. Over most parts of
the globe the model's predictability can be sufficiently
explained by damped persistence as expected from the stochastic
climate model concept with damping times of considerably less
than a year. Nevertheless, the tropical Pacific and the North
Atlantic Ocean exhibit oscillatory coupled ocean-atmosphere
modes, which lead to longer predictability timescales. While
the tropical mode shares many similarities with the observed
ENSO phenomenon, the coupled mode within the North Atlantic
region exhibits a typical period of about 30 yr and relies on
an interaction of the oceanic thermohaline circulation and the
atmospheric North Atlantic oscillation. The model's ENSO-like
oscillation is predictable up to one-third to one-half (2-3 yr)
of the oscillation period both in the ocean and the atmosphere.
The North Atlantic yields considerably longer predictability
timescales (of the order of a decade) only for quantities
describing the model's thermohaline circulation. For surface
quantities and atmospheric variables only marginal
predictability (of the order of a year) was obtained. The
predictability of the coupled signal at the surface is
destroyed by the large amount of internally generated (weather)
noise. This is illustrated by means of a simple conceptual
model for coupled ocean-atmosphere variability and
predictability.
KP: MULTIDECADAL CLIMATE VARIABILITY, NORTH-ATLANTIC OCEAN,
THERMOHALINE CIRCULATION, INTERDECADAL VARIATIONS, SEA,
TEMPERATURE, SIMULATION, OSCILLATOR, ENSO
(26) TI: Reconstruction of monthly NAO and EU indices back to AD 1675
AU: Luterbacher,J, Schmutz,C, Gyalistras,D, Xoplaki,E, Wanner,H
NA: UNIV BERN,INST GEOG,HALLERSTR 12,CH-3012 BERN,SWITZERLAND
UNIV THESSALONIKI,DEPT METEOROL & CLIMATOL,GR-54006
THESSALONIKI,GREECE
JN: GEOPHYSICAL RESEARCH LETTERS, 1999, Vol.26, No.17, pp.2745-2748
IS: 0094-8276
DT: Article
AB: Instrumental station pressure, temperature and precipitation
measurements and proxy data were used to Statistically
reconstruct monthly time series of the North Atlantic
Oscillation (NAO) and the Eurasian (EU) circulation indices
back to 1675. Systematic testing of the reconstruction
procedure indicated generally reliable reconstructions
throughout the entire period, except for summertime before
about 1750. Predictive skill varied for different sub-periods
depending on data availability. It was highest for autumn and
winter and was generally better for the EU than for the NAO
index. Wavelet analysis suggested significant low-frequency
variability, especially for the spring, summer and annual
averaged indices. The co-variability between the NAO and EU
indices was found to exhibit large decadal to century timescale
variations, indicating that climate variability over the
continent is temporarily decoupled from the NAG.
KP: NORTH-ATLANTIC OSCILLATION, HEMISPHERE WINTER, TEMPERATURES
(27) TI: Ice break-up on southern Lake Baikal and its relationship to
local and regional air temperatures in Siberia and to the North
Atlantic Oscillation
AU: Livingstone,DM
NA: SWISS FED INST ENVIRONM SCI & TECHNOL,DEPT ENVIRONM
PHYS,UBERLANDSTR 133,CH-8600 DUBENDORF,SWITZERLAND
JN: LIMNOLOGY AND OCEANOGRAPHY, 1999, Vol.44, No.6, pp.1486-1497
IS: 0024-3590
DT: Article
AB: The calendar date of ice break-up on southern Lake Baikal has
been recorded uninterruptedly since 1869. A strong trend to
earlier thawing up to around 1920 (1 d per 3.3 yr) is followed
by the lack of any significant trend thereafter. For the period
1931-1994, the timing of break-up is related to local surface
air temperatures integrated over periods of 1-3 months.
Although highest unimodal correlations an with the 3-month mean
air temperature, a bimodal relationship between break-up and
air temperature exists at shorter integration times, with
break-up date being related not only to the air temperature
prevailing during thawing (April) but also to that prevailing
during the time of ice formation, when air temperatures are
lowest (February). High-frequency (interannual) fluctuations in
the timing of break-up appear to be influenced mainly by the
air temperatures prevailing during thawing, and low-frequency
(interdecadal) fluctuations by those prevailing during ice
formation.
Whereas correlations with April air temperatures are always
significant, those with February air temperatures an only
significant during the latter part of this century, i.e., after
cessation of the tendency toward earlier thawing. The high
correlation between break-up date and integrated air
temperature is not merely local but extends over most of
Siberia and parts of northern China. Because air temperatures
in Siberia contain a strong winter NAO (North Atlantic
Oscillation) signal, so does the Lake Baikal break-up date,
with up to 14% of the variance in the observed date of break-up
being explained by the seasonal NAO index from January to
March. As in the case of the air temperature data, a
significant NAO signal in the break-up date can be detected
only during the latter part of this century, implying that the
influence of the NAO on the thawing of Lake Baikal during the
early part of this century was probably negligible.
KP: MOUNT-PINATUBO ERUPTION, SEVERITY INDEX, CLIMATE,
TELECONNECTIONS, WISCONSIN, WINTER, FREQUENCY, RECORDS, TRENDS,
SEASON
(28) TI: The influence of the North Atlantic Oscillation on the regional
temperature variability in Sweden: spatial and temporal
variations
AU: Chen,DL, Hellstrom,C
NA: UNIV GOTHENBURG,DEPT EARTH SCI,BOX 460,S-40530
GOTHENBURG,SWEDEN
JN: TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY, 1999,
Vol.51, No.4, pp.505-516
IS: 0280-6495
DT: Article
AB: A statistical analysis of the seasonal and interannual
variations in the regional temperature anomalies of Sweden
during 1861-1994 is performed. The study uses homogenized
monthly temperatures averaged over 6 regions to minimize the
non-climatic and local-scale climatic effects. It is found that
the temperature variability shows a clear regional and seasonal
dependency. The topography, the influence of the sea acid the
synoptic climatology may have determined the dependency. The
anomaly is related to variations in the North Atlantic
Oscillation (NAO) expressed by an index (NAOI) and the extent
to which the temperature anomaly can be explained by the NAO is
investigated. The results show that the NAO has an important
effect on the regional Swedish temperature on the monthly and
interannual scales. The relationship between the temperature
and NAOI over the period 1985-1994 are strong, implying that
the NAOI may be a suitable candidate for a statistical
downscaling model of the regional temperature. However,
correlation analysis over different 31-year periods shows that
the strength of the association varies with time and region.
The further north the weaker the association. On the other
hand, the temporal variations of the moving correlations for
the 6 regions are similar. Part of the temporal variations may
be explained by the averaged strength of NAO during different
31-year periods. This is especially evident for southern
Sweden. At last, the coherency spectrums between the
temperature anomalies acid the NAO index is determined, which
enables an examination of the association over the frequency
domain. The result supports the idea that the NAO has an
important effect on the Swedish temperature, though the
strength of the association varied with rime. These results
have implications for statistical downscaling.
KP: AIR-TEMPERATURE, ATMOSPHERIC CIRCULATION, GEOGRAPHICAL-
DISTRIBUTION, SOUTHERN OSCILLATION, GEOPOTENTIAL HEIGHT, WINTER
TEMPERATURES, ZONAL INDEX, EUROPE, PERSISTENCE, SEASONALITY
(29) TI: A wavelet characterization of the North Atlantic oscillation
variation and its relationship to the North Atlantic sea
surface temperature
AU: Higuchi,K, Huang,JP, Shabbar,A
NA: ATMOSPHER ENVIRONM SERV,CARBON CYCLE RES LAB,AIR QUAL LAB,4905
DUFFERIN ST,TORONTO,ON M3H 5T4,CANADA
JN: INTERNATIONAL JOURNAL OF CLIMATOLOGY, 1999, Vol.19, No.10,
pp.1119-1129
IS: 0899-8418
DT: Article
AB: In this study, Multiresolution Fourier Transform (MFT) spectral
analysis is employed to resolve the temporal structure of the
variation of the North Atlantic Oscillation (NAO) in terms of
various frequency components. The NAO index displays
fluctuations on multiple timescales, resulting in an MFT
spectrum characterized by the occurrences of distinct frequency
bands at certain times in the record. These frequency bands are
examined within the context of annual to interdecadal spectral
components. The relative contribution by each of these spectral
components toward the overall NAO variability varies with time.
Phase analysis of the spectrum demonstrates that, in addition
to some apparent 'random' fluctuations, the phase of each of
the spectral components on occasions exhibits relatively
constant value over a period of time (from a few years to a
decade). In addition, a significant coherent relationship
between the NAO and the North Atlantic sea surface temperature
(SST) is found at interannual and interdecadal timescales. Some
evidence has also been found to suggest that the phase of the
interdecadal component of the NAO is itself modulated by the
North Atlantic SST at a timescale of about 60 years. Copyright
(C) 1999 Royal Meteorological Society.
KP: MULTIRESOLUTION FOURIER-TRANSFORM, ATMOSPHERIC CIRCULATION,
SOUTHERN OSCILLATION, WINTER TEMPERATURES, GREENLAND, EUROPE,
FLUCTUATIONS, ASSOCIATION, HEMISPHERE, SEESAW
WA: North Atlantic Ocean, wavelet analysis, North Atlantic
Oscillation, North Atlantic SST, interannual and
intervariability, Multiresolution Fourier Transform spectral
analysis
(30) TI: Common dynamic structure of Canada lynx populations within
three climatic regions
AU: Stenseth,NC, Chan,KS, Tong,H, Boonstra,R, Boutin,S, Krebs,CJ,
Post,E, ODonoghue,M, Yoccoz,NG, Forchhammer,MC, Hurrell,JW
NA: NORWEGIAN ACAD SCI & LETTERS,CTR ADV STUDY,DRAMMENSVEIEN 78,N-
0271 OSLO,NORWAY
UNIV OSLO,DEPT BIOL,DIV ZOOL,N-0316 OSLO,NORWAY
UNIV IOWA,DEPT STAT & ACTUARIAL SCI,IOWA CITY,IA,52242
LONDON SCH ECON,DEPT STAT,LONDON WC2A 2AE,ENGLAND
UNIV HONG KONG,DEPT STAT,HONG KONG,HONG KONG
UNIV TORONTO,DIV LIFE SCI,SCARBOROUGH,ON M1C 1A4,CANADA
UNIV ALBERTA,DEPT BIOL SCI,EDMONTON,AB T6G 2E9,CANADA
UNIV BRITISH COLUMBIA,DEPT ZOOL,VANCOUVER,BC V6T 1Z4,CANADA
DEPT RENEWABLE RESOURCES,FISH & WILDLIFE BRANCH,MAYO,YT Y0B
1M0,CANADA
NORWEGIAN INST NAT RES,POLAR ENVIRONM CTR,DEPT ARCTIC ECOL,N-
9296 TROMSO,NORWAY
UNIV CAMBRIDGE,DEPT ZOOL,CAMBRIDGE CB2 3EJ,ENGLAND
NATL ENVIRONM RES INST,DEPT LANDSCAPE ECOL,DK-8410
RONDE,DENMARK
NATL CTR ATMOSPHER RES,CLIMATE ANAL SECT,BOULDER,CO,80307
JN: SCIENCE, 1999, Vol.285, No.5430, pp.1071-1073
IS: 0036-8075
DT: Article
AB: Across the boreal forest of Canada, Lynx populations undergo
regular density cycles. Analysis of 21 time series from 1821
onward demonstrated structural similarity in these cycles
within large regions of Canada. The observed population
dynamics are consistent with a regional structure caused by
climatic features, resulting in a grouping of Lynx population
dynamics into three types (corresponding to three climatic-
based geographic regions): Pacific-maritime, Continental, and
Atlantic-maritime. A possible Link with the North Atlantic
Oscillation is suggested.
KP: TELECONNECTIONS, DEER
(31) TI: A shift of the NAO and increasing storm track activity over
Europe due to anthropogenic greenhouse gas forcing
AU: Ulbrich,U, Christoph,M
NA: UNIV COLOGNE,INST GEOPHYS & METEOROL,D-50923 COLOGNE,GERMANY
MAX PLANCK INST METEOROL,D-20146 HAMBURG,GERMANY
JN: CLIMATE DYNAMICS, 1999, Vol.15, No.7, pp.551-559
IS: 0930-7575
DT: Article
AB: In accordance with a number of other general circulation model
experiments, the coupled atmosphere-ocean-GCM ECHAM4+OPYC3
simulates increasing upper air storm track activity over the
east Atlantic and Western Europe with rising greenhouse gas
forcing. This paper addresses the question to what extent this
change is attributable to the variable north Atlantic
Oscillation (NAO), which is closely related to the intensity of
the Atlantic storm track's extension into Europe. The NAO
index, which is based on sea level pressure fluctuations over
the north Atlantic in the 300-y control run of this model, only
shows a moderate increase within the 240-y scenario run, so
that its longterm trend does not exceed the variability of the
control climate before the end of the simulation. In contrast,
the steadily growing storm track activity over northwestern
Europe already surpasses the standard deviation defined from
the control run after about 160 y. This effect is associated
with a change of the NAO pattern. A determination of the
centres of action for subsequent 10-y periods based on
empirical orthogonal functions shows a systematic northeastward
shift of the NAO's northern variability centre from a position
close to the east coast of Greenland, where it is also located
in the control run, to the Norwegian Sea.
KP: NORTH-ATLANTIC OSCILLATION, SURFACE-TEMPERATURE, ATMOSPHERIC
CIRCULATION, GEOPOTENTIAL HEIGHT, HEMISPHERE WINTER, CLIMATE-
CHANGE, VARIABILITY, MODEL, PRECIPITATION, PATTERNS
(32) TI: Variations of precipitation and evaporation over the North
Atlantic Ocean, 1958-1997
AU: Walsh,JE, Portis,DH
NA: UNIV ILLINOIS,DEPT ATMOSPHER SCI,105 S GREGORY
AVE,URBANA,IL,61801
JN: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1999, Vol.104,
No.D14, pp.16613-16631
IS: 0747-7309
DT: Article
AB: The output from recent atmospheric reanalysis projects at the
National Centers for Environmental Prediction and the European
Centre for Medium-Range Weather Forecasts is used to address
regional and temporal variability of precipitation P and
evaporation E over the North Atlantic. The difference between P
and E is the net surface freshwater flux, which directly
affects the salinity and hence the stratification of the ocean
surface layer. Over North Atlantic subregions, spanning 10
degrees-15 degrees latitude and 30 degrees-40 degrees
longitude, the area-averaged P from the two reanalyses are
highly correlated with each other outside of the tropics and
are consistent with climatologies compiled from ship data. In
the annual mean, P exceeds E in the North Atlantic poleward of
50 degrees N; E exceeds P between 20 degrees N and 50 degrees N
and also in the eastern tropical North Atlantic (10 degrees N-
35 degrees N). Seasonality varies considerably among the
subregions: P and E both peak during late autumn/early winter
in the subpolar regions, and P has an autumn peak in the
subtropics, where E shows little seasonality. The year-to-year
variations of monthly and annual regional values are larger for
P than for E, implying that the interannual variations of P
minus E are driven primarily by P. These interannual variations
are sufficiently large and persistent that they can account for
substantial portions (0.1-1.0 salinity unit (SU) per year) of
observed salinity variations in the North Atlantic surface
waters. Atmospheric forcing of regional P shows consistent
teleconnections throughout the year, although the patterns are
strongest in winter and weakest in summer. The North Atlantic
Oscillation (NAO) is the dominant pattern controlling P in the
eastern and northern North Atlantic; P in the western North
Atlantic shows associations with the atmospheric circulation as
far away as the North Pacific. P anomalies of >3 cm month(-1)
are associated with multiyear periods of positive and negative
NAG. The high-NAG regime of the late 1980s and early 1990s has
coincided with increased P over the northeastern North Atlantic
and decreased P over the southwestern North Atlantic although
the seasonality of the NAO impact varies widely among the
regions.
KP: SEA-SURFACE TEMPERATURE, FRESH-WATER, INTERDECADAL VARIATIONS,
LABRADOR SEAS, GREENLAND, ICE, CIRCULATION, OSCILLATION,
ANOMALIES, SALINITY
(33) TI: The influence of year-to-year variations in winter weather on
the dynamics of Daphnia and Eudiaptomus in Esthwaite Water,
Cumbria
AU: George,DG, Hewitt,DP
NA: INST FRESHWATER ECOL,WINDERMERE LA22 0LP,CUMBRIA,ENGLAND
JN: FUNCTIONAL ECOLOGY, 1999, Vol.13, No.S1, pp.45-54
IS: 0269-8463
DT: Article
AB: 1. Micro-crustacea of the genus Daphnia and Eudiaptomus have
evolved different physiological mechanisms for coping with
lift: in a rapidly changing environment. In this paper, we
analyse some of the physical and biological factors influencing
the winter abundance of the two species in a small lake
(Esthwaite Water in Cumbria).
2, The results demonstrate that much of the year-to-year
variation in their relative abundance can be related to long-
term changes in the weather. The highest numbers of Daphnia
were typically found in cold, calm winters when small
flagellates were relatively abundant. In contrast, the highest
numbers of Eudiaptomus were found in mild, windy winters when
the phytoplankton community was dominated by colonial diatoms.
3, Year-to-year variations in the winter abundance of
Eudiaptomus had no effect on their subsequent development but
the numbers of overwintering Daphnia had a significant effect
on the size of their first spring 'cohort'. The most important
factor influencing the overwintering performance of the two
species was the water temperature.
4. Winter air temperatures over much of Europe are influenced
by the atmospheric pressure variation known as the North
Atlantic Oscillation (NAO). Winter water temperatures in
Esthwaite Water were strongly correlated with this empirical
index and there was a significant positive correlation between
the NAO and the number of overwintering Eudiaptomus.
KP: NORTH-ATLANTIC OSCILLATION, GULF-STREAM, LONG-TERM, LAKE,
PRECIPITATION, RESPIRATION
WA: winter weather, North Atlantic Oscillation, population dynamics,
Daphnia, Eudiaptomus
(34) TI: Tropical-extratropical connection in the Atlantic atmosphere-
ocean variability
AU: Watanabe,M, Kimoto,M
NA: UNIV TOKYO,CTR CLIMATE SYST RES,MEGURO KU,4-6-1 KOMABA,TOKYO
1538904,JAPAN
JN: GEOPHYSICAL RESEARCH LETTERS, 1999, Vol.26, No.15, pp.2247-2250
IS: 0094-8276
DT: Article
AB: A question how sea surface temperature (SST) fluctuations in
the tropical Atlantic affect the North Atlantic atmosphere-
ocean system is addressed using an atmospheric general
circulation model coupled to a 50-m-deep slab ocean (MGCM), and
a linear baroclinic model. A comparison of a 60-yr integration,
in which the tropical SSTs are prescribed to observations
(TOGA-ML), with the control MGCM run shows that the tropical
SST variations selectively enhance variance of the North
Atlantic Oscillation (NAO) by about 80%. This is partly due to
extratropical height anomalies associated with two dominant
modes, monopole and dipole, of tropical Atlantic SST
variability because they both have a projection on to the NAO
in the TOGA-ML run. The simulated midlatitude height anomalies
accompany characteristic SST anomaly patterns beneath, and they
are consistent with observations. Analyses of steady linear
responses to the heating in the tropical Atlantic and transient
eddy feedback in midlatitude reveal that the substantial part
of height anomalies is generated by the latter rather than the
former. The anomalous eddy forcing is, however, organized not
only by the heating in the tropical Atlantic but also by the
tropical Pacific SST variations through the teleconnection over
North America. It is suggested that the tropical Atlantic SST
variability does affect the North Atlantic atmosphere and
ocean, but the dynamical connection is tenuous in comparison
with the Pacific.
KP: EL-NINO, OSCILLATION, TRANSIENTS
(35) TI: Multidecadal global and regional trends in 1000 mb and 500 mb
cyclone frequencies
AU: Key,JR, Chan,ACK
NA: BOSTON UNIV,DEPT GEOG,675 COMMONWEALTH AVE,BOSTON,MA,02215
JN: GEOPHYSICAL RESEARCH LETTERS, 1999, Vol.26, No.14, pp.2053-2056
IS: 0094-8276
DT: Article
AB: Trends in seasonal and annual frequencies of 1000 mb and 500 mb
closed low pressure centers, or ''cyclones'', over the 40 year
period 1958-1997 are determined for latitudinal zones and
regions of cyclogenesis. Statistically significant trends are
found throughout the northern hemisphere and in the southern
hemisphere tropics, though the trends vary by season. Opposite
trends were observed at the two levels in some regions. No
significant differences in cyclone frequencies were found when
El Nino and La Nina years were compared. Cyclone frequencies in
North America and Europe are poorly correlated with the North
Atlantic Oscillation.
KP: NORTH-ATLANTIC OSCILLATION, CLIMATOLOGY, HEMISPHERE,
ANTICYCLONES, JANUARY, AMERICA
(36) TI: On the mechanism of North Atlantic decadal variability
AU: Selten,FM, Haarsma,RJ, Opsteegh,JD
NA: ROYAL NETHERLANDS METEOROL INST,POB 201,NL-3730 AE DE
BILT,NETHERLANDS
JN: JOURNAL OF CLIMATE, 1999, Vol.12, No.7, pp.1956-1973
IS: 0894-8755
DT: Article
AB: North Atlantic decadal climate variability is studied with a
coupled atmosphere-ocean-sea ice model (ECBILT). After having
reached an approximate statistical equilibrium in coupled mode
without applying flux corrections, a subsequent 1000-yr
integration is performed and analyzed. Compared to the current
climate, the surface temperatures are 2 degrees C warmer in the
Tropics to almost 8 degrees C warmer in the polar regions.
The covariability between the atmosphere and ocean is explored
by performing a singular value decomposition (SVD) of boreal
winter SST anomalies and 800-hPa geopotential height anomalies.
