NYCCS/ITPA-MSRC Seminar

Dargan Frierson

Department of Geophysical Sciences
University of Chicago,
Chicago, Illinois

“Tropical Circulations in a Hierarchy of Atmospheric Models”

Monday, February 19, 2007
Endeavour Hall, Room 120
10:00-11:15 AM

We investigate the large scale dynamics of the tropical atmosphere using a variety of atmospheric models, from the simple to the comprehensive. The primary model we use is an idealized moist GCM, with simplified physical parameterizations that isolate the effect of latent heat release on the general circulation. This model fills a largely unexplored piece of a model hierarchy, which allows for both clean tests of simple theories, and comparisons with full GCM’s. We use the model to investigate the dynamics of the Hadley circulation, ITCZ, and convectively coupled waves, comparing with atmosphere-only and fully coupled general circulation models. Our experiments with convection schemes classify the ways in which convection can influence the ITCZ and Hadley circulation, suggesting a mechanism of deep tropical control on the Hadley cell. The experiments with convectively coupled equatorial waves proposes and explains a simple way to slow down and/or intensify Kelvin waves, the MJO, and other tropical variability, which is tested and confirmed in a full GCM.