Circulation over India and neighbourhood during the Southwest Monsoon season

Abstract

A survey has been made of circulation over India and neighbourhood as represented by streamlines analysis by different authors for July and of the theories put forward by different workers about the southwest monsoon taking into consideration the 1IOE observations over the Arabian Sea and facts of weather, climatology and orographic features of the country, It is shown that the claims of the exponents of streamlines analysis regarding its utility in day-to-day forecasting have to be treated with considerable reserve as the same does not give adequate importance to topographical features which playa vital role in the (a) production of rainfall besides convergence and up glide action, (b) modification of the properties of the air masses involved and (c) deflection of the air streams which contributes significantly in making the Indian southwest monsoon a selfsustatining system in the lower levels of the atmosphere, The significant layers would appear to be from the surface up to about 500 mb the position of the partition of the partition at 9 and 12 km between the middle latitudes, westerlies and the easterlies to their south remams about the same in the July "mean" and “active” and 'break" monsoon  conditions.