The first SVD pair shows a red variance spectrum in SST and a
white spectrum in 800-hPa height. The second mode shows a peak
in both spectra at a timescale of about 16-18 yr. The
geopotential height pattern is the model's equivalent of the
North Atlantic oscillation (NAO) pattern; the SST anomaly
pattern it; a north-south oriented dipole.
Additional experiments have revealed that the decadal
oscillation in ECBILT is basically an oscillation in the
subsurface of the ocean. The oscillation is excited by
anomalies in the atmospheric NAO pattern, both through
anomalous surface heat fluxes and anomalous El;man transports.
The atmospheric response to the SST anomaly enhances the
oscillation and slightly modifies it, but is not essential. The
atmospheric response consists primarily of a local surface air
temperature adjustment to the SST anomaly. An important element
in the physical mechanism of the oscillation is the geostrophic
response of the ocean circulation to the forced temperature
anomalies creating surface salinity anomalies through anomalous
horizontal advection. These salinity anomalies influence the
convective activity in the area of the temperature anomaly such
as to break down the subsurface temperature anomaly. Both
temperature and salinity anomalies slowly propagate eastward at
a rate consistent with the mean current.
KP: SEA-SURFACE TEMPERATURE, OCEAN-ATMOSPHERE MODEL, THERMOHALINE
CIRCULATION, INTERDECADAL VARIATIONS, SST VARIABILITY, CLIMATE-
SYSTEM, FLOW REGIMES, OSCILLATION, WINTER, PREDICTABILITY
(37) TI: Climatic variability, plant phenology, and northern ungulates
AU: Post,E, Stenseth,NC
NA: UNIV OSLO,DEPT BIOL,DIV ZOOL,POB 1050 BLINDERN,N-0316
OSLO,NORWAY
JN: ECOLOGY, 1999, Vol.80, No.4, pp.1322-1339
IS: 0012-9658
DT: Article
AB: Models of climate change predict that global temperatures and
precipitation will increase within the next century, with the
most pronounced changes occurring in northern latitudes and
during winter. A large-scale atmospheric phenomenon, the North
Atlantic Oscillation (NAO), is a strong determinant of both
interannual variation and decadal trends in temperatures and
precipitation during winter in northern latitudes, and its
recent persistence in one extreme phase may be a substantial
component of increases in global temperatures. Hence, we
investigated the influences of large-scale climatic variability
on plant phenology and ungulate population ecology by
incorporating the NAO in statistical analyses of previously
published data on: (1) the timing of flowering by plants in
Norway, and (2) phenotypic and demographic variation in
populations of northern ungulates. We analyzed 137 time series
on plant phenology for 13 species of plants in Norway spanning
up to 50 yr (44 +/- 0.5 yr, mean +/- 1 se) and 39 time series
on phenotypic and demographic traits of 7 species of northern
ungulates from 16 populations in North America and northern
Europe spanning up to 30 yr(18 +/- 2.0 yr).
Plant phenology was significantly related to the NAO in 97 time
series (71% of the total), in which dynamics of the NAO
explained, on average, between 9% and 28% of the interannual
variation in flowering dates. Following increasingly warm, wet
winters, most plant species (9 of 13 species) bloomed earlier
by an average of 13.0 +/- 0.8 d to 26.4 +/- 1.8 d. (mean +/- 1
se), one-third (4 of 11 species) bloomed longer by 13.4 +/- 1.1
d to 18.8 +/- 1.7 d, and there was an increase in spatial
variability in timing of flowering across landscapes by five of
six species. Woody plants displayed less sensitivity to
climatic variability than did herbaceous species, and early-
blooming plants were more strongly influenced by the NAO than
were late-blooming plants.
Ungulate phenotypic and demographic variables were
significantly related to the NAO in 28 time series (72% of the
total). Large-scale climatic variability influenced growth,
development, fecundity, and demographic trends of all seven
species of ungulates studied, and in some populations, the NAO
acted together with density dependence. Individuals within
mainland populations responded to winter warming with reduced
body size and increased fecundity, whereas winter warming in
maritime regions led to increased body size but reduced
fecundity. Across sex and age classes, between 43% and 70% of
the observed range in body mass among years was attributable to
the dynamics of the NAG, and within cohorts of female red deer
and reindeer, 47-70% of the observed range in fecundity was
related to the NAO during the winter preceding cohort birth
years. All but two populations of northern ungulates declined
following increasingly warmer winters, and the NAO operated, in
most instances, in concert with direct density dependence to
limit populations. In comparison to the original analyses of
these ungulate time series, in 10 of 19 series the NAO
explained an equal or greater percentage of variation than that
explained by local weather. These observations indicate that
large-scale climatic variability has a detectable influence on
the ecology of plants and animals in a variety of terrestrial
ecosystems, and that the responses of plants to winter warming
may, surprisingly, be more subtle than the responses of large
herbivores.
KP: WHITE-TAILED DEER, NORWEGIAN RED DEER, POPULATION-DYNAMICS,
REPRODUCTIVE SUCCESS, ATLANTIC OSCILLATION, BODY-WEIGHT,
ENVIRONMENTAL-CHANGE, FLOWERING PHENOLOGY, CASSIOPE-TETRAGONA,
DENSITY-DEPENDENCE
WA: climate change, density dependence, ecosystem function,
flowering dates, herbivores, large, North Atlantic Oscillation
(NAO), plant-herbivore interactions, plans phenology,
population dynamics, ungulates
(38) TI: Can environmental fluctuation prevent competitive exclusion in
sympatric flycatchers?
AU: Saetre,GP, Post,E, Kral,M
NA: UPPSALA UNIV,EVOLUTIONARY BIOL CTR,DEPT EVOLUTIONARY
BIOL,NORBYVAGEN 18D,S-75236 UPPSALA,SWEDEN
UNIV OSLO,DEPT BIOL,DIV ZOOL,N-0316 OSLO,NORWAY
FORESTRY COMMISS,DLOUHA VES 78386,CZECH REPUBLIC
JN: PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL
SCIENCES, 1999, Vol.266, No.1425, pp.1247-1251
IS: 0962-8452
DT: Article
AB: Ecology has been characterized by a central controversy for
decades: namely, whether the distribution and abundance of
organisms are determined by species interactions, such as
competitive exclusion, or by environmental conditions. In part,
this is because competitive exclusion has not been convincingly
demonstrated in open, natural systems. In addition, traditional
theoretical models cannot predict the outcome of competitive
Interactions in the presence of environmental variability. In
this paper we document the limiting influence of strong
interspecific competition on population dynamics and nestling
mortality in a mixed population of pied flycatchers (Ficedula
hypoleuca) and collared flycatchers (F. albicollis) in a narrow
zone of sympatry. Whereas the former species was limited mainly
by interspecific competition, the latter species was limited by
the concerted influences of intraspecific competition and
climate. The analysis suggests a march towards competitive
exclusion of the pied flycatcher during warm periods. However,
competitive exclusion is apparently prohibited on a local scale
because intraspecific competition among individual collared
flycatchers intensifies when they are forced to cope with
severe environmental conditions, promoting the temporary and
local presence of pied flycatchers.
KP: VARIABLE ENVIRONMENTS, CLIMATE
WA: Ficedula albicollis, Ficedula hypoleuca, interspecific
competition, intraspecific competition, population dynamics,
North Atlantic Oscillation
(39) TI: Multiple weather regimes in the summertime North Atlantic
circulation
AU: Mukougawa,H, Sato,H
NA: HOKKAIDO UNIV,GRAD SCH ENVIRONM EARTH SCI,10 KITA,5
NISHI,SAPPORO,HOKKAIDO 060081,JAPAN
JN: JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN, 1999, Vol.77,
No.2, pp.483-494
IS: 0026-1165
DT: Article
AB: Summertime weather regimes are examined over the North Atlantic
sector based on a 44-year series of daily 700 hPa height
anomalies for the period 1951-1994 in order to deepen our
understandings of weather regime dynamics in the real
atmosphere. Weather regimes are identified by examining the
probability density function (PDF) in three-dimensional phase
space, which is spanned by the three leading empirical
orthogonal functions (EOFs) of the anomaly fields.
Five weather regimes are obtained. Each weather regime
corresponds to a distinct region with statistically significant
large PDF values compared with multivariate Gaussianity. These
include two extreme phases of the North Atlantic Oscillation
(NAO), and flow patterns with intensified jet streams over the
North Atlantic.
The characteristics of weather regimes in summer are described
in comparison with those in winter. The similarity in the
circulation pattern of weather regimes in both seasons suggests
the robustness of summertime weather regimes against the
seasonal cycle. We discuss the persistence and transition of
summertime weather regimes in connection with the bifurcation
property of weather regimes elucidated in simple atmospheric
models. The interannual variation of the occurrence frequency
of weather regimes is also discussed.
KP: LOW-FREQUENCY VARIABILITY, FLOW REGIMES, WINTERTIME CIRCULATION,
PERSISTENT ANOMALIES, HEMISPHERE WINTER, BLOCKING, MODEL,
TRANSITION, MOTIONS
(40) TI: Variability of the Eurasian pattern and its interpretation by
wave activity flux
AU: Ohhashi,Y, Yamazaki,K
NA: HOKKAIDO UNIV,GRAD SCH ENVIRONM EARTH SCI,10 KITA,5
NISHI,SAPPORO,HOKKAIDO 060081,JAPAN
JN: JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN, 1999, Vol.77,
No.2, pp.495-511
IS: 0026-1165
DT: Article
AB: In this study, recent variability of the Eurasian (EU) pattern
during 1978-94 and its association with wave activity flux are
investigated. The sign of the wintertime EU index abruptly
reversed from positive to negative in winter 1988/89,
concurrent with the intensified polar vortex. To investigate
the mechanism of the EU pattern in detail, we computed the wave
activity flux. When the EU index is positive, the Rossby wave
propagation appears from North Europe to East Asia directly.
When the EU index is negative the wave activity flux is
directed more southeastward to the Middle East.
An empirical orthogonal function (EOF) analysis is performed
for the wave activity flux to clarify the variations of the
Rossby wave propagation over Eurasia. Two dominant modes
associated with the EU pattern were detected. The first mode is
closely linked with the height anomaly over arctic regions and
contributes to a shift in the 1988/89 winter atmosphere. The
second mode is related to the other principal teleconnection
patterns: the North Atlantic Oscillation (NAO), and
Pacific/North American (PNA) patterns.
The appearance of the modes are interpreted in terms of wave
forcing to the zonal wind, and the meridional wave propagation
of Rossby waves. The Rossby wave with wavenumber three, plays
an important role in the zonal wind changes of the first mode.
The meridional profile of the zonal wind is consistent with the
structure of wave activity flux. The positive feedback between
the wave activity and the zonal wind is responsible for the
dominance of the first EU mode.
KP: NORTHERN HEMISPHERE WINTER, GEOPOTENTIAL HEIGHT FIELD,
INTERANNUAL VARIABILITY, TELECONNECTION PATTERNS, CIRCULATION,
ATMOSPHERE, TEMPERATURES, OSCILLATION, PACIFIC
(41) TI: A hemispheric-scale quasi-decadal oscillation and its signature
in Northern Japan
AU: Xie,SP, Noguchi,H, Matsumura,S
NA: HOKKAIDO UNIV,GRAD SCH ENVIRONM EARTH SCI,10 KITA,5
NISHI,SAPPORO,HOKKAIDO 060081,JAPAN
NATL RES INST EARTH SCI & DISASTER PREVENT,TSUKUBA,IBARAKI
305,JAPAN
JN: JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN, 1999, Vol.77,
No.2, pp.573-582
IS: 0026-1165
DT: Article
AB: Pronounced quasi-decadal oscillation in surface air temperature
over northern Japan is linked to the North Atlantic Oscillation
(NAG). A NAG-based regression analysis reveals a hemispheric-
scale decadal temperature anomaly pattern that features a
seesaw between eastern Canada/Greenland and northern Eurasia at
high latitudes, with additional centers of action in the
eastern United States and North Africa/Middle East. Advection
of climatological mean temperature gradient by anomalous winds
seems to be a mechanism for these temperature anomalies.
Particularly, positive temperature anomalies over Siberia at
NAO's positive phase are associated with anomalous
southwesterly winds on the upstream side. The advection by mean
westerlies is also important over Eurasia, bringing large
decadal variability to northern Japan. This quasi-decadal
oscillation can be traced farther eastward to the North
Pacific, in the Aleutian low and in sea surface temperature on
the subarctic Gent. A possible inter-oceanic link between the
North Atlantic and Pacific is discussed.
KP: SEA-SURFACE TEMPERATURE, ATLANTIC OSCILLATION, PACIFIC,
CIRCULATION, WINTER, OCEAN, VARIABILITY
(42) TI: Variability of the simulated meridional heat transport in the
North Atlantic for the period 1951-1993
AU: Hakkinen,S
NA: NASA,GODDARD SPACE FLIGHT CTR,CODE 971,GREENBELT,MD,20771
JN: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1999, Vol.104, No.C5,
pp.10991-11007
IS: 0148-0227
DT: Article
AB: A 43-year ocean model simulation for the period 1951-1993 is
analyzed, with a focus on the meridional heat transport (MHT)
as a proxy for the strength of meridional overturning cell
(MOC) at 25 degrees N. The surface heat flux forcing associated
with the North Atlantic Oscillation (NAO) pattern is related to
the variability in MHT both on interannual and longer
timescales. The manifestation of the interannual and decadal
oceanic response to NAO is nonlocal, as evidenced by the
concentrated heat content and sea level variability at the Gulf
Stream and North Atlantic Current regions and shown by the
comparison of the model sea level variability to the altimeter
data between low MHT years in mid-1980s and high MHT years in
early 1990s. The same area is singled out by empirical
orthogonal function analysis in the leading mode of the sea
level. MHT and time series of the leading sea level mode are
highly correlated, which reflects the importance of the MOC in
determining the variability of the heat content of the whole
basin. Also, the model suggests that the MHT/MOC has entered a
very strong phase since the mid-1980s and this trend has
continued up to the end of 1993; this behavior follows the
general trend in the NAO index.
KP: SEA-SURFACE TEMPERATURE, INTERPENTADAL VARIABILITY, OCEAN,
CIRCULATION, MODEL, CLIMATE, WINTER, ICE, ANOMALIES, WATERS
(43) TI: UK wheat quality and economic value are dependent on the North
Atlantic oscillation
[Full text delivery]
AU: Kettlewell,PS, Sothern,RB, Koukkari,WL
NA: HARPER ADAMS UNIV COLL,CROP & ENVIRONM RES CTR,NEWPORT TF10
8NB,SHROPS,ENGLAND
UNIV MINNESOTA,DEPT PLANT BIOL,COLL BIOL SCI,ST PAUL,MN,55108
JN: JOURNAL OF CEREAL SCIENCE, 1999, Vol.29, No.3, pp.205-209
IS: 0733-5210
DT: Article
KP: SEA-SURFACE TEMPERATURE, CLIMATE
WA: Hagberg falling number, specific weight, sea surface
temperature, NAO
(44) TI: Simulation of recent northern winter climate trends by
greenhouse-gas forcing
AU: Shindell,DT, Miller,RL, Schmidt,GA, Pandolfo,L
NA: NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY,10025
COLUMBIA UNIV,CTR CLIMATE SYST RES,NEW YORK,NY,10025
COLUMBIA UNIV,DEPT APPL PHYS,NEW YORK,NY,10027
UNIV BRITISH COLUMBIA,DEPT EARTH & OCEAN SCI,VANCOUVER,BC V6T
1Z4,CANADA
JN: NATURE, 1999, Vol.399, No.6735, pp.452-455
IS: 0028-0836
DT: Article
AB: The temperature of air at the Earth's surface has risen during
the past century(1), but the fraction of the warming that can
be attributed to anthropogenic greenhouse gases remains
controversial. The strongest warming bends have been over
Northern Hemisphere land masses during winter, and are closely
related to changes in atmospheric circulation. These
circulation changes are manifested by a gradual reduction in
high-latitude sea-level pressure, and an increase in mid-
latitude sea-level pressure associated with one phase of the
Arctic Oscillation (a hemisphere-scale version of the North
Atlantic Oscillation)(2). Here we use several different
climate-model versions to demonstrate that the observed sea-
level-pressure trends, including their magnitude, can be
simulated by realistic increases in greenhouse-gas
concentrations, Thus, although the warming appears through a
naturally occurring mode of atmospheric variability, it may be
anthropogenically induced and may continue to rise. The Arctic
Oscillation trend is captured only in climate models that
include a realistic representation of the stratosphere, while
changes in ozone concentrations are not necessary to simulate
the observed climate trends. The proper representation of
stratospheric dynamics appears to be important to the
attribution of climate change, at least on a broad regional
scale.
KP: SURFACE AIR-TEMPERATURE, STRATOSPHERIC CIRCULATION, INTERANNUAL
VARIABILITY, GEOPOTENTIAL HEIGHT, MIDDLE ATMOSPHERE, HEMISPHERE,
MODEL, OZONE, TROPOSPHERE, GCM
(45) TI: Precipitation at Armagh Observatory 1838-1997
AU: Butler,CJ, Coughlin,ADS, Fee,DT
NA: ARMAGH OBSERV,COLL HILL,ARMAGH BT61 9G,NORTH IRELAND
JN: BIOLOGY AND ENVIRONMENT-PROCEEDINGS OF THE ROYAL IRISH ACADEMY,
1998, Vol.98B, No.2, pp.123-140
IS: 0791-7945
DT: Article
AB: The meteorological series maintained at Armagh Observatory
began in 1795 and are the longest in Ireland and among the
longest in the British Isles. Here we present the monthly mean
daily precipitation recorded at Armagh since 1838. Variations
in the distribution of the rainfall during the year, over this
period, are apparent, with a tendency for drier summers in
recent decades. We find a significant correlation between the
mean seasonal rainfall and the North Atlantic Oscillation index
during autumn and winter, and there appears to be a negative
correlation between the summer rainfall and the North Atlantic
Oscillation index for the previous winter. A search for
periodicities has been made and Ilo evidence of an eleven-year
cycle similar to the Sunspot cycle has been found. However,
Fourier analysis reveals an approximate seven-year cycle in
summer rainfall. We examine the evidence that this cycle may be
linked either to the Taurid meteor stream or to the North
Atlantic Oscillation.
KP: IRISH
(46) TI: A proposed mechanism for the Bohuslan herring periods
[Full text delivery]
AU: Corten,A
NA: NETHERLANDS INST FISHERIES RES,RIVO DLO,POB 68,NL-1970 AB
IJMUIDEN,NETHERLANDS
JN: ICES JOURNAL OF MARINE SCIENCE, 1999, Vol.56, No.2, pp.207-220
IS: 1054-3139
DT: Article
AB: During the last 500 years large numbers of herring have
occasionally appeared in winter along the Swedish Skagerrak
coast. These ''Bohuslan'' herring periods, sometimes lasting
for several decades, were probably caused by a temporary shift
of the over-wintering grounds of North Sea herring. In normal
years North Sea herring over-winter in the adjacent waters of
the northeastern North Sea. As yet there is no commonly
accepted explanation for the occasional shifts of the over-
wintering grounds towards the Skagerrak.
The environmental cause of the Bohuslan herring periods was
investigated by looking at the most recent episode of herring
invasions in the Skagerrak. In the winters of 1962-1965 large
numbers of North Sea herring again entered the Skagerrak and
these invasions showed many features of the old Bohuslan
herring periods. The only anomalous environmental parameter at
this time was a high Frequency of easterly winds in the autumns
of 1962 and 1963. It is assumed that these easterly winds
forced surface water out of the Skagerrak and thereby
strengthened the subsurface Norwegian french Current that flows
into the Skagerrak. This current could easily transport herring
from the normal over-wintering area near Egersund Bank towards
the Skagerrak. It is shown that former Bohuslan or Skagerrak
herring periods started in years when the North Atlantic
Oscillation was in a negative phase and when easterly winds
must have dominated in autumn too.
Bohuslan herring periods were more persistent than the periods
of easterly winds. The persistence of the herring migrations is
explained by ''site-fidelity'' of the older herring. Once a new
migration has been adopted by the population it is repeated in
subsequent years even when the original environmental cause has
disappeared. An existing migration pattern can be changed only
by a new, strong year class, that has not yet developed an
attachment to the traditional over-wintering area. It is shown
that the two most recent episodes of Skagerrak invasions were
indeed initiated by strong recruiting year classes. (C) 1999
International Council for the Exploration of the Sea.
KP: NORTH-ATLANTIC OSCILLATION
WA: herring, North Sea, Skagerrak, Bohuslan periods, North Atlantic
Oscillation
(47) TI: Temporal variability of the seasonal sea-level cycle in the
North Sea and Baltic Sea in relation to climate variability
AU: Plag,HP, Tsimplis,MN
NA: NORWEGIAN MAPPING AUTHOR,GEODET INST,N-3500 HONEFOSS,NORWAY
CHRISTIAN ALBRECHTS UNIV KIEL,INST GEOPHYS,D-24118 KIEL,GERMANY
PROUDMAN OCEANOG LAB,BIDSTON,ENGLAND
JN: GLOBAL AND PLANETARY CHANGE, 1999, Vol.20, No.2-3, pp.173-203
IS: 0921-8181
DT: Article
AB: Based on monthly mean sea-level and meteorological data from
the North Sea and Baltic Sea areas, the temporal variability of
the annual and semiannual constituents in sea level and
meteorological parameters is investigated on decadal time
scales, A significant regionally coherent temporal variability
of the annual and semiannual constituents in sea level, air
pressure, air temperature and the wind field is established.
The decadal variability of the annual and semiannual
constituents in sea level is found to be closely correlated
with the variability in the mechanical atmospheric forcing.
This indicates a non-steric contribution to the long-period
variations of the seasonal cycle in coastal sea level. In all
parameters considered, the largest changes compared to earlier
times occurred in the last two decades. The variation found in
air pressure indicates an increase of the difference between
maritime and continental climate regions in Northern Europe.
