Aspects of the large-scale tropical atmospheric circulation

Abstract

An account is given of a number of recent studies with idealised models whose aim is to furtherunderstanding of the large-scale tropical atmospheric circulation. Initial-value integrations witha model with imposed heating are used to discuss aspects of the Asian summer monsoon,including constraints on cross-equatorial flow into the monsoon. The summer descent in theMediterranean region and on the eastern sides of the summer subtropical anticyclones are seento be associated with the monsoons to their east. An aqua-planet GCM is used to investigatethe relationship between simple SST distributions and tropical convection and circulation. Theexistence of strong equatorial convection and Hadley cells is found to depend sensitively onthe curvature of the meridional profile in SST. Zonally confined SST maxima produce convectivemaxima centred to the west and suppression of convection elsewhere. Strong equatorial zonalflow changes are found in some experiments and three mechanisms for producing these areinvestigated in a model with imposed heating.