Vertical motion in the Indian summer monsoon

Abstract

The vertical motion field in the Indian monsoon region has been studied for mean July, a strong monsoon day (7 July 1933) and a weak monsoon day (19 July 1963). We have used the quasi-geostrophic omega equation for this purpose, In addition to forcings due to thermal and differential voriticty advection, the vertical motion due to orography and friction have been included. The vertical motions due to the different forcing functions have been computed. The cumulative omega field due to all forcing functions and due to individual forcing functions together with their vertical profiles are delineated.

Conversion from potential to kinetic energy associated with the vertical circulations have been computed and presented in this paper, It is seen that the meridicnal circulation in the y-p plane is very marked on 7 July with ascent over north India and descent to the south. On 19th, however, uniform descent is seen everywhere. There is conversion from zonal available potential energy to zonal kinetic energy on the day of active monsoon. The conversion is much smaller on the day of weak monsoon. Other energy conversions are also discussed.