These variations may be linked to variations of the North
Atlantic Oscillation on decadal time scales as well as a
general warming trend. (C) 1999 Elsevier Science B.V. All
rights reserved.
KP: SURFACE WIND STRESS, POLE TIDE, ATLANTIC OSCILLATION, SOUTHERN
OSCILLATION, DRAG COEFFICIENT, NUMERICAL-MODEL, HEAT-FLUX,
OCEAN, TEMPERATURES, SURGE
WA: sea-level, seasonal cycle, North Sea, decadal variability,
climate variability
(48) TI: Surface and 700 hPa atmospheric circulation patterns for the
Great Lakes basin and eastern North America and relationship to
atmospheric teleconnections
AU: Rohli,RV, Vega,AJ, Binkley,MR, Britton,SD, Heckman,HE,
Jenkins,JM, Ono,Y, Sheeler,DE
NA: KENT STATE UNIV,DEPT GEOG,WATER RESOURCES RES
INST,KENT,OH,44242
CLARION UNIV PENNSYLVANIA,DEPT ANTHROPOL GEOG & EARTH
SCI,CLARION,PA,16214
JN: JOURNAL OF GREAT LAKES RESEARCH, 1999, Vol.25, No.1, pp.45-60
IS: 0380-1330
DT: Article
AB: Many studies have identified continental-scale atmospheric
circulation regimes, and some have been employed for various
regions, but none have involved a regional categorization of
circulation around the Great Lakes basin. Such an analysis is
important not only because of the economic and recreational
importance of the lakes, but in an effort to relate the
regional circulation types to the broader-scale modes of
atmospheric circulation, such as that forced by Fl Nino (ENSO).
In this study, rotated principal components analysis (RPCA) is
performed on the monthly mean sea-level pressure field around
the Great Lakes basin, and in a separate analysis, on the mean
700 hPa field in eastern North America. An average-linkage
clustering algorithm is applied to the RPCA scores to classify
the monthly surface circulation in the Great Lakes region and
the 700 hPa circulation over eastern North America. The
classification is used to determine whether the various
categories of regional circulation patterns are coincident with
distinct hemispheric-scale flow regimes. To do this, indices of
the modes of variability in some of the most well-known
atmospheric teleconnections during months that fall within each
circulation mode are subjected to ANOVA tests by cluster.
Results suggest that the regional atmosphere over the Great
Lakes basin undergoes long-term shifts in preferred modes of
circulation. Furthermore, flow variability associated with the
700 hPa North Atlantic Oscillation (NAO) and Pacific/North
American (PNA) teleconnections are more strongly tied to
variability in both the Great Lakes regional surface
circulation and the 700 mb eastern North American flow regimes
than is the ENSO-forced Southern Oscillation.
KP: NINO SOUTHERN OSCILLATION, PRINCIPAL COMPONENT ANALYSIS,
GEOPOTENTIAL HEIGHT FIELD, UNITED-STATES CLIMATE, SYNOPTIC
CLIMATOLOGY, HEMISPHERE WINTER, ATLANTIC OSCILLATION,
CLASSIFICATION, TEMPERATURE, ASSOCIATIONS
WA: synoptic climatology, atmospheric circulation, Great Lakes
basin
(49) TI: Spatiotemporal patterns of decadal variability in sea surface
temperature, wind speed, and sea level pressure in the North
Atlantic
LA: Russian
AU: Efimov,VV, Prusov,AV, Shokurov,MV
NA: NATL ACAD SCI UKRAINE,INST MARINE HYDROPHYS,UL KAPITANSKAYA
2,UA-335000 SEVASTOPOL,CRIMEA,UKRAINE
JN: IZVESTIYA AKADEMII NAUK FIZIKA ATMOSFERY I OKEANA, 1999,
Vol.35, No.1, pp.107-121
IS: 0002-3515
DT: Article
AB: Spatiotemporal patterns of decadal variability in sea surface
temperature, atmospheric pressure, and surface wind speed are
obtained from the GOADS dataset by the cluster analysis
technique. Sequences of typical structures and their coupling
over the last 42 years are examined. On decadal time scales,
the pressure and wind anomaly fields are found to roughly
satisfy the geostrophic balance. A mode associated with the
well-known North Atlantic Oscillation is identified in these
fields. Other modes of decadal variability-the tropical dipole,
the subtropical-gyre mode, and the thermohaline mode in the
high-latitude North Atlantic-are found in SST anomalies. The
global dipole SST mode for the entire Atlantic Ocean is
interpreted from the standpoint of the variability in the
intensity of the Atlantic branch of the global interoceanic
thermohaline circulation (the conveyer belt). A difference in
this coupling for the Atlantic and Pacific oceans is noted.
KP: OCEAN-ATMOSPHERE MODEL, GENERAL-CIRCULATION MODEL, TROPICAL
ATLANTIC, INTERPENTADAL VARIABILITY, THERMOHALINE CIRCULATION,
INTERANNUAL VARIABILITY, INTERDECADAL VARIATIONS, ANOMALIES,
SALINITY, FLUCTUATIONS
(50) TI: Dependence of winter precipitation over Portugal on NAO and
baroclinic wave activity
AU: Ulbrich,U, Christoph,M, Pinto,JG, CorteReal,J
NA: UNIV COLOGNE,INST GEOPHYS & METEOROL,D-50923 COLOGNE,GERMANY
MAX PLANCK INST METEOROL,D-20146 HAMBURG,GERMANY
ICAT,CAMPUS FAC CIENCIAS,P-1700 LISBON,PORTUGAL
JN: INTERNATIONAL JOURNAL OF CLIMATOLOGY, 1999, Vol.19, No.4,
pp.379-390
IS: 0899-8418
DT: Article
AB: The relationship between winter (DJF) rainfall over Portugal
and the variable large scale circulation is addressed. It is
shown that the poles of the sea level pressure (SLP) field
variability associated with rainfall variability are shifted
about 15 degrees northward with respect to those used in
standard definitions of the North Atlantic Oscillation (NAO).
It is suggested that the influence of NAO on rainfall
dominantly arises from the associated advection of humidity
from the Atlantic Ocean, Rainfall is also related to different
aspects of baroclinic wave activity, the variability of the
latter quantity in turn being largely dependent on the NAG.
A negative NAO index (leading to increased westerly surface
geostrophic winds into Portugal) is associated with an
increased number of deep (p(s)<980 hPa) surface lows over the
central North Atlantic and of intermediate (980 50 degrees N) Europe, the eastern United States,
northern Africa, and the Mediterranean, while below-normal
precipitation occurs in southern Europe, eastern Canada, and
western Greenland.
Wet and dry months of one standard deviation occur at
probabilities close to those of a normal distribution in
midlatitudes. Ln the subtropics, the mean interval between two
extreme events is longer. The monthly wet and dry events seldom
(probability < 5%) last longer than 2 months. ENSO is the
single largest cause of global extreme precipitation events;
Consistent with the upward trend in global precipitation,
globally, the averaged mean interval between two dry months
increased by similar to 28% from 1900-44 to 1945-88. The
percentage of wet areas over the United States has more than
doubled (from similar to 12% to > 24%) since the 1970s, while
the percentage of dry areas has decreased by a similar amount
since the 1940s. Severe droughts and floods comparable to the
1988 drought and 1993 flood in the Midwest have occurred 2-9
times in each of several other regions of the world during this
century.
KP: UNITED-STATES, SOUTHERN OSCILLATION, GEOPOTENTIAL HEIGHT,
CLIMATE VARIATIONS, GAUGE OBSERVATIONS, AIR-TEMPERATURE, NORTH-
AMERICA, 1988 DROUGHT, EL-NINO, TRENDS
(124) TI: Extension to the North Atlantic Oscillation using early
instrumental pressure observations from Gibraltar and south-
west Iceland
AU: Jones,PD, Jonsson,T, Wheeler,D
NA: UNIV E ANGLIA,CLIMAT RES UNIT,NORWICH NR4 7TJ,NORFOLK,ENGLAND
ICELAND METEOROL OFF,IS-150 REYKJAVIK,ICELAND
UNIV SUNDERLAND,DEPT GEOG,SUNDERLAND SR1 3SD,DURHAM,ENGLAND
JN: INTERNATIONAL JOURNAL OF CLIMATOLOGY, 1997, Vol.17, No.13,
pp.1433-1450
IS: 0899-8418
DT: Article
AB: Early instrumental pressure measurements from Gibraltar and the
Reykjavik area of Iceland have been used to extend to 1821 the
homogeneous pressure series at the two locations. In winter the
two sites are located close to the centres of action that
comprise the North Atlantic Oscillation (NAG). The extended
'winter half-year' record of the NAO enables recent changes in
the record to be placed in the context of the period 1823-1996.
The period since the early 1970s is the most prolonged positive
phase of the oscillation and the late 1980s and early 1990s is
the period with the highest values (strongest westerlies). The
winter of 1995-1996 marked a dramatic switch in the index, with
the change from 1994-1995 being the greatest change recorded
from one year to the next since the series began in 1823. (The
extended Gibraltar and Reykjavik monthly pressures and the NAO
series can be found on the Climatic Research Unit home page,
http://www.cru.uea.ac.uk/.). (C) 1997 by the Royal
Meteorological Society.
KP: HEMISPHERE, TELECONNECTIONS, TEMPERATURES, WINTER, EUROPE
WA: North Atlantic Oscillation, Gibraltar, Iceland, pressure data
(125) TI: Aspects of climate variability in the North Atlantic sector:
Discussion and relation to the Greenland Ice Sheet Project 2
high-resolution isotopic signal
AU: Barlow,LK, Rogers,JC, Serreze,MC, Barry,RG
NA: UNIV COLORADO,INST ARCTIC & ALPINE RES,CAMPUS BOX
450,BOULDER,CO,80309
UNIV COLORADO,COOPERAT INST RES ENVIRONM SCI,DIV CRYOSPHER &
POLAR PROC,BOULDER,CO,80309
OHIO STATE UNIV,DEPT GEOG,COLUMBUS,OH,43210
OHIO STATE UNIV,BYRD POLAR RES CTR,COLUMBUS,OH,43210
JN: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1997, Vol.102, No.C12,
pp.26333-26344
DT: Article
AB: This paper reviews aspects of climate variability in the North
Atlantic sector that may influence the seasonal to decadal
scale isotopic signal in the Greenland Ice Sheet Project 2
(GISP2) ice core. Interpretation of the isotopic signal and its
spatial applicability at the seasonal level requires
investigation into synoptic scale climatology. We discuss
possible climatic influences of (1) likely source regions of
precipitation reaching the GISP2 site, (2) the characteristics
of cyclone activity over the North Atlantic sector, and (3)
changes in major atmospheric features such as the mean sea
level Icelandic Low and Azores High pressure systems, the North
Atlantic Oscillation, and the Baffin trough. Next, we evaluate
correlations between the GISP2 deuterium isotopic signal and
coastal temperatures with atmospheric pressure patterns,
thereby deriving climatic interpretations of the high-
resolution isotopic record. The GISP2 site is influenced by
both the Icelandic Low to the southeast and Davis Strait/Baffin
Bay storms to the southwest and west. The North Atlantic
Oscillation influences the GISP2 isotopic signal through the
seesaw in winter temperatures between west Greenland and
northern Europe. Agreement in excursion directions of GISP2
isotopes and east Greenland and Iceland temperature records is
associated with different positions of the Baffin trough in
winter and also with anomalous 500-mbar net geostrophic flow.
Linkages between isotopic excursion direction and atmospheric
variability need to be explored further by comparison with
additional seasonal data sets from other Greenland ice cores.
KP: SEA-LEVEL PRESSURE, TEMPERATURE TRENDS, PRECIPITATION,
OSCILLATION, HEMISPHERE, FREQUENCY, CORE
(126) TI: The climate signal in the stable isotopes of snow from Summit,
Greenland: Results of comparisons with modern climate
observations
AU: White,JWC, Barlow,LK, Fisher,D, Grootes,P, Jouzel,J, Johnsen,SJ,
Stuiver,M, Clausen,H
NA: UNIV COLORADO,INST ARCTIC & ALPINE RES,BOULDER,CO,80309
UNIV COPENHAGEN,DEPT GEOPHYS,DK-2100 COPENHAGEN,DENMARK
GEOL SURVEY CANADA,TERRAIN SCI DIV,GLACIOL SECT,OTTAWA,ON K1A
0E8,CANADA
CHRISTIAN ALBRECHTS UNIV KIEL,LEIBNIZ LAB,D-24118 KIEL,GERMANY
CTR ETUD SACLAY,LAB MODELISAT CLIMAT & ENVIRONM,F-91191 GIF SUR
YVETTE,FRANCE
UNIV WASHINGTON,DEPT GEOL SCI,SEATTLE,WA,98195
UNIV WASHINGTON,QUATERNARY RES CTR,SEATTLE,WA,98195
UNIV REYKJAVIK,INST SCI,REYKJAVIK,ICELAND
UNIV COLORADO,DEPT GEOL SCI,BOULDER,CO,80309
JN: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1997, Vol.102, No.C12,
pp.26425-26439
DT: Article
AB: Recent efforts to link the isotopic composition of snow in
Greenland with meteorological and climatic parameters have
indicated that relatively local information such as observed
annual temperatures from coastal Greenland sites, as well as
more synoptic scale features such as the North Atlantic
Oscillation (NAG) and the temperature seesaw between
Jakobshaven, Greenland, and Oslo, Norway, are significantly
correlated with delta(18)O and delta D values from the past few
hundred years measured in ice cores. In this study we review
those efforts and then use a new record of isotope values from
the Greenland Ice Sheet Project 2 and Greenland Ice Core
Project sites at Summit, Greenland, to compare with
meteorological and climatic parameters. This new record
consists of six individual annually resolved isotopic records
which have been average to produce a Summit stacked isotope
record. The stacked record is significantly correlated with
local Greenland temperatures over the past century (r = 0.471),
as well as a number of other records including temperatures and
pressures from specific locations as well as temperature and
pressure patterns such as the temperature seesaw and the North
Atlantic Oscillation. A multiple linear regression of the
stacked isotope record with a number of meteorological and
climatic parameters in the North Atlantic region reveals that
five variables contribute significantly to the variance in the
isotope record: winter NAG, solar irradiance (as recorded by
sunspot numbers), average Greenland coastal temperature, sea
surface temperature in the moisture source region for Summit
(30 degrees-20 degrees N), and the annual temperature seesaw
between Jakobshaven and Oslo. Combined, these variables yield a
correlation coefficient of r = 0.71, explaining half of the
variance in the stacked isotope record.
KP: NORTH-ATLANTIC OSCILLATION, SOUTHERN OSCILLATION, WINTER
TEMPERATURES, RECORD, GISP2, SEESAW, EUROPE, CORE
(127) TI: Winter and summer temperatures in Berlin since 1929 and their
relationship with the North Atlantic Oscillation (NAG)
LA: German
AU: Malberg,H, Bokens,G
NA: INST METEOROL,CARL HEINRICH BECKER WEG 6-8,D-12165
BERLIN,GERMANY
JN: METEOROLOGISCHE ZEITSCHRIFT, 1997, Vol.6, No.5, pp.230-234
IS: 0941-2948
DT: Article
AB: As the investigation shows there exists a direct relationship
between the mean winter temperatures in Berlin and the
intensity of the circulation over the North Atlantic Ocean. The
correlation coefficient between winter temperatures (Dec.-Feb.)
and NAO amounts to 0.65 and 0.71 for the winter half-year
(Oct.-Mar.). Both values are significant on the 99.9 %-level.
The correlation coefficient between summer temperatures (June-
Aug.) and NAO is much weaker. The values are only 0.13 and 0.24
for the summer half-pear (Apr.-Sep.), respectively. Furthermore
a remarkable increase of the NAO occurs for winter and spring
since several decades, but no increase is observed for summer
and fall. The number of storms over the Northern Atlantic is
also significantly correlated to the NAG.
KP: FREQUENCY, TRENDS
(128) TI: On the relationships between daily circulation patterns and
precipitation in Portugal
AU: Zhang,XB, Wang,XLL, CorteReal,J
NA: ATMOSPHER ENVIRONM SERV,CLIMATE RES BRANCH,4905 DUFFERIN
ST,DOWNSVIEW,ON M3H 5T4,CANADA
UNIV LISBON,FAC SCI,DEPT PHYS,P-1700 LISBON,PORTUGAL
UNIV VICTORIA,CANADIAN CTR CLIMATE MODELING & ANAL,ATMOSPHER
ENVIRONM SERV,VICTORIA,BC V8W 2Y2,CANADA
JN: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1997, Vol.102,
No.D12, pp.13495-13507
DT: Article
AB: Daily circulation (sea level pressure) maps over east Atlantic-
Europe were classified into six circulation patterns (CPs) by
using k-means clustering coupled with principal component
analysis. The relationships between winter monthly rainfall in
Portugal and the occurrence frequencies of the CPs were also
examined. The CP classification scheme is effective not only in
discriminating regional wet/dry weather conditions, but also in
differentiating between various conditions associated with
different precipitation intensities. For southern Portugal, CP6
and CP3 are the wettest patterns: under their presence the
rainfall occurrence probability and the rainy day rainfall
intensity are twice as high as those associated with the dry
CPs; with only about 26.6% occurrence probability the two wet
CPs together contribute about 66.8% of the total rainfall. For
northern Portugal, CP6 and CP4 turned out to be the wettest
patterns. They produce over 60% of the total rainfall with only
31% chance of occurrence. In terms of long-term variation the
precipitation is also intimately related to the occurrence
frequencies of the CPs. The occurrence frequencies of CPs were
found to be good predictors for the regional precipitation. In
addition, it is evident that the decrease of March rainfall
throughout the country in the last 3 decades has been a
consequence of a reduction in the occurrence frequency of the
wettest circulation pattern, CP6, which coincides with the
upward trend of the North Atlantic Oscillation index and could
be related to the northeastward shifting and strengthening of
the Azores High.
KP: SEA-LEVEL PRESSURE, WEATHER PATTERNS, NORTH-ATLANTIC, CLIMATE-
CHANGE, REGIMES, TEMPERATURES, VARIABILITY, ANOMALIES
(129) TI: Polar motion and the North Atlantic Oscillation
AU: Zhou,YH, Zheng,DW, Chao,BF
NA: CHINESE ACAD SCI,SHANGHAI ASTRON OBSERV,SHANGHAI 200030,PEOPLES
R CHINA
JN: CHINESE SCIENCE BULLETIN, 1997, Vol.42, No.11, pp.927-931
IS: 1001-6538
DT: Article
WA: polar motion, the North Atlantic Oscillation, excitation
function, interannual time scale
(130) TI: North Atlantic storm track variability and its association to
the north Atlantic oscillation and climate variability of
northern Europe
AU: Rogers,JC
NA: OHIO STATE UNIV,DEPT GEOG,COLUMBUS,OH,43210
JN: JOURNAL OF CLIMATE, 1997, Vol.10, No.7, pp.1635-1647
IS: 0894-8755
DT: Article
AB: The primary mode of North Atlantic storm track variability is
identified using rotated principal component analysis (RPCA) on
monthly fields of root-mean-squares of daily high-pass filtered
(2-8-day periods) sea level pressures (SLP) for winters
(December-February) 1900-92. It is examined in terms of its
association with 1) monthly mean SLP fields, 2) regional low-
frequency teleconnections, and 3) the seesaw in winter
temperatures between Greenland and northern Europe. The
principal storm track component is characterized by high
synoptic variability preferring one of two areas at any given
time. The northeastern Atlantic center (identified by positive
RPCA scores) is characterized by deep cyclones in the area
extending from Iceland northeastward to the Norwegian and
Barents Seas, whereas the Bay of Biscay center (negative
scores) is linked to cyclone activity around that area and into
the Mediterranean basin. Combined principal component analysis
is used to link the high-frequency storm track pressure
variability with that of lower frequencies (monthly mean
pressures). In this, the primary storm track pattern is linked
to large monthly mean SLP variations around the Bay of Biscay
and near northern Scandinavia and the Barents Sea. This pattern
does not suggest a strong storm track link to the North
Atlantic Oscillation (NAG). Instead, the results presented
indicate that the dominant mode of variability in the storm
track is associated with low-frequency SLP anomalies in the
extreme northeastern Atlantic. When the component scores reach
their highest positive values, both the mean Atlantic subpolar
low and subtropical high are unusually strong and displaced
farther northeast than normal. The pressure field intensifies
to the northeast and produces strong zonal flow extending into
Europe, bringing abnormally high surface air temperatures as
far east as Siberia and below normal temperatures over
Greenland and northern Africa (the ''Greenland below'' seesaw
mode, GB). Besides this eastward extension of tie mean pressure
field, anomalously high European winter temperatures can also
be somewhat less frequently caused by mild return flow around
the Siberian high, which is displaced farther west than normal.
In this situation the Icelandic low is in its normal Denmark
Strait location and cyclones move along the more southerly
storm track toward the Mediterranean basin, contributing to the
synoptic forcing that helps develop the westward extended high.
The NAO appears to be only indirectly linked to the European
component of the GB mode of the winter surface ail temperature
seesaw.
