Soil Moisture Droughts under the Retrospective and Projected Climate in India

Abstract

hanges in precipitation, air temperature, and model-simulated soil moisture were examined for the observed (1950?2008) and projected (2010?99) climate for the sowing period of Kharif and Rabi [KHARIF_SOW (May?July) and RABI_SOW (October?December)] and the entire Kharif and Rabi [KHARIF (May?October) and RABI (October?April)] crop-growing periods in India. During the KHARIF_SOW and KHARIF periods, precipitation declined significantly in the Gangetic Plain, which in turn resulted in declines in soil moisture. Statistically significant warming trends were noticed as all-India-averaged air temperature increased by 0.40°, 0.90°, and 0.70°C in the KHARIF, RABI_SOW, and RABI periods, respectively, during 1950?2008. Frequency and areal extent of soil moisture?based droughts increased substantially during the latter half (1980?2008) of the observed period. Under the projected climate (2010?99), precipitation, air temperature, and soil moisture are projected to increase in all four crop-growing seasons. In the projected climate, all-India ensemble mean precipitation, air temperature, and soil moisture are projected to increase up to 39% (RABI_SOW period), 2.3°C, and 5.3%, respectively, in the crop-growing periods. While projected changes in air temperature are robust across India, robust increases in precipitation and soil moisture are projected to occur in the end-term (2070?99) climate. Frequency and areal extents of soil moisture?based severe, extreme, and exceptional droughts are projected to increase in the near- (2010?39) and midterm (2040?69) climate in the majority of crop-growing seasons in India. However, frequency and areal extent of droughts during the crop-growing period are projected to decline in the end-term climate in the entire crop-growing period because of projected increases in the monsoon season precipitation.