The North Atlantic Oscillation

Acknowledgements
Thanks for help from the following colleagues:

Some important NAO questions …
What exactly is it ?
What makes it tick ?
How well can it be forecast ?
How does it affect things ?

What should we call it ?
Druck Schwankungen
Northern Oscillation
North Atlantic Oscillation
Arctic Oscillation
Annular mode
Not the Arctic Oscillation
Al Moubarak
El Nao
Le YoYo Meteo
Northern Wazaaaaaa !

"“The relationships between weather..."
      “The relationships between weather over the Earth are so complex that it seems useless to try to derive them from theoretical considerations; and the only hope at present is that of ascertaining the facts and of arranging them in such a way that interpretation shall be possible.” (1908)

Early history of NAO research …
Saabye 1770-8
Teisserence de Bort 1883
Hann 1890
Hildebrandsson 1897
Meinardus 1898
Pettersson 1905
Exner 19??
Walker 1908, 1924, 1932
Defant 1924
Loewe 1937
Van Loon and Rogers 1978
+ many others …

NAO related publications
1980-2000

Wintertime SLP Variability
SLP Anomalies Dec/Jan/Feb (1988-1997)

Positive Phase of the NAO

 Negative phase of the NAO

  What is NAO ?

  NAO Indices

NAO varies on all time scales …

Power spectrum of daily NAO 1948-2000

What makes it tick …
Tropospheric processes ?
Stratospheric processes ?
Oceanic processes ?
Coupled processes ?
Anthropogenic forcing ?

 North Atlantic trends

Is it a coupled process ?

Is it a coupled process ?

How well can we forecast it ?
NAO = some trends + a lot of noise
X(t) f(t) e(t)
Persistent trend part f(t) gives some skill.
Amount of skill depends on the lead time !
Even low skill may be very useful !
Impacts can lag NAO à e.g. wheat quality

Daily Values of the NAO Index

Persistence in the NAO Time Series

Persistence in daily NAO …

Some wise words …
“Those who have knowledge, do not predict,
  Those who predict,  do not have knowledge.”
Lao Tzu
Chinese philospher 604-531 B.C

How does it affect things ?
Surface conditions
Physical environment
Terrestrial ecosystems
Marine ecosystems
Human activities

Surface impacts of NAO …

NAO and the sex life of Scandinavian ungulates

Future events …
OA26.03 Climate Variability
“The Northern Oscillations: NAO and AO”
European Geophysical Society
XXVI General Assembly
25-30 March 2001 Nice, France
Deadline for abstracts 1 Dec 2000 !!!
More information: www.copernicus.org

  Consensus of specialists …