KP: SEA-LEVEL PRESSURE, GEOPOTENTIAL HEIGHT, CYCLONE TRACKS,
CIRCULATION, HEMISPHERE, FREQUENCY, WINTER, TEMPERATURE,
PATTERNS, TRENDS
(131) TI: Long-term climate forcing of European herring and sardine
populations
[Full text delivery]
AU: Alheit,J, Hagen,E
NA: BALT SEA RES INST,SEESTR 15,D-18119 WARNEMUNDE,GERMANY
JN: FISHERIES OCEANOGRAPHY, 1997, Vol.6, No.2, pp.130-139
IS: 1054-6006
DT: Article
AB: Records of the herring, Clupea harengus, fishery off the
Swedish coast of Bohuslan, in the Skagerrak, date back to the
10th century. Nine periods, each lasting several decades, are
known during which large quantities of herring were caught
close to the short. In the 1895-96 season, more than 200 000
tonnes were landed. During the 'interim' periods, which
stretched over 50 or more years, the herring fishery played
little role in the economy of this region. Several other
herring fisheries in European waters overlap with recent
Bohuslan periods whereas the Norwegian spring-spawning herring
and some sardine, Sardina pilchardus, fisheries exhibit
alternating periods. A study of the climatological/hydrographic
scenario of all Bohuslan periods and those of herring in the
English Channel and the Bay of Biscay showed that, on a decadal
scale, they coincided with times when there was a strong ice
cover off Iceland, severe winters in western Europe with
extremely cold air and water temperatures, a reduction of
westerly winds as indicated by negative anomalies in the North
Atlantic Oscillation (NAO) index and a minimum of south-
westerly winds over England in response to meridional
migrations of the belt of westerly winds. Periods of the
Norwegian spring-spawning herring and sardines in the English
Channel coincided with inverse climatological/hydrographic
situations. It is concluded that climate variation governed the
alternating herring and sardine periods.
KP: TEMPERATURES, SEA, GREENLAND, FISH
WA: herring, sardine, stock fluctuations, climate variation, NAO
index
(132) TI: Variations of snow depth and duration in the Swiss Alps over
the last 50 years: Links to changes in large-scale climatic
forcings
AU: Beniston,M
NA: UNIV FRIBOURG,INST GEOG,CH-1700 FRIBOURG,SWITZERLAND
JN: CLIMATIC CHANGE, 1997, Vol.36, No.3-4, pp.281-300
IS: 0165-0009
DT: Article
AB: A study of snow statistics over the past 50 years at several
climatological stations in the Swiss Alps has highlighted
periods in which snow was either abundant or not. Periods with
relative low snow amounts and duration are closely linked to
the presence of persistent high surface pressure fields over
the Alpine region during late Fall and in Winter. These high
pressure episodes are accompanied by large positive temperature
anomalies and low precipitation, both of which are unfavorable
for snow accumulation during the Winter. The fluctuations of
seasonal to annual pressure in the Alpine region is strongly
correlated with anomalies of the North Atlantic Oscillation
index, which is a measure of the strength of the westerly Row
over the Atlantic. This implies that large-scale forcing, and
not local or regional factors, plays a dominant role in
controling the timing and amount of snow in the Alps, as
evidenced by the abundance or dearth of snow over several
consecutive years. Furthermore, since the mid-1980s, the length
of the snow season and snow amount have substantially
decreased, as a result of pressure fields over the Alps which
have been far higher and more persistent than at any other time
this century. A detailed analysis of a number of additional
Alpine stations for the last 15 years shows that the
sensitivity of the snow-pack to climatic fluctuations
diminishes above 1750 m. In the current debate on
anthropogenically-induced climatic change, this altitude is
consistent with other studies and estimates of snow-pack
sensitivity to past and projected future global warming.
KP: GENERAL-CIRCULATION MODEL, CHANGE SCENARIO, SWITZERLAND,
TEMPERATURE, SIMULATION, TRENDS, CO2
(133) TI: Decadal variations in climate associated with the north
Atlantic oscillation
AU: Hurrell,JW, VanLoon,H
NA: NATL CTR ATMOSPHER RES,BOULDER,CO,80307
JN: CLIMATIC CHANGE, 1997, Vol.36, No.3-4, pp.301-326
IS: 0165-0009
DT: Article
AB: Large changes in the wintertime atmospheric circulation have
occurred over the past two decades over the ocean basins of the
Northern Hemisphere, and these changes have had a profound
effect on regional distributions of surface temperature and
precipitation. The changes over the North Pacific have been
well documented and have contributed to increases in
temperatures across Alaska and much of western North America
and to decreases in sea surface temperatures over the central
North Pacific. The variations over the North Atlantic are
related to changes in the North Atlantic Oscillation (NAG).
Over the past 130 years, the NAO has exhibited considerable
variability at quasibiennial and quasi-decadal time scales, and
the latter have become especially pronounced the second half of
this century. Since 1980, the NAO has tended to remain in one
extreme phase and has accounted for a substantial part of the
observed wintertime surface warming over Europe and downstream
over Eurasia and cooling in the northwest Atlantic. Anomalies
in precipitation, including dry wintertime conditions over
southern Europe and the Mediterranean and wetter-than-normal
conditions over northern Europe and Scandinavia since 1980, are
also linked to the behavior of the NAG. Changes in the monthly
mean flow over the Atlantic are accompanied by a northward
shift in the storm tracks and associated synoptic eddy
activity, and these changes help to reinforce and maintain the
anomalous mean circulation in the upper troposphere. It is
important that studies of trends in local climate records, such
as those from high elevation sites, recognize the presence of
strong regional patterns of change associated with phenomena
like the NAG.
KP: SEA-LEVEL PRESSURE, GREENLAND ICE-SHEET, SURFACE-TEMPERATURE,
ATMOSPHERIC CIRCULATION, INTERDECADAL VARIABILITY, HEMISPHERE
CIRCULATION, SOUTHERN OSCILLATION, MEAN TEMPERATURE, HEAT-FLUX,
EL-NINO
(134) TI: The recent increase in North Atlantic wave heights
AU: Kushnir,Y, Cardone,VJ, Greenwood,JG, Cane,MA
NA: COLUMBIA UNIV,LAMONT DOHERTY EARTH OBSERV,ROUTE
9W,PALISADES,NY,10964
OCEANWEATHER INC,COS COB,CT
JN: JOURNAL OF CLIMATE, 1997, Vol.10, No.8, pp.2107-2113
IS: 0894-8755
DT: Article
AB: The nature and causes of the recent increase in North Atlantic
wave heights are explored by combining a numerical hindcast
with a statistical analysis. The numerical hindcast
incorporates a IO-yr history (1980-89) of North Atlantic, twice
daily wind analyses to generate a monthly averaged significant
wave height (SWH) history. The hindcast compares favorably with
published monthly averaged SWH observations. The link between
model-generated wintertime monthly SWH and monthly averaged sea
lever pressure (SLP) data is determined by means of a canonical
correlation analysis (CCA). Within the analysis domain, most of
the variance in SWH and SLP is captured by two pairs of joint
patterns. The leading pair consists of a SLP dipole resembling
the North Atlantic Oscillation (NAG) and a SWH dipole in
spatial quadrature relation to it. Using the CCA results, an
extended statistical hindcast of monthly wave fields is
generated from sea level pressure data and used to
quantitatively estimate the systematic increase in wave heights
since the 1960s. It is shown that an increasing trend in SWH at
several northeast Atlantic locations since 1960 or so is
related to the systematic deepening of the Icelandic low and
intensification of the Azores high over the last three decades.
The analysis suggests that wave height south of 40 degrees N
has decreased during the same period.
KP: SEA-SURFACE TEMPERATURE, CANONICAL CORRELATION-ANALYSIS,
OSCILLATION, WINTER, WIND, PRECIPITATION, VARIABILITY,
CIRCULATION, PATTERNS, TRENDS
(135) TI: Association of the Indian summer monsoon with the Northern
Hemisphere mid-latitude circulation
AU: Kripalani,RH, Kulkarni,A, Singh,SV
NA: INDIAN INST TROP METEOROL,PUNE 411008,MAHARASHTRA,INDIA
JN: INTERNATIONAL JOURNAL OF CLIMATOLOGY, 1997, Vol.17, No.10,
pp.1055-1067
IS: 0899-8418
DT: Article
AB: The association between the mid-latitude circulation and
rainfall over the Indian region on an intraseasonal time-scale
is investigated by considering 11 years (1974-1984) of Northern
Hemisphere 500 hPa geopotential heights and rainfall data for
the Indian summer monsoon months June through to September. On
the basis of extensive correlation analysis between the
geopotential heights and rainfall, it is seen that three
regions over the mid-latitudes, the Manchurian region, the
Algerian region and the Caspian sea region show positive
correlation with rainfall over India, with higher values north
of 20 degrees N latitude. Lead and lag correlations between the
heights at the locations identified above and rainfall over
India reveals that some common element of low-frequency
variability is influencing the mid-latitude circulation and
Indian rainfall.
On the interannual scale the connections between the winter-
time low-frequency patterns (the Pacific/North Atlantic, the
West Pacific Oscillation, the North Atlantic Oscillation and
the Eurasian) and Indian summer monsoon rainfall (ISMR) are
investigated. Only the West Pacific Oscillation pattern shows a
significant relationship with the ISMR. Further, the
interannual and the decadal variability is examined by using
the Northern Hemisphere zonal index data for the period 1900-
1993. Results reveal that the decadal-scale variability of the
ISMR and the circulation features of the Northern Hemisphere
are connected. (C) 1997 by the Royal Meteorological Society.
KP: SOUTHERN OSCILLATION, RAINFALL, TEMPERATURE, AIR, VARIABILITY,
WINTER
WA: Indian monsoon variability, teleconnections, 500 hPa heights,
zonal index
(136) TI: Global climate change and phenotypic variation among red deer
cohorts
AU: Post,E, Stenseth,NC, Langvatn,R, Fromentin,JM
NA: UNIV OSLO,DEPT BIOL,DIV ZOOL,N-0316 BLINDERN,OSLO,NORWAY
UNIV STUDIES SVALBARD,N-9170 LONGYEARBYEN,SPITZBERGEN,NORWAY
JN: PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL
SCIENCES, 1997, Vol.264, No.1386, pp.1317-1324
IS: 0962-8452
DT: Article
AB: The variability of two fitness-related phenotypic traits (body
weight and a mandibular skeletal ratio) was analysed among
cohorts and age-classes of red deer in Norway Phenotypic
variation among cohorts was pronounced for calves, yearlings
and reproductively mature adults. Fluctuations in cohort-
specific mean body weights and skeletal ratios of adults
correlated with global climatic variation in winter conditions
influenced by the North Atlantic Oscillation while cohorts were
in utero. Red deer born following warm winters were smaller
than those born after cold winters, and this inter-cohort
variability persisted into adulthood. Phenotypic variation
among cohorts of red deer influenced by climate change may pose
consequences for fitness of cohorts since body size and
condition contribute to reproductive success and survival in
male and female red deer. In particular, the recent trend of
increasingly warm winters in northern Europe and Scandinavia
may lead to reduced body size and fecundity of red deer, and
perhaps other ungulates, in those areas.
KP: NORTH-ATLANTIC OSCILLATION, MOOSE ALCES-ALCES, BODY-WEIGHT,
POPULATION-DYNAMICS, PLANT PHENOLOGY, CARCASS WEIGHT, WINTERS
SNOW, AGE, REPRODUCTION, PARTURITION
(137) TI: The association between the BWA index and winter surface
temperature variability over eastern Canada and west Greenland
AU: Shabbar,A, Higuchi,K, Skinner,W, Knox,JL
NA: ENVIRONM CANADA,ATMOSPHER ENVIRONM SERV,4905 DUFFERIN
ST,DOWNSVIEW,ON M3H 5T4,CANADA
JN: INTERNATIONAL JOURNAL OF CLIMATOLOGY, 1997, Vol.17, No.11,
pp.1195-1210
IS: 0899-8418
DT: Article
AB: Since about 1970, winter surface temperature data from stations
on coastal eastern Canada and western Greenland have shown
detectable decadal cooling. In this study, we attempt to
understand some aspect of this surface cooling trend by
relating it to the variability of the Canadian Polar Trough
(CPT). In order to facilitate the relationship, we introduce a
new 50 kPa index called the Baffin Island-West Atlantic (BWA)
index which, although reflecting the variability of the western
structure of the North Atlantic Oscillation (NAO), is found to
explain temperature variability better in north-eastern North
America than the structure characterized by the NAO index.
The decadal variability in the winter surface temperature is
found to be associated with the BWA index at a statistically
significant correlation of 0.85. Two distinctive winter climate
regimes are found to exist in the climate record from 1947 to
1995, one before and one after about 1970. Although the
magnitude of the variance does not change significantly from
one regime to the next, the two regimes are characterized by
statistically significantly different means and by two distinct
spectral signatures. Variability before 1970 is dominated by
interannual fluctuations, whereas afterwards much of the
contribution to the variability comes from interdecadal
fluctuations.
Subtraction of the 1947-1969 winter 50 kPa mean height field
from the 1970-1995 mean field shows that the change in the
height field over the Northern Hemisphere is reflected in the
enhancement of the negative phase of the NAO mode (which
corresponds to a strong jet stream over the western Atlantic
and a strong Icelandic low) and of the positive phase of the
Pacific/North America (PNA) mode. (C) 1997 by the Royal
Meteorological Society.
KP: NORTH-ATLANTIC OSCILLATION, OCEAN ATMOSPHERE MODEL, SEA-ICE,
INTERANNUAL VARIABILITY, TRANSIENT RESPONSES, GRADUAL CHANGES,
HEMISPHERE, ANOMALIES, LATITUDES, TELECONNECTIONS
WA: eastern Canada, Baffin Bay and Davis Strait, principal
component analysis, wavelet analysis, spectral analysis,
composite analysis, surface temperature, 50 kPa heights, Baffin
Island West Atlantic index, North Atlantic oscillation
(138) TI: Climate variability of the intensity of synoptic processes in
the North Atlantic midlatitudes
AU: Gulev,SK
NA: PP SHIRSHOV OCEANOL INST,23 KRASIKOVA STR,MOSCOW 117218,RUSSIA
INST MEERESKUNDE,D-2300 KIEL,GERMANY
JN: JOURNAL OF CLIMATE, 1997, Vol.10, No.4, pp.574-592
IS: 0894-8755
DT: Review
AB: Long-term interannual variations of the intramonthly standard
deviations of surface meteorological parameters are studied on
the basis of the North Atlantic Ocean Weather Stations (OWSs)
dataset, To consider the different scales of short-term
synoptic variability, intramonthly statistics were calculated
for 3-h sampled data and for running-mean data as well. Year-
to-year variability is considered in terms of linear trends and
interannual oscillations with characteristic periods of several
years. Intramonthly standard deviations for most of the
parameters tended to decrease during the OWS observational
period. Trends in the parameters for different synoptic-scale
statistics are discussed. Intramonthly statistics, computed for
different averaging scales, demonstrate remarkably different
short-period year to year oscillations;. Some relationships
between the interannual variations of synoptic activity and the
SST anomalies are presented. Intramonthly statistics are found
to be an effective indicator of the North Atlantic Oscillation.
Finally, the possibility of applying results to statistics
computed from climatological datasets and analyses of
meteorological centers is discussed.
KP: SEA-SURFACE TEMPERATURE, ATMOSPHERIC CIRCULATION PATTERNS,
OCEANIC THERMAL RESPONSE, HEAT-FLUX ANOMALIES, STATISTICAL-
ANALYSIS, LATENT-HEAT, WIND DATA, CYCLONE, WINTER, FREQUENCY
(139) TI: Variations in seasonal rainfall in southern Europe during the
present century: Relationships with the North Atlantic
Oscillation and the El Nino Southern Oscillation
AU: Rodo,X, Baert,E, Comin,FA
NA: UNIV BARCELONA,FAC BIOL,DEPT ECOL,CLIMATE IMPACT ANAL
GRP,BARCELONA,SPAIN
UNIV CATHOLIQUE LOUVAIN,INST ASTRON & GEOPHYS G LEMAITRE,B-1348
LOUVAIN,BELGIUM
JN: CLIMATE DYNAMICS, 1997, Vol.13, No.4, pp.275-284
IS: 0930-7575
DT: Article
AB: Analysis of data from seventeen rainfall stations in the
Iberian Peninsula, Balearic Islands and Northern Africa has
revealed significant El Nino-Southern Oscillation (ENSO)
signals in Europe. Both North Atlantic Oscillation (NAO) and
Southern Oscillation (SO) exert an influence on Iberian
climate, but at different temporal and spatial scales. Though
most of the peninsula is under NAO influence in winter, some
stations in the eastern region show no connection with this
phenomenon. The same is found for ENSO, with a positively
correlated region appearing in the eastern part of Spain, while
the rest of the peninsula remains insensitive. The correlation
between ENSO and Iberian rainfall has increased towards the end
of the present century, with strong positive signals spanning
over half of the area studied. The percentage of springtime
variability due to ENSO has similarly increased, reaching up to
50% in certain areas.
We also show how there are outstanding climatic sensors of
these phenomena such as Lake Gallocanta, which manifests a
positive response to ENSO while appears insensitive to NAO.
Common long-term patterns are observed between SOI and an
inferred lake level series, suggesting a constant influence of
the low-frequency component of ENSO throughout the period
considered. Lake drying phases every 14 years reflect the
impact of this signal, approximately every four ENSO events.
KP: SEA-SURFACE TEMPERATURE, INDIAN-SUMMER MONSOON, CLIMATE-CHANGE,
UNITED-STATES, PRECIPITATION, EVENTS, VARIABILITY, AUSTRALIA,
PROPAGATION, ASSOCIATION
(140) TI: Response of a global coupled ocean-atmosphere-sea ice climate
model to an imposed North Atlantic high-latitude freshening
AU: Cai,WJ, Syktus,J, Gordon,HB, OFarrell,S
NA: CSIRO,DIV ATMOSPHER RES,ASPENDALE,VIC 3195,AUSTRALIA
JN: JOURNAL OF CLIMATE, 1997, Vol.10, No.5, pp.929-948
IS: 0894-8755
DT: Article
AB: The response of a coupled oceanic-atmospheric-sea ice climate
model to an imposed North Atlantic high-latitude freshening is
examined. The imposed freshening lasts for 5 yr with a total
salt deficit equivalent to about eight times the observed Great
Salinity Anomaly during the late 1960s and early 1970s.
The thermohaline circulation associated with North Atlantic
Deep Water Formation (NADWF) initially weakens, but it recovers
within 20 yr of the imposed freshening being removed. The
effect of the weakened NADWF is gradually transmitted from high
latitudes to the entire Atlantic Ocean. The response at the
equator lags that at 62 degrees N by about 10 yr. In the
midlatitude (from 30 degrees to 58 degrees N) region, the lag
causes a warming during the initial weakening and a cooling
during the recovery. Changes in the thermohaline circulation
significantly modify the large-scale North Atlantic
circulation. In particular, the barotropic Gulf Stream weakens
by about 18%.
An interesting feature is the dipole structure of the initial
response in sea surface temperature, with cooling in the
sinking region and warming south of it. This dipole structure
plays an important role for the recovery of the NADWF once the
imposed freshening is removed. It increases the surface density
in the sinking region and increases the north-south pressure
gradient. Thus, the conditions set up during the initial
weakening contribute to the recovery process.
Modifications of the thermal structure of the ocean surface
lead to changes in the atmospheric circulation, in particular,
a weakening of the westerlies over the midlatitude North
Atlantic and a southward shift over Western Europe. The North
Atlantic oscillation (NAG) index under the imposed freshening
is negative, consistent with findings from observational
studies. The associated climate changes are similar to those
observed with negative NAO values.
Effects of various oceanic and atmospheric feedbacks are
discussed. The results are also compared with those from ocean-
only models, where the atmosphere-ocean interactions and some
of the oceanic feedbacks are excluded.
KP: GENERAL-CIRCULATION MODEL, THERMOHALINE CIRCULATION,
INTERPENTADAL VARIABILITY, MULTIPLE EQUILIBRIA, SALINITY,
OSCILLATION, TEMPERATURE, TRANSPORTS, WATER, CO2
(141) TI: Control of atmospheric export of dust from North Africa by the
North Atlantic oscillation
AU: Moulin,C, Lambert,CE, Dulac,F, Dayan,U
NA: CEA,CNRS,CTR FAIBLES RADIOACT,F-91198 GIF SUR YVETTE,FRANCE
CEA,LAB MODELISAT CLIMAT & ENVIRONM,F-91191 GIF SUR
YVETTE,FRANCE
SNRC,ENVIRONM & RISK ASSESSMENT SECT,IL-81800 YAVNE,ISRAEL
JN: NATURE, 1997, Vol.387, No.6634, pp.691-694
IS: 0028-0836
DT: Article
AB: AU year long, massive airborne plumes of desert dust from the
Sahara and surrounding regions are exported to the North
Atlantic Ocean(1) and the Mediterranean Sea(2). The mass of
African dust transported in the atmosphere is large-about one
billion tonnes per year (ref. 3)-and it has been suggested that
the windblown dusts have a substantial influence on the
regional radiative budget(4-6). Here we use daily satellite
observations of airborne dusts(7) to obtain an 11-year
regional-scale analysis of dust transport out of Africa. The
substantial seasonal variability over the Atlantic Ocean and
Mediterranean Sea can be explained by the synoptic meteorology,
Interannual variations in dust transport are similar over both
regions, and are well correlated with the climatic variability
defined by the North Atlantic Oscillation(8). This large-scale
climatic control on the dust export is effected through changes
in precipitation and atmospheric circulation over the regions
of dust mobilization and transport, Such natural variability is
so large that it is difficult to resolve any anthropogenic
influences on atmospheric dust loads, such as those due to
desertification or land-use changes. It seems likely that the
North Atlantic Oscillation will also affect the distribution-
and radiative influence of other aerosols.
