10.2
The short-term dynamic influence of the stratosphere on the troposphere during Northern Hemisphere winter
Judith Perlwitz, Columbia University and NASA/GISS, New York, NY
A downward influence from the stratosphere to the troposphere occurs by a downward propagation of zonal mean wind anomalies from the middle atmosphere into the troposphere due to wave-mean flow interaction. This leads to a change in the meridional wave propagation in the troposphere. To understand processes involved in this mechanism in more detail, a statistical-dynamic approach was applied to Northern Hemisphere observational data. This multivariate Single Wave Analysis (SWAN) is used to isolate - on a hemispheric scale - the vertical propagation of ultra-long spherical wave-like anomalies and the relationship between the strength of the stratospheric polar winter vortex and mid-tropospheric waves. The results show that a significant linear influence of the strength of the stratospheric polar vortex on the waves of zonal wave number (ZWN) 2 and 3 in the mid-troposphere exists. For waves of ZWN 1 nonlinear effects dominate because different propagation characteristics for these waves are observed under strong and weak polar vortex conditions. The results are used to evaluate atmospheric general circulation models.
Session 10, Stratosphere-Troposphere Interactions
Thursday, 7 June 2001, 2:00 PM-3:05 PM
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