GFI/BCCR Seminar: Monsoons: Structure, Variability, and Remote Influences

Prof Roberto Mechoso (UCLA, Los Angeles, US):

Monsoons: Structure, Variability, and Remote Influences

Abstract
After a brief overview of the monsoon systems of the world, the talk concentrates on the South American monsoon. For this system it is shown that the connection between precipitation variability over the eastern Brazil–SACZ convective margin and the intensity of the southeast trades is established through the ventilation mechanism as air from the ocean with low moist static energy is advected over the continent.

It is also shown that land surface processes in a coupled atmosphere-ocean general circulation model  can modify the seasonal cycle of sea surface temperatures in the equatorial Pacific, as well as the simulated ENSO frequency, amplitude, and locking to the seasonal cycle. It is argued that his impact is mainly from the tropical African continent, where convective heating anomalies associated with different land surface processes parameterizations can trigger global teleconnections through equatorial wave dynamics.

Finally, the presentations asks why the austral subtropical anticyclones are stronger in winter than in summer - unlike their boreal counterparts which are stronger in summer than in winter. It is concluded that this notable feature of the general circulation is due to the seasonal asymmetry in the interhemispheric effects of the summer monsoons.