KP: SAHARAN DUST, BASIN
(142) TI: Climate assessment for 1996
AU: Halpert,MS, Bell,GD
NA: NOAA,NCEP,CLIMATE PREDICT CTR,W-NP52,NSC,RM 605,5200 AUTH
RD,CAMP SPRINGS,MD,20746
NOAA,CLIMATE PREDICT CTR,NCEP,NWS,WASHINGTON,DC
JN: BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY, 1997, Vol.78,
No.5, pp.S1-S49
IS: 0003-0007
DT: Article
AB: The climate of 1996 can be characterized by several phenomena
that reflect substantial deviations from the mean state of the
atmosphere persisting from months to seasons. First, mature
cold-episode conditions persisted across the tropical Pacific
from November 1995 through May 1996 and contributed to large-
scale anomalies of atmospheric circulation, temperature, and
precipitation across the Tropics, the North Pacific and North
America. These anomalies were in many respects opposite to
those that had prevailed during the past several years in
association with a prolonged period of tropical Pacific warm-
episode conditions (ENSO). Second, strong tropical
intraseasonal (Madden-Julian oscillations) activity was
observed during most of the year. The impact of these
oscillations on extratropical circulation variability was most
evident late in the year in association with strong variations
in the eastward extent of the East Asian jet and in the
attendant downstream circulation, temperature, and
precipitation patterns over the eastern North Pacific and
central North America. Third, a return to the strong negative
phase of the atmospheric North Atlantic oscillation (NAG)
during November 1995-February 1996, following a nearly
continuous 15-yr period of positive-phase NAO conditions,
played a critical role in affecting temperature and
precipitation patterns across the North Atlantic, Eurasia, and
northern Africa. The NAO also contributed to a significant
decrease in wintertime temperatures across large portions of
Siberia and northern Russia from those that had prevailed
during much of the 1980s and early 1990s.
Other regional aspects of the short-term climate during 1996
included severe drought across the southwestern United States
and southern plains states during October 1995-May 1996,
flooding in the Pacific Northwest region of the United States
during the 1995/96 and 1996/97 winters, a cold and extremely
snowy 1995/96 winter in the eastern United States, a second
consecutive year of above-normal North Atlantic hurricane
activity, near-normal rains in the African Sahel, above-normal
rainfall across southeastern Africa during October 1995-April
1996, above-normal precipitation for most of the year across
eastern and southeastern Australia following severe drought in
these areas during 1995, and generally near-normal monsoonal
rains in India with significantly below-normal rainfall in
Bangladesh and western Burma.
The global annual mean surface temperature for land and marine
areas during 1996 averaged 0.21 degrees C above the 1961-90
base period means. This is a decrease of 0.19 degrees C from
the record warm year of 1995 but was still among the 10 highest
values observed since 1860. The global land-only temperature
for 1996 was 0.06 degrees C above normal and was the lowest
anomaly observed since 1985 (-0.11 degrees C). Much of this
relative decrease in global temperatures occurred in the
Northern Hemisphere extratropics, where land-only temperatures
dropped from 0.42 degrees C above normal in 1995 to 0.04
degrees C below normal in 1996.
The year also witnessed a continuation of near-record low atone
amounts in the Southern Hemisphere stratosphere, along with an
abnormally prolonged appearance of the ''ozone hole'' into
early December. The areal extent of the ozone hole in November
and early December exceeded that previously observed for any
such period on record. However, its areal extent at peak
amplitude during late September-early October was near that
observed during the past several years.
KP: OUTGOING LONGWAVE RADIATION, SEA-SURFACE TEMPERATURE, 40-50 DAY
OSCILLATION, SOUTHERN OSCILLATION, NORTHERN-HEMISPHERE, WINTER
TEMPERATURES, EL-NINO, CIRCULATION, PRECIPITATION, CONVECTION
(143) TI: Climate variability modes due to ocean-atmosphere interaction
in the central Atlantic
AU: Bojaru,R
NA: NATL INST METEOROL & HYDROL,SOS BUCURESTI PLOIESTI 97,BUCHAREST
71552,ROMANIA
JN: TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY, 1997,
Vol.49, No.3, pp.362-370
IS: 0280-6495
DT: Article
AB: Sea surface temperature (SST) and surface wind patterns from
the central Atlantic are studied using empirical orthogonal
function and canonical correlation analysis. The data set,
which consists of monthly means of SST, zonal and meridional
wind components, spans the interval 1965-1987. North Atlantic
Oscillation (NAO) effects are revealed by the analysis of the
tropical Atlantic variability. The persistence of a NAO phase
for several years seems to be related to the persistence of SST
and wind anomalies through a feedback mechanism which takes
place in the northern tropical Atlantic.
KP: SEA-SURFACE TEMPERATURE, TROPICAL ATLANTIC, NORTHEAST BRAZIL,
GENERAL-CIRCULATION, WINTER TEMPERATURES, GREENLAND, DYNAMICS,
SEESAW, EUROPE
(144) TI: Sea surface temperature changes in the North Sea and their
causes
[Full text delivery]
AU: Becker,GA, Pauly,M
NA: FED MARITIME & HYDROG AGCY,POSTFACH 311220,D-20305
HAMBURG,GERMANY
UNIV TRIER,FACHBEREICH GEOMATH 4,D-54286 TRIER,GERMANY
JN: ICES JOURNAL OF MARINE SCIENCE, 1996, Vol.53, No.6, pp.887-898
IS: 1054-3139
DT: Article
AB: On the basis of 25 years of digitized weekly sea surface
temperature (SST) maps of the North Sea, regional patterns,
decadal changes, and trends are investigated with a view to re-
examining the assumption of a general warming trend, as
suggested by the observation that the years 1989-1994 represent
the mildest winters observed in the past 50, perhaps even 130,
years. A regional classification on the basis of an analysis of
the patterns of SST anomaly fluctuations suggests eight
different regions resembling those identified for the
distribution of the North Sea water mass. The oceanic influence
on the western side and the continental influence on the
eastern side are reflected in the strikingly different
behaviour of the western and eastern North Sea SST. Positive
anomalies usually start in the Southern Eight and move, with a
delay of several weeks, into the central and northern North
Sea. None of the regions shows a temperature trend over the
last 25 years. However, spectral analysis of long time series
and the SST maps clearly indicate climatic fluctuations with a
significant peak at a period of about 8 years, a periodicity
also found in the North Atlantic Oscillation index (NAG).
Salinity at the entrances to the North Sea is high when the NAO
indicates an increased zonal atmospheric circulation, whereas
the correlation between SST anomaly and NAO is quite low in
these areas. By contrast, the correlation is high in the
central North Sea. Changes in the air-sea exchange processes
and advection of heal and salt from the North Atlantic appear
to dominate climatic fluctuations in the North Sea. (C) 1996
International Council for the Exploration of the Sea
WA: climatic fluctuations, North Atlantic Oscillation index, sea
surface temperature
(145) TI: Year-to-year and interdecadal variability in the activity of
intraseasonal fluctuations in the Northern Hemisphere
wintertime circulation
AU: Nakamura,H
NA: PRINCETON UNIV,PROGRAM ATMOSPHER & OCEAN SCI,PRINCETON,NJ,08544
JN: THEORETICAL AND APPLIED CLIMATOLOGY, 1996, Vol.55, No.1-4,
pp.19-32
IS: 0177-798X
DT: Article
AB: Interannual variability in the activity of fluctuations with
subseasonal time scales is investigated based upon observed
data of the extratropical Northern Hemisphere circulation over
the recent 38 winters. Their activity is represented in the
root mean square (RMS) field of filtered geopotential height in
which the fluctuations with time scales between 10 days and a
season are retained. The singular value decomposition (SVD) was
applied to the covariance matrix between the seasonal mean and
RMS fields for the 500-hPa height.
The leading SVD mode for the north Pacific represents the
strong relationship between the polarity of the Pacific/North
American (PNA) pattern in the seasonal-mean anomalies and the
amplitude of a meridionally-oriented dipole-like oscillation
within the season. It tends to be more active when the
seasonal-mean jet stream is strongly diffluent over the central
Pacific than when the jet is extended zonally across the
Pacific. The leading SVD mode for the north Atlantic is
indicative of stronger intraseasonal fluctuations near
Greenland in the presence of anticyclonic seasonal-mean
anomalies associated with the North Atlantic Oscillation (NAG).
The intraseasonal variability in the extratropics is strongly
correlated with the underlying sea surface temperature (SST)
anomalies, and that in the north Pacific also exhibits
significant but rather weak correlation with SST anomalies in
the equatorial Pacific. The activity of the atmospheric
intraseasonal fluctuations is found to be modulated in
accordance with interdecadal variability in the seasonal-mean
circulation and SST.
KP: SEA-SURFACE TEMPERATURE, LOW-FREQUENCY VARIABILITY, ATMOSPHERIC
CIRCULATION, EQUATORIAL PACIFIC, HEIGHT ANOMALIES, SST
ANOMALIES, STORM TRACKS, TIME SCALES, PATTERNS, ATLANTIC
(146) TI: North Atlantic Oscillation
AU: McCartney,M
JN: OCEANUS, 1996, Vol.39, No.2, p.13
IS: 0029-8182
DT: Article
(147) TI: Multiyear variability in the near-surface temperature structure
of the midlatitude western North Atlantic Ocean
AU: Molinari,RL, Mayer,DA, Festa,JF, Bezdek,HF
NA: NOAA,ATLANTIC OCEANOG & METEOROL LAB,ENVIRONM RES LABS,4301
RICKENBACKER CAUSEWAY,MIAMI,FL,33149
JN: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1997, Vol.102, No.C2,
pp.3267-3278
DT: Article
AB: Between 1966 and 1995, subsurface temperature data have been
collected in the western North Atlantic Ocean using expendable
bathythermographs. Data coverage is sparse in both time and
space, but evidence for decadal variability in the upper 400 m
of the water column is found. The data were averaged by month
onto a 2 degrees of latitude by 4 degrees of longitude grid.
Thirty-one quadrangles in the region bounded by 17 degrees N
and 43 degrees N and 78 degrees W and 66 degrees W have
sufficient data to provide consistent results. Anomaly time
series at 0, 100, 200, 300, and 400 m were estimated by
subtracting a mean monthly climatology. The individual records
were detrended and filtered to highlight the longer-period
signals. The analysis resulted in 25-year records (1969-1993)
for study. Within the thermocline of the subtropical gyre and
the Gulf Stream at 100 and 200 m, periods of predominately
positive temperature anomaly end in 1971, 1982, and 1990, while
periods of negative anomaly end in 1976 and 1985. Only the
events ending in 1971, 1976, and 1990 are in the majority of
the records at 300 and 400 m. Most of the events also appear in
the sea surface temperature (SST) records but are somewhat
masked by significant noise at the surface. Meridional-vertical
temperature sections through the subtropical gyre show that
transitions from negative to positive anomaly events are
characterized by a deepening of the isotherms throughout the
section and transitions from positive to negative events by a
rising of the isotherms. Significant lateral migration of the
axis of the Gulf Stream, although possibly masked by the 2
degrees averaging, is not necessary to explain either type of
event. The transitions in the SST and 100-m temperature time
series occur at essentially the same time as the transitions in
an index of the North Atlantic Oscillation (NAG) that has also
been detrended (i.e., 1971, 1976, 1980, 1984, 1988). The 1971,
1976, and 1988 NAO events are also observed at 300 and 400 m as
described earlier. Periods of positive subsurface temperature
anomaly are coincidental with periods of positive NAO index,
and periods of negative subsurface temperature anomaly are
coincidental with periods of negative NAO index. Thus earlier
results showing connections between the NAO and western
Atlantic SST at decadal timescales are now extended to at least
400 m in the water column. Trends were computed from the
individual 25-year records. The trends at all depths are
predominately negative north of 38 degrees N and positive south
of 38 degrees N. Inferences from the horizontal distribution of
the trends and results from earlier studies suggest that the
1969-1993 period may be a phase of a 30- to 50-year signal
observed in the northern Atlantic since the beginning of the
century.
KP: DEPTH
(148) TI: Icelandic low cyclone activity: Climatological features,
linkages with the NAG, and relationships with recent changes in
the Northern Hemisphere circulation
AU: Serreze,MC, Carse,F, Barry,RG, Rogers,JC
NA: UNIV COLORADO,DIV CRYOSPHER & POLAR PROC,CIRES,POB
449,BOULDER,CO,80309
OHIO STATE UNIV,DEPT GEOG,COLUMBUS,OH,43210
JN: JOURNAL OF CLIMATE, 1997, Vol.10, No.3, pp.453-464
IS: 0894-8755
DT: Article
AB: Output from a cyclone detection and tracking algorithm, applied
to twice-dairy sea level pressure (SLP) fields for the period
1966-93, is used to examine the characteristics of cyclone
activity associated with the locus of the mean Icelandic low
(IL), variability during extremes of the North Atlantic
oscillation (NAG), and recent changes in relation to
circulation over the Northern Hemisphere.
Cyclone events within the climatological IL display a modest
seasonal cycle with a winter maximum. However, winter systems
are considerably deeper than their summer counterparts with
much-larger maximum deepening rates. During the cold season
(October-March), IL cyclone intensities are typical of oceanic
systems but exhibit lower maximum deepening rates. During the
warm season (April-September), intensities are typical of
Northern Hemisphere values with deepening characteristics
similar to those for all extratropical oceans. Depending on the
month, 10%-15% (13%-18%) of cyclone events in the IL region
represent local cyclogenesis (cyclolysis). Roughly half of all
IL cyclones correspond to systems showing their first
appearance of a closed isobar north of 55 degrees N, but some
can be traced upstream as far as the southern and northern
Rocky Mountains.
There is a twofold decrease in cold season cyclone events
within the climatological IL during negative extremes of the
NAG, with accompanying reductions in intensity, but little-
change in maximum deepening rates or source regions. This is
associated with modest increases in activity to the south over
a large area from Labrador eastward to Portugal, reflected in
the southward excursion and weakening of the subpolar low.
Despite a change toward a more positive NAO index in recent
years, no significant increases in cold season cyclone activity
are observed in the IL region. However, there have been
significant local increases within the region north of 60
degrees N for both cold and warm seasons. These are most
pronounced over the central Arctic Ocean, associated with
decreases in high-latitude SLP of up to 4 mb. The regional
patterns of altered cyclone activity and SLP are consistent
with recent changes in high-latitude sea ice conditions and
surface temperatures.
KP: STATISTICAL-ANALYSIS, WINTER TEMPERATURES, HIGH-LATITUDES, SEA-
ICE, ATLANTIC, CLIMATE, GREENLAND, PATTERNS, CENTERS, SEESAW
(149) TI: North Atlantic interannual variability in a coupled ocean-
atmosphere model
AU: Delworth,TL
NA: NOAA,GEOPHYS FLUID DYNAM LAB,POB 308,PRINCETON,NJ,08542
JN: JOURNAL OF CLIMATE, 1996, Vol.9, No.10, pp.2356-2375
IS: 0894-8755
DT: Article
AB: The primary mode of sea surface temperature variability in the
North Atlantic or interannual timescales during winter is
examined in a coupled ocean-atmosphere model. The model,
developed at the Geophysical Fluid Dynamics Laboratory, is
global in domain with realistic geography and a seasonal cycle
of insolation. Analyses performed on a 1000-year integration of
this model show that this mode is characterized by zonal bands
of SST anomalies in the North Atlantic and bears a district
resemblance to observational results. The largest anomalies in
the model are to the southeast of Newfoundland.
The model SST variations appear to be related to a north-south
dipole in the atmospheric 500-mb geopotential height field,
which resembles the North Atlantic oscillation and the Western
Atlantic pattern. Analyses are presented that show that this
mode of SST variability is primarily driven by perturbations to
the surface heat fluxes, which are largely governed by
atmospheric variability. Changes in model ocean circulation
also contribute to this mode of variability but appear to be of
secondary importance.
Additional integrations are analyzed to examine the above
conclusion. The same atmospheric model used in the above
integration was coupled to a 50-m slab ocean and integrated for
500 years. The primary mode of SST variability in this model,
in which there were no effects of ocean dynamics, resembles
that primary mode from the coupled model, strengthening the
conclusion that the surface fluxes are the primary mechanism
generating this oceanic variability. One notable difference
between the two models is related to the presence of deep
vertical mixing at high latitudes in the model with a fully
dynamic ocean. An additional 500-year integration of the
atmospheric model with a prescribed seasonal cycle of SSTs lend
further support to this conclusion, as do additional diagnostic
calculations in which a 50-m slab ocean was forced by the time
series of surface fluxes from both the prescribed SST and fully
coupled model.
KP: SEA-SURFACE TEMPERATURE, EXTRATROPICAL SST ANOMALIES, GENERAL-
CIRCULATION MODEL, HEAT-FLUX ANOMALIES, INTERDECADAL VARIATIONS,
TRANSIENT RESPONSES, GRADUAL CHANGES, HEIGHT FIELD, WINTER,
PATTERNS
(150) TI: North Atlantic circulation and variability, reviewed for the
CNLS conference
AU: Talley,LD
NA: UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,LA JOLLA,CA,92093
JN: PHYSICA D, 1996, Vol.98, No.2-4, pp.625-646
IS: 0167-2789
DT: Article
AB: The circulation and water mass structure of the North Atlantic
are reviewed, with emphasis on the large-scale overturning cell
which produces North Atlantic Deep Water (NADW). Properties and
transports for its major components (Nordic Seas Overflow
Water, Labrador Sea Water, Mediterranean Water, Antarctic
Intermediate Water and Antarctic Bottom Water) are reviewed.
The transport estimates and properties of NADW coupled with the
observed meridional heat transport in the Atlantic limit the
temperature of northward flow which replenishes the NADW to the
range 11-15 degrees C. The high salinity of the North Atlantic
compared with other ocean basins is important for its
production of intermediate and deep waters; about one third of
its higher evaporation compared with the North Pacific is due
to the Mediterranean. The evaporation/precipitation balance for
the North Atlantic is similar to the Indian and South Atlantic
Oceans; the difference between the North and South Atlantic may
be that high evaporation in the North Atlantic affects much
greater depths through Mediterranean Water production.
Also described briefly is variability of water properties in
the upper layers of the subtropical/subpolar North Atlantic, as
linked to the North Atlantic Oscillation. The oceanographic
time series at Bermuda is then used to show decadal variations
in the properties of the Subtropical Mode Water, a thick layer
which lies in the upper 500 m. Salinity of this layer and at
the sea surface increases during periods when the North
Atlantic westerlies weaken between Iceland and the Azores and
shift southwestward. (The North Atlantic Oscillation index is
low during these periods). Temperature at the surface and in
this layer are slightly negatively correlated with salinity,
decreasing when salinity increases. It is hypothesized that the
salinity increases result from incursion of saline water from
the eastern subtropical gyre forced by the southward migration
of the westerlies, and that the small temperature decreases are
due to increased convection in the Sargasso Sea, also resulting
from the southward shift of the westerlies.
KP: LABRADOR SEA-WATER, ANTARCTIC INTERMEDIATE WATER, MERIDIONAL
HEAT-TRANSPORT, WESTERN BOUNDARY CURRENT, DEEP-WATER, SOUTH-
ATLANTIC, MEDITERRANEAN WATER, POTENTIAL VORTICITY, GREENLAND
SEA, OCEAN
WA: North Atlantic circulation, water mass production, North
Atlantic Oscillation, decadal ocean variability, Bermuda
oceanographic station
(151) TI: Interannual variability in reconstructed Canadian snow cover,
1915-1992
AU: Brown,RD, Goodison,BE
NA: ATMOSPHER ENVIRONM SERV,2121 TRANS CANADA HIGHWAY,DORVAL,PQ H9P
1J3,CANADA
ATMOSPHER ENVIRONM SERV,DOWNSVIEW,ON,CANADA
JN: JOURNAL OF CLIMATE, 1996, Vol.9, No.6, pp.1299-1318
IS: 0894-8755
DT: Article
AB: Seasonal snow cover information over southern Canada was
reconstructed from daily snowfall and maximum temperature data
back to 1915 using a simple mass balance approach with snowmelt
estimated via a calibrated temperature index method. The
reconstruction method was able to account for 70%-80% of the
variance in annual snow cover duration (SCD) over most of
southern Canada for the 1955-1992 calibration period. The data
were used to construct regional SCD anomaly series in four
regions spanning the continent. The regional SCD series were
characterized by high interannual variability, with most of the
variance concentrated at periods less than 5 years. Spring
(MAM) snow cover variability was characterized by a prominent
spectral peak with a period of approximately 4 years, which
appeared to be linked to tropical Pacific sea surface
temperature variability.
There was no evidence of statistically significant long-term
trends in snow cover in any of the regions, but the data
suggested that winter (DJF) snow cover had increased and spring
snow cover had decreased over much of southern Canada. One of
the most prominent regional features was a systematic decrease
in winter and spring snow cover over the prairies since
approximately 1970. However, current low snow cover values in
this region are still within the expected range of natural
variability. Linear combinations of the regional SCD series,
including data from the Great Plains, were able to explain 81%
and 75% of the variance in North American winter and spring
snow covered area (SCA) over the 1972-1992 period.
Reconstructed values of SCA back to 1915 suggested that North
American winter snow cover has exhibited a gradual increase of
11.0 x 10(3) km(2) yr(-1) during much of this century, while
spring snow cover has decreased by an average -6.0 x 10(3)
km(2) yr(-1). These represent rather small changes in SCA (<10%
of current mean SCA over a 100-yr period).
Of the several teleconnection indices investigated, the
Pacific-North American (PNA) pattern was observed to exert the
strongest influence on snow cover variability; the positive
phase of the PNA pattern was associated with reduced snow cover
in all seasons over western Canada. The influence of ENSO on
snow cover variability was found to be highly variable in both
time and space, with lag 0 correlations indicating that El Nino
was associated with less snow cover over western Canada. These
correlations were much weaker than the PNA pattern. The
influence of the North Atlantic oscillation pattern was
observed to be mainly confined to winter snow cover variations
across the eastern United States and southern Ontario.
