The vertical slope of the monsoon trough and its association with distribution of rainfall over India

Abstract

By evaluating the Margules' simplified equation for the slope of a surface of airmass discontinuity with relevant data and comparing the computed slope with observations, it has been suggested that, to a high degree of approximation, the monsoon trough over India may be regarded as a surface of airmass discontinuity separating the relatively warm easterly winds in the north from the cool westerly winds in the south and sloping southward with height. Rainfall associated with the normal southward slope of the trough appears to be distributed mainly to the south of the MSL position of the trough. However, both the slope of the trough as well as the distribution of rainfall associated with it are found to undergo major changes when synoptic disturbances such as the Bay of Bengal depressions or western disturbances affect India. Some main patterns of these changes are identified and discussed with reference to the possible role of the synoptic disturbances.