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The Arctic oscillation signature in the wintertime geopotential height and temperature fields

The Arctic oscillation signature in the wintertime geopotential height and temperature fields The leading empirical orthogonal function of the wintertime sea‐level pressure field is more strongly coupled to surface air temperature fluctuations over the Eurasian continent than the North Atlantic Oscillation (NAO). It resembles the NAO in many respects; but its primary center of action covers more of the Arctic, giving it a more zonally symmetric appearance. Coupled to strong fluctuations at the 50‐hPa level on the intraseasonal, interannual, and interdecadal time scales, this “Arctic Oscillation” (AO) can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft. It is proposed that the zonally asymmetric surface air temperature and mid‐tropospheric circulation anomalies observed in association with the AO may be secondary baroclinic features induced by the land‐sea contrasts. The same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature, sea‐level pressure, and 50‐hPa height over the past 30 years: parts of Eurasia have warmed by as much as several K, sea‐level pressure over parts of the Arctic has fallen by 4 hPa, and the core of the lower stratospheric polar vortex has cooled by several K. These trends can be interpreted as the development of a systematic bias in one of the atmosphere's dominant, naturally occurring modes of variability. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Geophysical Research Letters Wiley

The Arctic oscillation signature in the wintertime geopotential height and temperature fields

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References (35)

Publisher
Wiley
Copyright
© 1998 by the Chinese Geophysical Society
ISSN
0094-8276
eISSN
1944-8007
DOI
10.1029/98GL00950
Publisher site
See Article on Publisher Site

Abstract

The leading empirical orthogonal function of the wintertime sea‐level pressure field is more strongly coupled to surface air temperature fluctuations over the Eurasian continent than the North Atlantic Oscillation (NAO). It resembles the NAO in many respects; but its primary center of action covers more of the Arctic, giving it a more zonally symmetric appearance. Coupled to strong fluctuations at the 50‐hPa level on the intraseasonal, interannual, and interdecadal time scales, this “Arctic Oscillation” (AO) can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft. It is proposed that the zonally asymmetric surface air temperature and mid‐tropospheric circulation anomalies observed in association with the AO may be secondary baroclinic features induced by the land‐sea contrasts. The same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature, sea‐level pressure, and 50‐hPa height over the past 30 years: parts of Eurasia have warmed by as much as several K, sea‐level pressure over parts of the Arctic has fallen by 4 hPa, and the core of the lower stratospheric polar vortex has cooled by several K. These trends can be interpreted as the development of a systematic bias in one of the atmosphere's dominant, naturally occurring modes of variability.

Journal

Geophysical Research Letters – Wiley

Published: May 1, 1998

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