Abstract

The present study mainly focuses on heat and moisture budget components and its variations during meteorological drought conditions over India for the period, 1951-2013. The IITM sub-divisional summer monsoon standardised rainfall anomaly is considered to identify the meteorological drought, where the rainfall anomaly is less than one. From the analysis, thirteen meteorological droughts identified, and the rainfall decreased on spatial and temporal scales with significant changes in the frequency, duration and total amount of rainfall. In the lower levels, the westerlies are very weak where anti-cyclonic circulation is mainly observed along 60⁰-70⁰E. The intensity of easterly jet stream is decreased and further shifted towards south at 150 hPa level in drought years. Next, anomalous variations in relative humidity and vertical velocity induce the maximum reduction in the moisture amount (15%) in both lower and upper levels leads to weakening of local Hadley circulation strength. Next, the heat budget components are decreased over Bay of Bengal and coastal regions with a magnitude of 40 to 200 W/m² in drought years. It is observed that more moisture is transported to the equatorial region producing below average rainfall over the Indian subcontinent during weak monsoon periods. Hence, this study will help to identify the quantitative and qualitative estimation of drought conditions for long-range prediction of rainfall forecasting. 

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