KP: AMERICAN TELECONNECTION PATTERN, UNITED-STATES CLIMATE,
NORTHERN-HEMISPHERE, TEMPERATURE PATTERNS, SOUTHERN OSCILLATION,
HEAT-BALANCE, PRECIPITATION, PACIFIC, TRENDS, MODEL
(152) TI: Pinatubo aerosol and stratospheric ozone reduction:
Observations over central Europe
AU: Ansmann,A, Wagner,F, Wandinger,U, Mattis,I, Gorsdorf,U, Dier,HD,
Reichardt,J
NA: INST TROPOSPHER RES,D-04318 LEIPZIG,GERMANY
METEOROL OBSERV LINDENBERG,D-15864 LINDENBERG,GERMANY
GKSS FORSCHUNGSZENTRUM GEESTHACHT GMBH,INST PHYS & CHEM
ANALYT,D-21494 GEESTHACHT,GERMANY
JN: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1996, Vol.101,
No.D13, pp.18775-18785
IS: 0148-0227
DT: Article
AB: Long-term observations of ozone profiles at Lindenberg (52.2
degrees N, 14.1 degrees E) and of profiles of the particle
surface area concentration at Geesthacht (53.4 degrees N, 10.4
degrees E) are evaluated. Six time series of monthly mean ozone
anomalies are formed for layers between 13.5 and 27 km height.
The effects of seasonal variation, trend, quasi-biennial
oscillation (QBO), polar vortex, and North Atlantic oscillation
(NAG) are eliminated. The residual anomalies indicate aerosol-
induced ozone losses between 10 and 30% in the central part of
the Pinatubo layer (15-20 km height) in the winter and spring
seasons of 1991-1992 and 1992-1993. Values of the monthly mean
particle surface area concentration ranged from 10 to 36 mm(2)
m(-3) during this time period. A correlation analysis, based on
mean values of the ozone and aerosol data for the lower,
central, and upper part of the Pinatubo layer, indicates a weak
positive linear relationship between ozone depletion and
surface area in each of the three layers. There is a generally
strong influence of the polar vortex strength on the ozone
concentration in winter. In the winter of 1992-1993, 10 to 60%
of the entire ozone reduction is estimated to be related to the
anomalously strong polar cyclone. After the elimination of the
vortex-induced reduction, winter mean sulfate-related ozone
losses of 10 to 20% were associated with winter mean surface
area concentrations of 15 to 20 mm(2) m(-3) for the first two
winters after the eruption. The observations are compared with
other measurements at northern midlatitudes and with model
calculations. In general, a good agreement is found.
KP: MIDLATITUDE LIDAR BACKSCATTER, NORTHERN-HEMISPHERE WINTER,
RECORD LOW OZONE, HETEROGENEOUS CHEMISTRY, POLAR VORTEX, EL-
CHICHON, MOUNT-PINATUBO, CORRELATED BEHAVIOR, POTENTIAL
VORTICITY, VOLCANIC-ERUPTIONS
(153) TI: The anomalous sea-ice extent in Hudson Bay, Baffin Bay and the
Labrador Sea during three simultaneous NAO and ENSO episodes
AU: Mysak,LA, Ingram,RG, Wang,J, vanderBaaren,A
NA: MCGILL UNIV,CTR CLIMATE & GLOBAL CHANGE RES,805 SHERBROOKE ST
W,MONTREAL,PQ H3A 2K6,CANADA
MCGILL UNIV,DEPT ATMOSPHER & OCEAN SCI,MONTREAL,PQ H3A
2K6,CANADA
JN: ATMOSPHERE-OCEAN, 1996, Vol.34, No.2, pp.313-343
IS: 0705-5900
DT: Article
AB: The nature of the sea-ice extent in Hudson Bay, Baffin Bay and
the Labrador Sea associated with the three strong simultaneous
NAO (North Atlantic Oscillation) and ENSO (EI Nino-Southern
Oscillation) episodes of 1972/73, 1982/83 and 1991/92 is
investigated. During the first year of the 1972/73 episode,
when positive sea surface temperature (SST) anomalies occurred
in the eastern tropical Pacific from January 1972 to February
1973 and the Icelandic Low substantially deepened in winter
1973, there were heavy ice conditions (large positive sea-ice
extent anomalies) in the study region and negative SST
anomalies in the Labrador Sea and northwestern North Atlantic
Ocean, north of 50 degrees N. The anomalous ice conditions are
attributed to the coincident large-scale negative surface air
temperature (SAT) and positive northerly wind anomalies in the
region. Ten years later, during 1982/83, the strongest ENSO
event of the past century occurred and extremely large positive
sea-ice extent anomalies persisted in the Baffin Bay-Labrador
Sea region for almost two years. This response was also due to
negative anomalies in the SAT for much of this period as well
as very strong northerly winds in the Labrador Sea associated
with a deepened Icelandic Low during autumn 1982 and winter
1983. During the winter of 1991/92, severe ice conditions were
observed off Newfoundland in response to local negative SAT
anomalies and a strong NAO event. Cross-correlations between
the regional SAT anomalies and the sea-ice area anomalies, as
well as the SO (Southern Oscillation) and NAO indices for the
period 1953-90, provide further support for the above findings.
KP: GENERAL-CIRCULATION MODEL, ARCTIC CLIMATE CYCLE, FRESH-WATER
CONTENTS, NORTH-ATLANTIC, SOUTHERN OSCILLATION, INTERANNUAL
VARIABILITY, WINTER TEMPERATURES, DECADAL VARIABILITY, AIR-
TEMPERATURE, HIGH-LATITUDES
(154) TI: Influence of variations in extratropical wintertime
teleconnections on Northern Hemisphere temperature
AU: Hurrell,JW
NA: NATL CTR ATMOSPHER RES,CLIMATE & GLOBAL DYNAM DIV,POB
3000,BOULDER,CO,80307
JN: GEOPHYSICAL RESEARCH LETTERS, 1996, Vol.23, No.6, pp.665-668
IS: 0094-8276
DT: Article
AB: Pronounced changes in the wintertime atmospheric circulation
have occurred since the mid-1970s over the ocean basins of the
Northern Hemisphere, and these changes have had a profound
effect on surface temperatures. The variations over the North
Atlantic are related to changes in the North Atlantic
Oscillation (NAG), while the changes over the North Pacific are
linked to the tropics and involve variations in the Aleutian
low with teleconnections downstream over North America.
Multivariate linear regression is used to show that nearly all
of the cooling in the northwest Atlantic and the warming across
Europe and downstream over Eurasia since the mid-1970s results
from the changes in the NAG, and the NAO accounts for 31% of
the hemispheric in terannual variance over the past 50 winters.
Over the Pacific basin and North America, the temperature
anomalies result in part from tropical forcing associated with
the El Nino-Southern Oscillation phenomenon but with important
feedbacks in the extratropics. The changes in circulation over
the past two decades have resulted in a surface temperature
anomaly pattern of warmth over the continents and coolness over
the oceans. This pattern of temperature change has amplified
the observed hemispheric-averaged warming because of its
interaction with land and ocean; temperature changes are larger
over land compared to the oceans because of the small heat
capacity of the former.
KP: SURFACE
(155) TI: Calanus and environment in the eastern North Atlantic .2.
Influence of the North Atlantic Oscillation on C-finmarchicus
and C-helgolandicus
AU: Fromentin,JM, Planque,B
NA: LAB OCEANOG BIOL & ECOL PLANCTON MARIN,URA 2077,STN ZOOL,BP
28,F-06230 VILLEFRANCHE MER,FRANCE
SIR ALISTER HARDY FDN OCEAN SCI,LAB,PLYMOUTH PL1
2PB,DEVON,ENGLAND
JN: MARINE ECOLOGY-PROGRESS SERIES, 1996, Vol.134, No.1-3, pp.111-
118
IS: 0171-8630
DT: Article
AB: The influence of the North Atlantic Oscillation (NAG) on 2
major zooplankton species of the eastern North Atlantic and the
North Sea, Calanus finmarchicus and C. helgolandicus (Copepoda,
Calanoida), was investigated. Our results confirm that from
December to April, west wind stress (WWS) intensity and
temperature are strongly related to the NAG. If these results
were expected, more striking were the close relationships
between NAO and Calanus species abundance. Fluctuations in
abundance of C. finmarchicus mainly result from the combination
of 2 factors, both driven by the NAG: WWS effects on spring
primary production and temperature. The case of C.
helgolandicus is more complicated, as the links between this
species and the NAO result from the combination of several
factors. Two of these factors, spatial heterogeneity of WWS
strength over the area and temperature, are directly driven by
the NAG. The third one, competition between the 2 Calanus
species, is indirectly influenced by the NAG. Biogeographical
boundaries of the 2 copepods are also modified by the NAG.
Thus, in a comparable way to the El Nino Southern Oscillation
in the Pacific, the NAO impacts the pelagic ecosystem of the
eastern Atlantic and the North Sea.
KP: CONTINUOUS PLANKTON RECORDS, EL-NINO, SEA, PACIFIC, TEMPERATURE,
VARIABILITY, CLIMATE, CONSEQUENCES, FLUCTUATIONS, ZOOPLANKTON
WA: North Atlantic Oscillation, Calanus, long-term changes, eastern
North Atlantic, North Sea, continuous Plankton Recorder survey
(156) TI: Northern hemispheric interannual teleconnection patterns and
their changes due to the greenhouse effect
AU: Liang,XZ, Wang,WC, Dudek,MP
NA: SUNY ALBANY,ATMOSPHER SCI RES CTR,ALBANY,NY,12205
JN: JOURNAL OF CLIMATE, 1996, Vol.9, No.2, pp.465-479
IS: 0894-8755
DT: Article
AB: Observed and general circulation climate model (GCM) simulated
interannual teleconnection patterns in the Northern Hemisphere
are compared on a monthly basis. The study was based on 1946-
1991 observations and two separate 100-year simulations
corresponding to the present climate and a greenhouse warming
climate. The teleconnection patterns are characterized by
action centers and composite extreme anomaly (CEA)
distributions. The definition and comparison of observed and
simulated patterns include examination of time persistence,
spatial coherence as well as consistent signatures between 500-
mb height, sea level pressure, and surface air temperature.
For the present climate simulation, the GCM reproduces observed
spatial and temporal variations of the action centers of four
principal teleconnection patterns: the North Atlantic
oscillation, the North Pacific oscillation, the Pacific/North
American pattern, and the Eurasian pattern. Substantial model
biases exist in the magnitude, regional structure as well as
monthly transition of anomalies. The CEA regional
characteristics are better simulated over land than over the
oceans. For example, the model most accurately simulates the
Eurasian pattern, which has its dominant action centers over
Eurasia. In addition, all three climate variables exhibit
substantial anomalies for each land-based action center. In
contrast, over the oceans, the model systematically
underestimates sea level pressure and 500-mb height CEAs, while
it produces small surface temperature responses. It is
suggested that atmospheric dynamics associated with flow
instability is likely to be the dominant mechanism that
generates these teleconnections, while the lack of interactive
ocean dynamics may be responsible for small responses over the
oceans.
In the greenhouse warming climate, the GCM continues to
simulate the four interannual teleconnection patterns.
Systematic changes, however, are found for the Pacific/North
American and Eurasian patterns in winter, where the action
centers shift to the east and the CEAs weaken over land. These
results must be considered to be exploratory because of the use
of a mixed layer ocean that does not include oceanic dynamics.
KP: GEOPOTENTIAL HEIGHT FIELD, RADIATIVELY ACTIVE GASES, SOUTHERN
OSCILLATION, EFFECTIVE CO2, CLIMATE, WINTER, PACIFIC,
VARIABILITY, PREDICTABILITY, FLUCTUATIONS
(157) TI: DECADAL TRENDS IN THE NORTH-ATLANTIC OSCILLATION - REGIONAL
TEMPERATURES AND PRECIPITATION
AU: HURRELL,JW
NA: NATL CTR ATMOSPHER RES,POB 3000,BOULDER,CO,80307
JN: SCIENCE, 1995, Vol.269, No.5224, pp.676-679
IS: 0036-8075
DT: Article
AB: Greenland ice-core data have revealed large decadal climate
variations over the North Atlantic that can be related to a
major source of low-frequency variability, the North Atlantic
Oscillation. Over the past decade, the Oscillation has remained
in one extreme phase during the winters, contributing
significantly to the recent wintertime warmth across Europe and
to cold conditions in the northwest Atlantic. An evaluation of
the atmospheric moisture budget reveals coherent large-scale
changes since 1980 that are linked to recent dry conditions
over southern Europe and the Mediterranean, whereas northern
Europe and parts of Scandinavia have generally experienced
wetter than normal conditions.
KP: LOW-FREQUENCY VARIABILITY, SEA-LEVEL PRESSURE, ATMOSPHERIC
CIRCULATION, HEMISPHERE WINTER, TIME-SCALE, GREENLAND, PATTERNS,
ANOMALIES, EVENT, AREA
(158) TI: ATLANTIC ARCTIC CYCLONES AND THE MILD SIBERIAN WINTERS OF THE
1980S
AU: ROGERS,JC, MOSLEYTHOMPSON,E
NA: OHIO STATE UNIV,BYRD POLAR RES CTR,COLUMBUS,OH,43210
OHIO STATE UNIV,DEPT GEOG,COLUMBUS,OH,43210
JN: GEOPHYSICAL RESEARCH LETTERS, 1995, Vol.22, No.7, pp.799-802
IS: 0094-8276
DT: Article
AB: The winters of the 1980s were among the warmest on record over
northern Siberia. Daily and monthly sea level pressures, 500 mb
heights, and an index of Atlantic storm track extent (toward
the northeast) and intensity, are used to examine atmospheric
circulation variability during extremely warm and cold winter
months in Siberia. In recent years, the comparatively warm
months are associated with an increased frequency in the
passage of intense Atlantic cyclones that enter the extreme
northeastern Atlantic and traverse the Barents and Kara Seas.
These arctic cyclones bring strong westerly flow into Siberia
along with passages of extensive cyclone warm sectors.
Conversely, the surface mean Siberian anticyclone and large-
scale features such as the North Atlantic Oscillation appear to
have little effect on warm Siberian winters.
KP: CLIMATE, SEASON
(159) TI: TRANSIENT EDDY FORCING OF THE ROTATIONAL FLOW DURING NORTHERN
WINTER
AU: HURRELL,JW
NA: NATL CTR ATMOSPHER RES,POB 3000,BOULDER,CO,80307
JN: JOURNAL OF THE ATMOSPHERIC SCIENCES, 1995, Vol.52, No.12,
pp.2286-2301
IS: 0022-4928
DT: Article
AB: The total direct transient eddy forcing of the vorticity
balance in the upper troposphere during northern winter is
examined using 11 years of 2 to 8-day bandpassed global
analyses. Most examinations of the importance of high-frequency
eddy vorticity fluxes to the maintenance of either the
climatological standing waves or low-frequency anomalous Bows
have focused on only the horizontal flow or the rotational
component of the horizontal transient flow. The latter
simplification has been shown to be questionable for planetary
scales. The vorticity flux by the transient divergent flow
produces a forcing of the mean streamfunction that is of
comparable magnitude with the equivalent rotational term.
However, the streamfunction Forcing by the sum of the transient
vertical advection and twisting terms largely balances the
forcing by the vorticity flux convergence associated with the
divergent Row. The result is that the convergence of the eddy
vorticity flux by the total transient flow is not a good
approximation to the total forcing of the long-term mean
streamfunction by the high-frequency eddies. These results are
quantified for the mean northern winter season November-March
1980/81-1990/91.
The respective roles of each transient eddy term in the
vorticity equation in maintaining two large-scale, low-
frequency anomalous flows are also examined. One case involves
a pronounced circulation anomaly that persisted for more than a
decade over the North Pacific, and the second case relates to
the maintenance of extremes mes of the North Atlantic
Oscillation. In both cases, transient vorticity fluxes
systematically reinforce and help to maintain the upper-
tropospheric streamfunction anomalies. Just as for the
climatological standing waves, a consideration of the total
transient eddy forcing of the mean anomalous streamfunction
yields a different interpretation than if only the convergence
of the vorticity flux is considered.
KP: TIME-MEAN FLOW, GENERAL-CIRCULATION MODEL, MIDLATITUDE STORM
TRACKS, LOW-FREQUENCY WAVES, EL-NINO, 3-DIMENSIONAL PROPAGATION,
ATMOSPHERIC CIRCULATION, HEMISPHERE WINTER, STATIONARY WAVES,
ANOMALIES
(160) TI: ROBUSTNESS OF LOW-FREQUENCY CIRCULATION PATTERNS DERIVED FROM
EOF AND ROTATED EOF ANALYSES
AU: CHENG,XH, NITSCHE,G, WALLACE,JM
NA: UNIV WASHINGTON,DEPT ATMOSPHER SCI,SEATTLE,WA,98195
JN: JOURNAL OF CLIMATE, 1995, Vol.8, No.6, pp.1709-1713
IS: 0894-8755
DT: Note
AB: The robustness of low-frequency circulation patterns defined by
unrotated and rotated empirical orthogonal functions (EOFs) are
compared based On the Northern Hemisphere 10-day low-pass
filtered wintertime 500-hPa height field. The Pacific/North
American pattern and the North Atlantic Oscillation are the
most prominent modes of low-frequency variability in the data.
The reproducibility of the spatial patterns derived from EOF
and rotated EOF analysis is assessed by repeating the analysis
on 50 subsets of the data, each comprised of the maps belonging
to 22 randomly selected winters from the 44 winters in the
total record. The results indicate that rotated spatial
patterns are less sensitive to sampling fluctuations than their
unrotated counterparts.
KP: NORTHERN-HEMISPHERE WINTER, HEIGHT FIELD, VARIABILITY
(161) TI: GLOBAL-SCALE MODES OF SURFACE-TEMPERATURE VARIABILITY ON
INTERANNUAL TO CENTURY TIMESCALES
AU: MANN,ME, PARK,J
NA: YALE UNIV,DEPT GEOL & GEOPHYS,KLINE GEOL LAB,POB 208109,NEW
HAVEN,CT,06520
JN: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1994, Vol.99,
No.D12, pp.25819-25833
IS: 0148-0227
DT: Article
AB: Using 100 years of global temperature anomaly data, we have
performed a singular value decomposition of temperature
variations in narrow frequency bands to isolate coherent
spatio-temporal ''modes'' of global climate variability.
Statistical significance is determined from confidence limits
obtained by Monte Carlo simulations. Secular variance is
dominated by a globally coherent trend, with nearly all grid
points warming in phase at varying amplitude. A smaller, but
significant, share of the secular variance corresponds to a
pattern dominated by warming and subsequent cooling in the high
latitude North Atlantic with a roughly centennial timescale.
Spatial patterns associated with significant peaks in variance
within a broad period range from 2.8 to 5.7 years exhibit
characteristic El Nino-Southern Oscillation (ENSO) patterns. A
recent transition to a regime of higher ENSO frequency is
suggested by our analysis. An interdecadal mode in the 15-to-18
years period range appears to represent long-term ENSO
variability. This mode has a sizeable projection onto global-
average temperature, and accounts for much of the anomalous
global warmth of the 1980s. A quasi-biennial mode centered near
2.2-years period and a mode centered at 7-to-8 years period
both exhibit predominantly a North Atlantic Oscillation (NAG)
temperature pattern. A potentially significant ''decadal'' mode
centered on 11-to-12 years period also exhibits an NAG
temperature pattern and may be modulated by the century-scale
North Atlantic variability.
KP: NORTH-ATLANTIC OCEAN, MULTIPLE TIME SCALES, SOUTHERN
OSCILLATION, AIR-TEMPERATURE, MEAN TEMPERATURE, SOLAR-CYCLE,
HEMISPHERE, FLUCTUATIONS, CLIMATE, WINTER
(162) TI: MOISTURE CONDITION IN THE SOUTH-EASTERN USA AND TELECONNECTION
PATTERNS
AU: YIN,ZY
NA: GEORGIA STATE UNIV,DEPT GEOG,ATLANTA,GA,30303
JN: INTERNATIONAL JOURNAL OF CLIMATOLOGY, 1994, Vol.14, No.9,
pp.947-967
IS: 0899-8418
DT: Article
AB: The purpose of this study is to investigate the relationship
between the moisture condition and teleconnection patterns
including the Pacific-North American (PNA) pattern, North
Atlantic Oscillation (NAO), and the El Nino-Southern
Oscillation (ENSO). The February and August Palmer's Drought
Severity Index (PDSI) was used to represent the moisture
condition of the cold and warm seasons in the south-eastern
USA. The teleconnection patterns were represented by the
indices of PNAI, NAOI, and SOI. Composite maps for extreme
values of the teleconnection indices revealed that spatial
variation in the moisture condition is associated with
different phases of the teleconnection patterns. Correlation
analysis indicated that the PNA, NAO, and ENSO are related
mostly to the subregional moisture conditions. Principal
component analysis defined subregions of homogeneous moisture
regimes. Then regression analysis was performed on the scores
of the principal components of the February and August PDSI,
using the teleconnection indices as the independent variables.
The area with its cold-season moisture condition best explained
by the teleconnection patterns is central and south Florida.
The teleconnection indices also explained significant portions
of the variation in the cold-season moisture condition of
Mississippi and Tennessee. The teleconnection patterns in the
previous autumn probably can be used to predict the moisture
condition in the following winter. Compared with the cold
season, the summer teleconnection patterns are less strongly
related to the warm-season moisture condition. Nevertheless,
the relationships between the moisture condition and the
teleconnection patterns are significant statistically. In
addition, the teleconnection patterns in the previous spring
offered some explanations to the spatial patterns in the warm-
season moisture condition in the region.
KP: PRINCIPAL COMPONENTS ANALYSES, DROUGHT SEVERITY INDEX, DOMAIN
SHAPE, NORTHERN HEMISPHERE, UNITED-STATES, OSCILLATION, CLIMATE,
WINTER, ROTATION, PACIFIC
WA: MOISTURE CONDITION, SOUTH-EASTERN USA, PALMERS DROUGHT SEVERITY
INDEX, TELECONNECTION PATTERNS, PRINCIPAL COMPONENT ANALYSIS
(163) TI: ARCTIC SEA-ICE VARIABILITY ON A TIMESCALE OF WEEKS AND ITS
RELATION TO ATMOSPHERIC FORCING
AU: FANG,ZF, WALLACE,JM
NA: UNIV WASHINGTON,DEPT ATMOSPHER SCI,AK-40,SEATTLE,WA,98195
CHENGDU INST METEOROL,CHENGDU,PEOPLES R CHINA
JN: JOURNAL OF CLIMATE, 1994, Vol.7, No.12, pp.1897-1914
IS: 0894-8755
DT: Article
AB: Northern Hemisphere sea ice concentration, 500-hPa height, sea
level pressure, and 1000-500-hPa thickness at 7-day intervals
are examined for the period 1972-1989, with emphasis on the
winter season. The temporal variability of sea ice
concentration is largest along the climatological mean ice edge
where its frequency distribution is strongly bimodal with ice-
free and ice-covered conditions being observed much more
frequently than partial ice cover. These results confirm
impressions, based on visual inspection of satellite imagery,
that most of the variability in these regions is associated
with the advance and retreat of the ice edge.
