The Zonal Symmetric Paradigm of the Northern Annular Mode and its Limits for the Understanding of Tropospheric Climate Variability
Abstract
The Northern Annular Mode (NAM) has been defined as the leading empirical orthogonal function of the monthly mean anomalies of the Northern Hemisphere sea-level pressure. This mode is characterized by a hemispheric scale seesaw of atmospheric mass between the high latitudes and parts of the mid-latitudes. During winter, the barotropic structure of the NAM in the troposphere extends up to the stratosphere. The structure of the NAM is virtually identical to that of the widely recognized Southern Hemisphere annular mode and it has been suggested that the zonal symmetric structure of these modes results from the inherent atmospheric dynamics. We discuss the limits of this zonal symmetric paradigm of hemispheric scale variability in the atmospheric dynamics for the understanding of tropospheric climate variability and climate change in the Northern Hemisphere 1) by comparing the spatial degrees of freedom of the horizontal circulation between troposphere and stratosphere, 2) by comparing characteristic features of the dynamic troposphere-stratosphere coupling between the Northern and Southern Hemispheres, and 3) by studying the response of the tropospheric circulation to the sea surface temperature distribution in the 2xCO2 climate.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2002
- Bibcode:
- 2002AGUSM.A22C..04P
- Keywords:
-
- 3362 Stratosphere/troposphere interactions;
- 1610 Atmosphere (0315;
- 0325);
- 1620 Climate dynamics (3309)