Decadal variability of precipitation and moisture source attribution over India

Abstract

AbstractThe seasonal variability of precipitation has a profound impact on water demand for India's agricultural and socio‐economic sectors which are associated with continental and surrounding oceanic moisture sources controlled by dynamic and thermodynamic processes. In this study, moisture sources have been tracked by the Lagrangian trajectory approach over four homogeneous regions: Northwest India (NWI), Central India (CEI), Northeast India (NEI) and South Peninsular India (SPI). ERA‐Interim reanalysis data are used throughout the study for three decades from 1989 to 2018. The results indicate that the multidecadal variability of precipitation has strengthened towards the mid‐decade (1999–2008), mainly attributable to moisture source transport from the Arabian Sea. These enhancement patterns of moisture sources have been widespread over Central India for all three decades. Moisture availability in the boundary layer highly affects the precipitation and it is found that 80% of the moisture above the boundary layer contributes >10% of monsoonal precipitation occurrences. Further, the NEI drying trend in monsoonal rainfall is found to be related to the consequent weakening of the land–ocean temperature gradient (LOTG) during all three decades in this region and the absence of low cloud cover over the region throughout the study period. In addition, the moisture sources are regulated by prevailing large‐scale features such as frequency of La Niña, northward shifting of low‐level jet and strengthening of Hadley cell.