On the role of large scale energetics in the onset and maintenance of summer monsoon -I: Moisture budget

Abstract

The effect of large scale moisture and moist static energy (MSE) budget on the onset and activities of summer monsoon is investigated. The data base for this study consists of twice daily First GARP Global Experiment (FGGE) level IIIb analysis of temperature, relative humidity, geopotential and wind fields for a tropical belt from 20 deg. S to 40 deg. Nand 0 deg. E to 150 deg. E, during May-July 1979.

The daily variation, vertical distribution and period averages of the various terms in latent heat energy (LHE) and MSE budget equation are closely examined to find out their influence on the activities of monsoon. The study indicates significant increase in the net LHE, horizontal. Convergence of moisture and diabatic moisture sink (indicator of excess condensation than evaporation) about two week before the onset pf monsoon over Kerala coast. Further, a decreasing trend is observed in horizontal convergence of moisture and moisture sink about one week before the break monsoon condition, which started over India on 16 July 1979. However, the various terms of the MSE budget equation do not depict my significant trend with the advance of the monsoon. The vertical distribution, period averages and the boundary fluxes also confirm the above findings.