Relationships between large-scale patterns of atmospheric
variability and sea ice variability are investigated, making
use of singular value decomposition of the temporal covariance
matrix. The analysis is conducted separately for the Atlantic
and Pacific sectors. In agreement with earlier studies based
upon monthly mean data on sea ice concentration, the strongest
sea ice pattern is comprised of a dipole with opposing centers
of action in the Davis Straits/Labrador Sea region and the
Greenland and Barents seas. Its temporal variability is
strongly coupled to the atmospheric North Atlantic oscillation
(NAG). The relationship between the two patterns is strongest
with the atmosphere leading the ocean by two weeks. An
analogous dipole pattern is observed in the Pacific sector,
with opposing centers of action in the Bening Sea and the Sea
of Okhotsk, which is related to a distinctive pattern of
atmospheric circulation anomalies in the Pacific sector. One
polarity of the NAO and its Pacific counterpart is associated
with blocking episodes, during which the influence of the
atmosphere is strong enough to temporarily halt the
climatological mean advance of the ice edge in some regions and
substantially accelerate it in others.
The relationships between the fields is indicative of local
forcing of sea ice in most regions, with wind stress and
thermodynamic fluxes at the air-sea interface both
contributing. A possible exception is the Greenland Sea, where
it may be necessary to invoke some form of remote forcing in
order to explain the observed changes on the interannual time
scale.
KP: NORTHERN-HEMISPHERE WINTER, STOCHASTIC CLIMATE MODELS, SURFACE
TEMPERATURE, ANOMALIES, GREENLAND, FLUCTUATIONS, CIRCULATION,
PATTERNS, EXTENT, SEESAW
(164) TI: INTERANNUAL VARIABILITY OF SEA-ICE COVER IN HUDSON-BAY, BAFFIN-
BAY AND THE LABRADOR SEA
AU: WANG,J, MYSAK,LA, INGRAM,RG
NA: MCGILL UNIV,CTR CLIMATE & GLOBAL CHANGE RES,MONTREAL H3A
2K6,QUEBEC,CANADA
MCGILL UNIV,DEPT ATMOSPHER & OCEAN SCI,MONTREAL H3A
2K6,QUEBEC,CANADA
JN: ATMOSPHERE-OCEAN, 1994, Vol.32, No.2, pp.421-447
IS: 0705-5900
DT: Article
AB: The spatial and temporal relationships between subarctic
Canadian sea-ice cover and atmospheric forcing are investigated
by analysing sea-ice concentration, sea-level pressure and
surface air temperature data from 1953 to 1988. The sea-ice
anomalies in Hudson Bay, Baffin Bay and the Labrador Sea are
found to be related to the North Atlantic Oscillation (NAO) and
the Southern Oscillation (SO). Through a spatial Student's t-
test and a Monte Carlo simulation, it is found that sea-ice
cover in both Hudson Bay and the Baffin Bay-Labrador Sea region
responds to a Low/Wet episode of the SO (defined as the period
when the SO index becomes negative) mainly in summer. In this
case, the sea-ice cover has a large positive anomaly that
starts in summer and continues through to autumn. The ice
anomaly is attributed to the negative anomalies in the regional
surface air temperature record during the summer and autumn
when the Low/Wet episode is developing. During strong winter
westerly wind events of the NAO, the Baffin Bay--Labrador Sea
ice cover in winter and spring has a positive anomaly due to
the associated negative anomaly in surface air temperature.
During the years in which strong westerly NAO and Low/Wet SO
events occur simultaneously (as in 1972/73 and 1982/83), the
sea ice is found to have large positive anomalies in the study
region; in particular, such anomalies occurred for a major
portion of one of the two years. A spectral analysis shows that
sea-ice fluctuations in the Baffin Bay-Labrador Sea region
respond to the SO and surface air temperature at about 1.7-, 5-
and 10-year periods. In addition, a noticeable sea-ice. change
was found (i.e. more polynyas occurred) around the time of the
so-called ''climate jump '' during the early 1960s. Data on ice
thickness and on ice-melt dates from Hudson Bay are also used
to verify some of the above findings.
KP: SOUTHERN OSCILLATION, WINTER TEMPERATURES, NORTHERN EUROPE,
LEVEL PRESSURE, FLUCTUATIONS, ANOMALIES, GREENLAND, OCEAN,
EXTENT, SEESAW
(165) TI: AN ANALYSIS OF REGIONAL CLIMATE-CHANGE IN SWITZERLAND
AU: BENISTON,M, REBETEZ,M, GIORGI,F, MARINUCCI,MR
NA: ETH,WINTERTHURERSTR 190,CH-8057 ZURICH,SWITZERLAND
UNIV FRIBOURG,CH-1700 FRIBOURG,SWITZERLAND
NATL CTR ATMOSPHER RES,BOULDER,CO,80307
JN: THEORETICAL AND APPLIED CLIMATOLOGY, 1994, Vol.49, No.3,
pp.135-159
IS: 0177-798X
DT: Article
AB: An analysis of daily climatological data covering the period
from 1901 to 1992 for four locations in Switzerland (Zurich,
Lugano, Davos, and Santis) has been made. The study has
highlighted the fact that climate change this century is
characterized by increases in minimum temperatures of about 2K,
a more modest increase in maximum temperatures (in some
instances a decrease of maxima in the latter part of the
record), little trend in the precipitation data, and a general
decrease of sunshine duration through to the mid 1980s. The
interannual variability is generally large, and filtering of
the data to remove high-frequency noise shows that the regional
climate undergoes a series of fluctuations of between 8 and 20
years' duration. The temperature change over this century is of
greater magnitude than the global temperature changes published
in the literature, reflecting an amplification of the global
signal in the Alpine region; warming has been most intense in
the 1940s, followed by the 1980s; the cooling which intervened
from the 1950s to the late 1970s was not sufficient to offset
the warming in the middle of the century.
Pressure statistics have been compiled as a means of providing
a link between the regional-scale climatological variables and
the synoptic, supra-regional scale. These statistics show that
pressure also exhibits a number of decadal-scale fluctuations,
with the appearance of a new and anomalous behavior in the
1980s; in this decade, pressure reaches annual average values
far higher than at other times this century. The pressure field
is well correlated with the North Atlantic Oscillation (NAO)
Index for distinct periods of the record (1931-1950 and 1971-
1990) and is almost decorrelated from the NAO Index for the
other decades of the century; this is indicative of transition
from one climatic regime to another, dominated by zonal flow
when the correlation with the NAO Index is high. In the 1980s,
when zonal flow over the North Atlantic is strong, episodes of
persistent, anomalously high pressures (blocking highs) are
seen to occur over Switzerland, particularly during the winter
season. The difference between the zonal and non-zonal regimes
is particularly marked between the decade of the 1950s and that
of the 1980s.
The impact of this change between the 1950s and the 1980s on a
number of climatological variables has been investigated
statistically in order to provide an illustration of the manner
in which changes in synoptic regimes (i.e., 'climate change')
impacts upon climate characteristics on a regional scale. The
analysis shows that temperature, precipitation, snow depth, and
sunshine duration are indeed sensitive to large-scale
influences; not only can yearly mean changes be quantified, but
also seasonal and monthly fluctuations.
KP: NORTHERN-HEMISPHERE, TEMPERATURE, VARIABILITY
(166) TI: NAO AND SEA-SURFACE TEMPERATURE SIGNATURES IN TREE-RING RECORDS
FROM THE NORTH-ATLANTIC SECTOR
AU: DARRIGO,RD, COOK,ER, JACOBY,GC, BRIFFA,KR
NA: LAMONT DOHERTY EARTH OBSERV,TREE RING LAB,PALISADES,NY,10964
UNIV E ANGLIA,CLIMAT RES UNIT,NORWICH NR4 7TJ,NORFOLK,ENGLAND
JN: QUATERNARY SCIENCE REVIEWS, 1993, Vol.12, No.6, pp.431-440
IS: 0277-3791
DT: Article
AB: Temperature-sensitive tree-ring chronologies from Scandinavia
and Labrador are, respectively, analyzed for their response to
two major features of North Atlantic climate variability: (1)
the North Atlantic Oscillation (NAO), and (2) Coastal and near-
coastal surface air and sea surface temperatures (SSTs). (1)
NAO: Using superposed epoch analysis (SEA), below (above)
average ring-width departures from Scandinavian scots pine
(Pinus sylvestris L.) were found to follow positive (negative)
anomalies in winter (December-February) sea level pressure
(SLP) related to the Icelandic low pressure cell, a key element
of the NAO. In addition to a documented summer temperature
relationship, these trees show a positive correlation with
winter temperatures for Oslo, Norway. Oslo data are used to
define the northwest European end of the winter temperature
seesaw, another major feature of the NAO. Below (above) average
tree-growth departures tend to follow Greenland Above, GA or
(Greenland Below, GB) seesaw winters, which are associated with
high (low) pressure and cold (warm) conditions over
Scandinavia. (2) SSTs: Growing season (April-September)
land/sea temperatures were reconstructed for three 5-degrees x
5-degrees gridcells (50-55-degrees-N, 50-65-degrees-W) near the
coast of Labrador for the period from 1813 to 1988. The tree-
ring data used in this case were four maximum latewood density
chronologies of white spruce (Picea glauca [Moench] Voss) from
sites in southern and central Labrador. An alternative model,
based on only two chronologies, allows extension of these
reconstructions back to 1713. The reconstructions explain about
45% of the temperature variance from 1915-1988 and pass several
tests for model validation with high levels of statistical
significance. They primarily provide information on short-
period (< 10 years) temperature variability for the Labrador
region.
KP: SOUTHERN OSCILLATION, SUMMER TEMPERATURES, WINTER TEMPERATURES,
CIRCULATION, EUROPE, WIDTH, FREQUENCY, GREENLAND, PATTERNS,
DENSITY
(167) TI: OBSERVED CORRELATIONS BETWEEN WINTER-MEAN TROPOSPHERIC AND
STRATOSPHERIC CIRCULATION ANOMALIES
AU: BALDWIN,MP, CHENG,XH, DUNKERTON,TJ
NA: NW RES ASSOCIATES,POB 3027,BELLEVUE,WA,98009
JN: GEOPHYSICAL RESEARCH LETTERS, 1994, Vol.21, No.12, pp.1141-1144
IS: 0094-8276
DT: Article
AB: It is shown that interannual variability of the northern winter
stratospheric flow in 1964-1993 was closely linked to large-
scale circulation anomalies in the middle troposphere. Of the
known tropospheric teleconnection patterns, the one having the
strongest relation to the DJF zonal-mean stratospheric flow was
the North Atlantic Oscillation (NAO). Singular value
decomposition between the 500 and 50-hPa geopotential heights
produced a 500-hPa structure containing elements of the NAO
pattern, but including an anomaly in eastern Siberia. During
this time period, the correlation of NAO-related modes to the
polar lower stratosphere exceeded that of the equatorial quasi-
biennial oscillation.
KP: QUASI-BIENNIAL OSCILLATION, NORTHERN-HEMISPHERE WINTER,
INTERANNUAL VARIABILITY, MB
(168) TI: THE NORTH-ATLANTIC OSCILLATION SIGNATURE IN DEUTERIUM AND
DEUTERIUM EXCESS SIGNALS IN THE GREENLAND ICE-SHEET PROJECT-2
ICE CORE, 1840-1970
AU: BARLOW,LK, WHITE,JWC, BARRY,RG, ROGERS,JC, GROOTES,PM
NA: UNIV COLORADO,INST ARCTIC & ALPINE RES,DEPT GEOL SCI,CB
450,BOULDER,CO,80309
UNIV COLORADO,COOPERAT INST RES ENVIRONM SCI,DEPT
GEOG,BOULDER,CO,80309
UNIV WASHINGTON,QUATERNARY ISOTOPE LAB,SEATTLE,WA,98195
OHIO STATE UNIV,DEPT GEOG,COLUMBUS,OH,43210
JN: GEOPHYSICAL RESEARCH LETTERS, 1993, Vol.20, No.24, pp.2901-2904
IS: 0094-8276
DT: Article
AB: The Greenland Ice Sheet Project 2 (GISP2) core can enhance our
understanding of the relationship between parameters measured
in the ice in central Greenland and variability in the ocean,
atmosphere, and cryosphere of the North Atlantic Ocean and
adjacent land masses. Seasonal (summer, winter) to annual
responses of deltaD and deuterium excess isotopic signals in
the GISP2 core to the seesaw in winter temperatures between
West Greenland and northern Europe from A D. 1840 to 1970 are
investigated. This seesaw represents extreme modes of the North
Atlantic Oscillation, which also influences sea surface
temperatures (SSTs), atmospheric pressures, geostrophic wind
strength, and sea ice extents beyond the winter season.
Temperature excursions inferred from the deltaD record during
seesaw/extreme NAO mode years move in the same direction as the
West Greenland side of the seesaw. Symmetry with the West
Greenland side of the seesaw suggests a possible mechanism for
damping in the ice core record of the lowest decadal
temperatures experienced in Europe from A.D. 1500 to 1700.
Seasonal and annual deuterium excess excursions during seesaw
years show negative correlation with deltaD. This suggests an
isotopic response to a SST/ land temperature seesaw. The
isotopic record from GISP2 may therefore give information on
both ice sheet and sea surface temperature variability. Cross-
plots of deltaD and d show a tendency for data to be grouped
according to the prevailing mode of the seesaw, but do not
provide unambiguous identification of individual seesaw years.
A combination of ice core and tree ring data sets may allow
more confident identification of GA and GB (extreme NAO mode)
years prior to 1840.
KP: SEA-LEVEL PRESSURE, WINTER TEMPERATURES, FREQUENCY, SEESAW,
EUROPE
(169) TI: INTERANNUAL VARIABILITY OF SURFACE CYCLONE TRACKS, ATMOSPHERIC
CIRCULATION PATTERNS, AND PRECIPITATION PATTERNS, IN WINTER
AU: UENO,K
NA: UNIV TSUKUBA,INST GEOSCI,TSUKUBA,IBARAKI 305,JAPAN
JN: JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN, 1993, Vol.71,
No.6, pp.655-671
IS: 0026-1165
DT: Article
AB: Three major teleconnection patterns prevailing at 500 hPa
height, e. g., North Atlantic Oscillation (NAO), Pacific-North
American (PNA) and Western Pacific (WP) patterns, are
investigated in the northern Winter season associated with
cyclone tracks and precipitation patterns. Cyclone position and
tracks, objectively analyzed using NCAR Sea Level Pressure
Grids (1964-1990) and ECMWF 1000 hPa height grids (1980-1990),
are composited in reference to the extreme appearance of
positive or negative teleconnection patterns around the
Atlantic and Pacific. The correlations between the
teleconnections and the inter-annual variability of
precipitation are also investigated.
Significant changes of major cyclone routes are commonly and
clearly found in the two data sets as follows. In case of +/-
NAO patterns, major zonal cyclone tracks fluctuate
meridionally, and cyclones tend to move eastward in the middle
parts of North Atlantic, or they direct northeastward along the
northwestern Atlantic to reach the Norwegian Sea. Significant
variations of precipitation associated with these changes of
cyclone tracks are found in southwestern and northwestern parts
of the west coast of Europe. In the case of dominant +/-PNA
patterns, cyclones tend to direct eastward within 40-degrees-
50-degrees-N over the North Pacific and turn north to migrate
to the Gulf of Alaska to Bristol Bay, or they move
northeastward along the northwestern edge of Pacific to migrate
to the Bering Sea or strike on the east coast of Canada. The
former pattern corresponds to a strengthening of the eastern
part of the Aleutian low, and the latter pattern provides the
positive correlation with precipitation on the east coast of
Japan and a part of the west coast of Canada. Dominant +/-WP
patterns are responsible for the meridional fluctuations of
apparent zonal distribution of cyclone tracks with its strike
of a SSW-NNE direction over the Northern Pacific. The northward
shift of this distribution provides the increase of the
precipitation amount in the southwestern islands and central
Pacific regions of Japan.
(170) TI: THE WESTERN BALTIC SEA-ICE SEASON IN TERMS OF A MASS-RELATED
SEVERITY INDEX - 1879-1992 .1. TEMPORAL VARIABILITY AND
ASSOCIATION WITH THE NORTH-ATLANTIC OSCILLATION
AU: KOSLOWSKI,G, LOEWE,P
NA: BUNDESAMT SEESCHIFFAHRT & HYDROG,BERNHARD NOCHT STR 78,D-20359
HAMBURG,GERMANY
JN: TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY, 1994,
Vol.46, No.1, pp.66-74
IS: 0280-6495
DT: Article
AB: The variability of the severity of ice winters in the Western
Baltic between 1879 and 1992 is statistically investigated
using a time series of the accumulated areal ice volume (or
V(ASIGMA) from the Baltic coast of Schleswig-Holstein. Lowpass
filtering of the original time series shows the level of ice
production in the mid 1980s to have been the same as that
almost 100 years ago. A vivid interpretation is made possible
of the variations in ice production by classifying V(ASIGMA)
according to ice winter severity types. The increased
variability of ice production since the 1920s is seen in the
more frequent occurrence both of very strong and weak ice
winters, while moderate and strong ice winters have decreased.
The time series of the accumulated areal ice volume is
negatively correlated with a temporally corresponding series of
the NAO winter index, a measure of the strength of the zonal
atmospheric circulation above the North Atlantic. Pearson's
correlation coefficient, r(p) = -0.47. exceeds the 99.9 %
confidence limit. In addition, a contingency table analysis
revealed that this inverse correlation is due to the
preferential occurrence of (a) weak ice winters with strong
westerlies (NAO winter index > 1 ) and (b) strong to very
strong ice winters with weak westerlies (NAO winter index < -
1).
(171) TI: MULTIPLE FLOW REGIMES IN THE NORTHERN-HEMISPHERE WINTER .1.
METHODOLOGY AND HEMISPHERIC REGIMES
AU: KIMOTO,M, GHIL,M
NA: UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,CTR CLIMATE DYNAM,405
HILGARD,LOS ANGELES,CA,90024
JAPAN METEOROL AGCY,METEOROL RES INST,TSUKUBA,JAPAN
UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS
ANGELES,CA,90024
JN: JOURNAL OF THE ATMOSPHERIC SCIENCES, 1993, Vol.50, No.16,
pp.2625-2643
IS: 0022-4928
DT: Article
AB: Recurrent and persistent flow patterns are identified by
examining multivariate probability density functions (PDFs) in
the phase space of large-scale atmospheric motions. This idea
is pursued systematically here in the hope of clarifying the
extent to which intraseasonal variability can be described and
understood in terms of multiple flow regimes.
Bivariate PDFs of the Northern Hemisphere (NH) wintertime
anomaly heights at 700 mb are examined in the present paper,
using a 37-year dataset. The two-dimensional phase plane is
defined by the two leading empirical orthogonal functions
(EOFs) of the anomaly fields. PDFs on this plane exhibit
synoptically intriguing and statistically significant
inhomogeneities on the periphery of the distribution. It is
shown that these inhomogeneities are due to the existence of
persistent and recurrent anomaly patterns, well-known as
dominant teleconnection patterns; that is, the Pacific/North
American (PNA) pattern, its reverse, and zonal and blocked
phases of the North Atlantic Oscillation (NAO). It is argued
that the inhomogeneities are obscured when PDFs are examined in
a smaller-dimensional subspace than dynamically desired.
KP: EMPIRICAL ORTHOGONAL FUNCTIONS, 500-MB HEIGHT FLUCTUATIONS,
LOW-FREQUENCY VARIABILITY, QUASI-STATIONARY STATES, SHORT-TIME
SCALES, WEATHER REGIMES, PERSISTENT ANOMALIES, ATMOSPHERIC
CIRCULATION, OBSERVATIONAL EVIDENCE, SOUTHERN-HEMISPHERE
(172) TI: SURFACE CLIMATE VARIATIONS OVER THE NORTH-ATLANTIC OCEAN DURING
WINTER - 1900-1989
AU: DESER,C, BLACKMON,ML
NA: UNIV COLORADO,NOAA,COOPERAT INST RES ENVIRONM SCI,CAMPUS BOX
449,BOULDER,CO,80309
NOAA,CLIMATE MONITORING & DIAGNOST LAB,DIV CLIMATE
RES,BOULDER,CO,80303
JN: JOURNAL OF CLIMATE, 1993, Vol.6, No.9, pp.1743-1753
IS: 0894-8755
DT: Article
AB: The low-frequency variability of the surface climate over the
North Atlantic during winter is described, using 90 years of
weather observations from the Comprehensive Ocean-Atmosphere
Data Set. Results are based on empirical orthogonal function
analysis of four components of the climate system: sea surface
temperature (SST), air temperature, wind, and sea level
pressure. An important mode of variability of the wintertime
surface climate over the North Atlantic during this century is
characterized by a dipole pattern in SSTs and surface air
temperatures, with anomalies of one sip east of Newfoundland,
and anomalies of the opposite polarity off the southeast coast
of the United States. Wind fluctuations occur locally over the
regions of large surface temperature anomalies, with stronger-
than-normal winds overlying cooler-than-normal SSTs. This mode
exhibits variability on quasi-decadal and biennial time scales.
