Distant effects of monsoon depressions on weather over west Rajasthan

Abstract

Monsoon depressions are generally responsible for increased rainfall activity over northern and central parts of India during southwest monsoon season. That they also have some influence on the weather over places at quite some distance from the depression has been studied by some workers. One such effect mentioned by K.L. Sinha is that whenever monsoon depressions/lows form in the Bay of Bengal or interior and move in a westnorthwesterly direction, rain or thundershowers Occur over Jodhpur. This phenomenon of distant effects of monsoon depression on weather over west Rajasthan has been studied for the 20-year period from 1956 to 1975. It is seen that on 70% of the occasions when monsoon depressions/lows formed in the northwest Bay and crossed the Orissa coast, distribution and activity of rainfall over west Rajasthan showed a prominent increase.

An explanation for the phenomenon has been offered in this study in terms of soutl1ward shift of the mid-tropospheric trough line. Those occasions when the depressions/lows were over or near west Rajasthan have been excluded in the study.