Potential Stratospheric Influences on the Decadal NAO Variability and the Role of the Lower Boundary Forcing
Abstract
During Northern Hemisphere winter, variations in the strength of the stratospheric polar vortex and in the North Atlantic Oscillation (NAO) are closely related. This relationship is manifested on the intra-annual, interannual and interdecadal time scale. There is increasing body of evidence that large variations in the strength of the stratospheric circulation descend to the lower most stratosphere and are followed by anomalous tropospheric weather regimes. Previous model studies suggest that a strengthening of the polar vortex in the lower stratosphere due to the increased greenhouse effect leads to a preferred occurrence of the positive phase of the NAO. However, there is still disagreement whether the stratospheric vortex is an essential component in a feedback loop involving the NAO, or simply responds to the NAO. We present an overview about the mechanisms of the troposphere-stratosphere coupling and the resulting opportunity for a downward dynamic influence. To address the role of changes in the stratospheric circulation on interdecadal changes in the tropospheric climate, the sensitivity of NAO response to the sea surface temperature distribution under 2xCO2 conditions is studied by performing experiments with the middle atmosphere version of the GISS GCM.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2002
- Bibcode:
- 2002AGUSMGC41A..01P
- Keywords:
-
- 3362 Stratosphere/troposphere interactions;
- 1610 Atmosphere (0315;
- 0325);
- 1620 Climate dynamics (3309)