The decadal fluctuations are irregular in length, averaging
approximately 9 years before 1945 and approximately 12 years
afterward. There does not appear to be any difference between
the wind-SST relationships on the different time scales. The
decadal fluctuations in SSTs east of Newfoundland are closely
linked to decadal variations in sea ice in the Labrador Sea,
with periods of greater than normal sea ice extent preceding by
approximately 2 years periods of colder-than-normal SSTs east
of Newfoundland.
Another dominant mode of variability is associated with the
global surface warming trend during the 1920s and 1930s. The
patterns of SST and air temperature change between 1900-29 and
1939-68 indicate that the warming was concentrated along the
Gulf Stream east of Cape Hatteras. Warming also occurred over
the Greenland Sea and the eastern subtropical Atlantic. The
warming trend was accompanied by a decrease in the strength of
the basin-scale atmospheric circulation (negative phase of the
North Atlantic Oscillation). In marked contrast to the dipole
pattern, the wind changes occurred downstream of the largest
SST anomalies; hence, the gradual surface warming along the
Gulf Stream may have been a result of altered ocean currents
rather than local wind forcing.
KP: GENERAL-CIRCULATION MODEL, TEMPERATURE, SEA, VARIABILITY,
SALINITY, FLUCTUATIONS, PATTERNS, TRENDS
(173) TI: STRUCTURE AND SEASONALITY OF INTERANNUAL AND INTERDECADAL
VARIABILITY OF THE GEOPOTENTIAL HEIGHT AND TEMPERATURE-FIELDS
IN THE NORTHERN-HEMISPHERE TROPOSPHERE
AU: WALLACE,JM, ZHANG,Y, LAU,KH
NA: UNIV WASHINGTON,DEPT ATMOSPHER SCI,AK-40,SEATTLE,WA,98195
UNIV WASHINGTON,JOINT INST STUDY ATMOSPHERE &
OCEAN,SEATTLE,WA,98195
JN: JOURNAL OF CLIMATE, 1993, Vol.6, No.11, pp.2063-2082
IS: 0894-8755
DT: Article
AB: Spatial Patterns and seasonality of interannual and
interdecadal variability in the 500-hPa geopotential height,
sea level Pressure, and 1000-500-hPa thickness field are
examined based on NMC analyses over the Northern Hemisphere
extratropics from 1946 onward. The leading empirical orthogonal
function (EOF) of wintertime seasonal mean 500-hPa height is
closely related to the Pacific/North American (PNA)
teleconnection pattern. The time series of its expansion
exhibits a trend from predominantly negative values (below-
normal heights over western Canada) in the early part of the
record to predominantly positive values during the 1980s. The
leading EOF of sea level pressure, which is similar in summer
and winter, contains elements of the North Atlantic Oscillation
(NAO) and a zonally symmetric ''seesaw'' between polar and
temperature latitudes. Its expansion coefficient exhibits
relatively little memory from season to season or from year to
year.
The leading EOFs of summertime and annual-mean 500-hPa height
and thickness are of the same polarity throughout almost the
entire hemisphere. The time series of their expansion
coefficients are strongly correlated with the time series of
hemispheric-mean thickness. We refer to such modes as
manifestations of a ''background field'' whose linear
dependence on hemispheric-mean temperature is more important
than the details of its spatial structure. Such a background
field is evidently present year-round, but it shows up most
clearly during summer when the PNA pattern and other regional
teleconnection patterns are weakest. The fact that it is more
pronounced in the thickness field than in the geopotential
height field suggests that it is primarily associated with
thermal, rather than dynamical, variability. The time series of
its expansion coefficient is dominated by variations on the
interdecadal time scale: it accounts for half the
hemispherically integrated variance of the thickness field
associated with perturbations with periods longer than five
years. The large and possibly spurious drop in hemispherically
averaged thickness and 500-hPa height in the NMC analyses
between 1955 and 1963 contributes substantially to the variance
associated with the background field, but the leading modes of
the summertime and annual-mean thickness fields remain strongly
correlated with one another and with hemispheric-mean thickness
even when the years prior to 1963 are excluded from the record.
Surface air temperature data exhibit qualitatively similar
behavior, as does the extratropical Northem Hemisphere 830-515-
hPa thickness field derived from a 100-year GCM simulation in
which sea surface temperature is prescribed in accordance with
the climatological mean annual cycle.
The long-term trend in the wintertime PNA-like pattern, with
rising heights and temperatures over western Canada, has
contributed substantially to the rather large rise in
hemispheric-mean wintertime surface air temperature since the
late 1970s but it has had little if any effect on the
hemispheric mean temperature aloft, or on summertime surface
air temperatures, which did not rise enough to completely
offset the declines in the 1950s and early 1960s.
KP: PATTERNS, WINTER, CIRCULATION, SURFACE, TRENDS
(174) TI: THE FREEZE RISK TO FLORIDA CITRUS .2. TEMPERATURE VARIABILITY
AND CIRCULATION PATTERNS
AU: DOWNTON,MW, MILLER,KA
NA: NATL CTR ATMOSPHER RES,POB 3000,BOULDER,CO,80307
JN: JOURNAL OF CLIMATE, 1993, Vol.6, No.2, pp.364-372
IS: 0894-8755
DT: Article
AB: Severe freezes are a serious problem for the citrus growers of
central Florida. To investigate possible climatic causes of
intermittent freezes, this paper examines the influence of
several atmospheric circulation patterns on winter temperatures
in Florida. The Pacific/North American pattern is shown to be
particularly influential and the North Atlantic Oscillation
also to be significant, while the Southern Oscillation does not
show a direct effect. A decreasing trend in Florida winter
temperatures since 1947 can be explained by fluctuations in the
former two circulation patterns. Climate model studies to
investigate possible changes in the frequency or location of
these circulation patterns could suggest potential changes in
the freeze risk associated with climatic change.
KP: SOUTHERN OSCILLATION, NORTHERN HEMISPHERE, UNITED-STATES,
CLIMATE, WINTER, PRECIPITATION, FREQUENCY
(175) TI: INTERANNUAL VARIABILITY OF WINTERTIME SNOW COVER ACROSS THE
NORTHERN-HEMISPHERE
AU: GUTZLER,DS, ROSEN,RD
NA: NOAA,ERL,AERON LAB,REAL3,325 BROADWAY,BOULDER,CO,80303
ATMOSPHER & ENVIRONM RES INC,CAMBRIDGE,MA
JN: JOURNAL OF CLIMATE, 1992, Vol.5, No.12, pp.1441-1447
IS: 0894-8755
DT: Article
AB: Digitized maps of Northern Hemisphere snow cover derived from
visible satellite imagery are examined to assess the
interannual variability of snow cover in winter months for
years 1972-90. The secular trend of winter snow cover over the
landmasses of Eurasia and North America during this period is
extremely small in December and January. A decreasing trend of
somewhat larger magnitude is observed in Eurasian snow cover in
February. Fluctuations of detrended interannual snow-cover
anomalies averaged over the Eurasian and North American
continents are positively correlated. By subdividing the
continents into longitudinal sectors it is determined that this
intercontinental relationship is due to high correlations
between European and North American sector's. The relationship
of snow-cover fluctuations to large-scale circulation anomalies
is described using time series of teleconnection pattern
indices derived from monthly mean geopotential height fields. A
pattern of height anomalies resembling the North Atlantic
Oscillation is correlated with snow-cover anomalies in North
America and Europe. The Pacific-North American teleconnection
pattern is highly correlated with snow-cover anomalies in
western North America but has limited influence on
intercontinental snow-cover fluctuations.
(176) TI: RECENT VARIATIONS IN 700 HPA GEOPOTENTIAL HEIGHTS IN SUMMER
OVER EUROPE AND THE MIDDLE-EAST, AND THEIR INFLUENCE ON OTHER
METEOROLOGICAL FACTORS
AU: KUTIEL,H, KAY,PA
NA: UNIV HAIFA,DEPT GEOG,IL-31905 HAIFA,ISRAEL
UNIV WATERLOO,DEPT ENVIRONM & RESOURCE STUDIES,WATERLOO N2L
3G1,ONTARIO,CANADA
JN: THEORETICAL AND APPLIED CLIMATOLOGY, 1992, Vol.46, No.2-3,
pp.99-108
IS: 0177-798X
DT: Article
AB: Recent variations in atmospheric circulation in the eastern
Mediterranean are analyzed and discussed. Interdecadal
differences in mean monthly 700 hPa geopotential heights for
June, July, and August in the period 1951-1980 show a trend of
decreasing pressure of the subtropical high pressure belt over
the Sahara Desert. The decrease is observed in the magnitude of
the high pressure, in its areal extent, and in its northward
position. Broader variations in other meteorological variables,
such as rainfall regimes, temperature fields, wind variability,
and evapotranspiration rates, are discussed in relation to
variations in pressure fields and in indices of circulation
such as the North Atlantic Oscillation. The trend from the
1950s through the 1970s was towards more temperate summer
climate in the region.
KP: AIR-TEMPERATURE VARIATIONS, NORTH-ATLANTIC OSCILLATION, SEA-
LEVEL PRESSURE, PRECIPITATION PATTERNS, SPATIAL-DISTRIBUTION,
RAINFALL VARIATIONS, MEDITERRANEAN AREA, GALILEE ISRAEL,
VARIABILITY, HEMISPHERE
(177) TI: LONG-TERM CHANGES IN THE GEORGES BANK FOOD WEB - TRENDS IN
STABLE ISOTOPIC COMPOSITIONS OF FISH SCALES
AU: WAINRIGHT,SC, FOGARTY,MJ, GREENFIELD,RC, FRY,B
NA: MARINE BIOL LAB,CTR ECOSYST,WOODS HOLE,MA,02543
NOAA,NATL MARINE FISHERIES SERV,NE FISHERIES CTR,WOODS
HOLE,MA,02543
JN: MARINE BIOLOGY, 1993, Vol.115, No.3, pp.481-493
IS: 0025-3162
DT: Article
AB: Fish scales from seven species of demersal fish in an archival
collection were analyzed for stable isotopic compositions of
carbon and nitrogen to study long-term changes in trophic
structure of the Georges Bank food web. Nitrogen isotopic
compositions are often used to infer trophic level. In the case
of haddock, Melanogrammus aeglefinus (Linnaeus), there was a
trend towards feeding at 2/3 of one trophic level (2.45 parts
per thousand in deltaN-15) lower in 1987 than in 1929. Values
of deltaC-13, frequently employed to identify sources of
organic carbon to consumers, declined by 1.5 parts per thousand
from 1929 to 1960, and then increased again toward the present,
suggesting changes in the food web at the level of the primary
producers. Superimposed on long-term isotopic trends were
short-term variations (1 to 10 yr). To identify potential
causes for these isotopic trends, canonical correlation
analysis was performed between isotopic data and a suite of
environmental and population factors including sea surface
temperature, the Greenland Regional Pressure Anomaly (GRPA),
the North Atlantic Oscillation (NAO), and the following haddock
stock parameters; stock size, fishing mortality, recruitment,
and weight-at-age-2 (a measure of growth rate). Isotopic
variation was significantly correlated with a combination of
environmental and population variables: GRPA, NAO, weight-at-
age-2, stock size, and fishing mortality. On the basis of
published gut content analyses, the seven fish species were
predicted to vary in trophic level (TL) from American plaice,
Hippoglossoides platessoides Fabricius), (TL 2.9) to summer
flounder, Paralichthys dentatus (Linnaeus), (TL 4.5), whereas
measured deltaN-15 values suggested smaller differences in the
trophic levels of these species (less than one TL). Four
species showed good agreement between gut-predicted and
measured deltaN-15 values, while three species did not.
Inclusion of information on ontogenetic dietary shifts in our
predictions improved the agreement in some cases but not in
others. Differences between stable isotope analysis and gut
content analysis in terms of what they measure, i.e.,
integrated assimilated diet vs short-term ingested diet,
respectively, may account for some of the differences in
results. Based on our analyses and previous studies, feeding
habits of these fish may undergo considerable year-to-year and
geographic variation, some of which may have been missed in
gut-content analyses. To the extent that these fish are
representative members of the food web, trophic variation in
these fish may indicate more general changes in the food web.
KP: CONTINENTAL-SHELF, TROPHIC DYNAMICS, CARBON, ATLANTIC, SEA,
FRACTIONATION, PLANKTON, RESUSPENSION, ZOOPLANKTON, C-13/C-12
(178) TI: ROLE OF THE ASIAN MONSOON ON THE INTERANNUAL VARIABILITY OF THE
GLOBAL CLIMATE SYSTEM
AU: YASUNARI,T, SEKI,Y
NA: UNIV TSUKUBA,INST GEOSCI,TSUKUBA,IBARAKI 305,JAPAN
JN: JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN, 1992, Vol.70,
No.1B, pp.177-189
IS: 0026-1165
DT: Article
AB: The role of the Asian summer monsoon on the interannual
variability of the global climate system particularly relevant
to the ENSO time scales is discussed, by examining the
statistical and dynamical links between the Asian summer
monsoon, the atmosphere/ocean system in the tropics and the
westerly flow regimes in the extratropics.
The Asian monsoon, the ocean and the atmosphere in the tropical
Pacific are tightly linked together as one climate system,
named here as the MAOS (Monsoon and the Coupled
Atmosphere/Ocean System). The MAOS prominently shows the
biennial oscillatory nature which tends to have anomalous
states starting in the northern summer monsoon season and
persisting for about one year (Yasunari, 1990a: 1991).
The anomalous state of the MAOS produces the anomalous
atmospheric circulation over the subtropics and the
extratropics of the north Pacific during summer through the
early winter, through the modulation of the subtropical high
and the stationary Rossby wave propagation mechanism. In the
mid winter, this anomalous circulation over the north Pacific
is evolved to the hemispheric winter anomalous circulation with
wavenumber-one and/or-two structure.
The anomalous circulation over Eurasia associated with this
hemispheric anomalous flow regime seems to provide a favorable
condition for the extensive (or diminished) snow cover area
over central Asia, which in turn is responsible for the
reversed anomalous state of the next Asian summer monsoon and
the MAOS. That is, the biennial nature of the climate system in
the northern hemisphere may be due, at least partly, to this
two-way interactions between the tropics and the extratropics.
In these processes, the Asian monsoon plays a key role as a
transmitter of climate signals between the tropics and the
extratropics through the land/atmosphere/ocean interaction in
the seasonal cycle.
In addition, it is strongly suggested that the North Atlantic
Oscillation (NAO), in reality, plays a crucial role in the
timing of the occurrence of the ENSO event, by stochastically
amplifying or damping the biennial oscillation of this coupled
climate system. That is, the more or less irregular ENSO cycle
may result from this interaction between the MAOS and the NAO,
where the former seems to have the nature of an almost-
intransitive climate system, while the latter seems to
represent the more chaotic nature of the westerly flow regime.
(179) TI: SIMULATION OF THE NORTH-ATLANTIC OSCILLATION IN A GENERAL-
CIRCULATION MODEL
AU: PITTALWALA,II, HAMEED,S
NA: SUNY STONY BROOK,INST TERR & PLANETARY ATMOSPHER,STONY
BROOK,NY,11794
JN: GEOPHYSICAL RESEARCH LETTERS, 1991, Vol.18, No.5, pp.841-844
IS: 0094-8276
DT: Article
AB: The year to year variations of winter climate of the North
Atlantic region including Northern Europe, Northwest Africa,
and North America are largely controlled by the phases of the
North Atlantic Oscillation (NAO). We have found that a coupled
ocean-atmosphere General Circulation Model simulates not only
the NAO, but its observed influences on precipitation in
northwest Africa, thereby showing that explanations of regional
scale climatic variations may be found through diagnoses of
such model simulations.
KP: SOUTHERN OSCILLATION, HEMISPHERE
(180) TI: PATTERNS OF LOW-FREQUENCY MONTHLY SEA-LEVEL PRESSURE
VARIABILITY (1899-1986) AND ASSOCIATED WAVE CYCLONE FREQUENCIES
AU: ROGERS,JC
NA: OHIO STATE UNIV,DEPT GEOG,103 BRICKER HALL,190 N OVAL
MALL,COLUMBUS,OH,43210
JN: JOURNAL OF CLIMATE, 1990, Vol.3, No.12, pp.1364-1379
IS: 0894-8755
DT: Article
AB: Spatial patterns of low-frequency sea level pressure (SLP)
variability are identified by performing rotated principal
component analysis (RPCA) on a long-term (1899-1986) Northern
Hemisphere gridded dataset. The analysis is limited to the
region 160-degrees-E eastward to 40-degrees-E due to missing
data early in the century. The objective is to identify a
comprehensive set of highly recurrent SLP teleconnection
patterns; to examine some aspects of their seasonality; and to
identify the associated mean winter pressure fields and cyclone
frequencies occurring at times of opposite eigenvector
polarity. The results are further described in the context of
the Southern Oscillation and known midtropospheric
teleconnection patterns.
Four low-frequency variability patterns are identified over the
Atlantic-European sector, including (i) the North Atlantic
Oscillation (NAO), and spatial patterns with SLP variability
centers over (ii) the eastern Atlantic (EATL), (iii) southern
Europe and the northern Mediterranean basin (SENA), and (iv)
Scandinavia (SCAN). The Pacific sector low-frequency
variability patterns include the (v) North Pacific Oscillation
(NPO), and patterns with centers over (vi) the north-central
Pacific (PAC) and (vii) the Bering Sea (BER). The EATL, SENA,
SCAN and BER patterns have not been identified in previous SLP
RPCA studies. Seasonal variations take place in the location of
the primary and secondary centers of SLP variability in each
teleconnection.
Each of the Atlantic teleconnections have at least one polarity
mode in which cyclones migrate toward Greenland and Iceland.
However, the opposite modes in the NAO and EATL are associated
with distinct zonally oriented cyclone tracks along latitudes
40-degrees-45-degrees-N. One mode of each Pacific pattern is
characterized by a zonally oriented cyclone track but the
opposite modes are characterized by cyclone maxima in the
eastern Pacific (NPO), the western Bering Sea (PAC) and another
track that turns northward toward the Bering Sea along the date
line (BER). The BER and PAC patterns closely resemble the
upper-air west Pacific and Pacific-North American patterns,
although the correlations between the RPCA scores and the
midtropospheric pattern indices can have small but significant
correlations to other midtropospheric patterns. The winter BER
scores are significantly lag correlated to the Southern
Oscillation index.
(181) TI: SPATIAL PATTERNS OF ATMOSPHERE OCEAN INTERACTION IN THE
NORTHERN WINTER
AU: WALLACE,JM, SMITH,C, JIANG,QR
NA: UNIV WASHINGTON,DEPT ATMOSPHER SCI AK40,SEATTLE,WA,98195
JN: JOURNAL OF CLIMATE, 1990, Vol.3, No.9, pp.990-998
IS: 0894-8755
DT: Article
AB: The variability of monthly mean sea-surface temperature (SST)
anomalies over the extratropical North Atlantic and Pacific and
its relation to atmospheric circulation anomalies over the
Northern Hemisphere during wintertime is investigated, by
applying eigenvector analysis to a 39-year dataset and
correlating the time series of the resulting expansion
coefficients with the hemispheric 500 mb height and sea-level
pressure fields.
In agreement with previous studies, the simultaneous
correlation between the time series of the expansion
coefficient of the first empirical orthogonal function (EOF 1)
of North Pacific sea surface temperature (SST) and the
hemispheric 500 mb height field resembles the Pacific/North
American pattern, and the corresponding pattern for Atlantic
SST resembles the North Atlantic Oscillation. In the vicinity
of the centers of action of these patterns, the SST
fluctuations associated with these modes explain on the order
of half the variance of 500 mb height and sligthly less of the
variance of the associated sea-level pressure fluctuations.
Analogous calculations were performed on the anomalous
midwinter SST tendency, defined as the SST anomalies averaged
from February through April minus the SST anomalies averaged
from October through December of the previous calender year.
The leading EOF's of SST tendency in both oceans exhibit
distinctive "sandwich" patterns, with bands anomalies of one
polarity over the western ocean centered near 30-degrees - 35-
degrees N, flanked by anomalies of the opposite polarity over
the northern oceans near 50-degrees N and in the subtropics,
near 15-degrees N. EOF 1 of North Atlantic SST tendency is more
robust than its counterpart for SST itself. The correlation
between the time series of the expansion coefficient of EOF 1
of North Pacific SST tendency and the hemispheric 500 mb height
field resembles the western Pacific pattern, and the
corresponding pattern for Atlantic SST resembles the western
Atlantic pattern, as defined by Wallace and Gutzler. "High
zonal index" atmospheric circulation patterns in winter [i.e.,
strong anticyclones near 30-degrees N, strong westerlies along
50-degrees N, and strong tradewinds] are observed in
association with anomalous warming of the ocean in the
anticyclone belt and cooling in the westerly and tradewind
belts. It is suggested that these patterns are particularly
effective in modulating the fluxes of latent and sensible heat
at the air-sea interface and wind-driven vertical mixing and
entrainment through their influence upon surface wind speed.
(182) TI: NORTH-ATLANTIC OSCILLATION - CONCEPT AND AN APPLICATION
AU: LAMB,PJ, PEPPLER,RA
NA: ILLINOIS STATE WATER SURVEY,CLIMATE & METEOROL
SECT,CHAMPAIGN,IL,61820
UNIV ILLINOIS,DEPT ATMOSPHER SCI,URBANA,IL,61801
JN: BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY, 1987, Vol.68,
No.10, pp.1218-1225
IS: 0003-0007
DT: Article
(183) TI: THE ASSOCIATION BETWEEN THE NORTH-ATLANTIC OSCILLATION AND THE
SOUTHERN OSCILLATION IN THE NORTHERN HEMISPHERE
AU: ROGERS,JC
NA: OHIO STATE UNIV,DEPT GEOG,COLUMBUS,OH,43210
JN: MONTHLY WEATHER REVIEW, 1984, Vol.112, No.10, pp.1999-2015
IS: 0027-0644
DT: Article
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