Dominance of summer monsoon flash droughts in India

Flash droughts intensify rapidly after onset and cause short-term but devastating impacts on agriculture and the ecosystem. However, the drivers and characteristics of flash droughts in India have not been examined. Here we use a well-calibrated and evaluated variable infiltration capacity (VIC) hydrological model to simulate root-zone soil moisture to identify flash droughts in India for 1951-2018 period. We show that flash droughts predominantly occur during the monsoon (June to September) in India. More than 80% of the country-level flash droughts occurred during the monsoon season in India. Similarly, four out of six homogeneous precipitation regions experienced more droughts during the monsoon season than the non-monsoon season. The Himalayan and Peninsular regions experience more flash droughts during the non-monsoon season primarily due to precipitation caused by western disturbance and northeast monsoon. Long dry spell with significant negative anomalies of precipitation during the monsoon season and positive air temperature anomalies rapidly deplete soil moisture causing flash droughts. The major country-level flash droughts occurred during the monsoon season of 1979, 2001, 1958, and 1986. About 10%-15% of rice (Oryza sativa) and maize (Zea mays) grown area in each year is affected by flash droughts during the monsoon season in India. Flash droughts during the monsoon season in India can directly affect crop production and indirectly pose challenges for meeting increased irrigation water demands.