Flash droughts (FDs) are defined based on the quick depletion of the Root Zone Soil Moisture and can have a significant impact on the crop health of the region. The current study has defined the FD using the Standardized Change Anomaly of the Pentad Root Zone Soil Moisture (SASM) over the 40-year period (1981–2020) for the six Homogeneous Rainfall Regions (HRRs) of India. It is observed that the monsoon season is more vulnerable to the FD occurrence with NE (~ 11 events), WC (~ 11 events), and CNE (~ 10 events) regions having the higher frequency values. Areal extent of the FD events for different duration ranges infers that 84% of all India pixels experience the FDs having the average duration from 30 to 60 days over the past 40 years (1981–2020). The atmospheric drivers of the FDs are studied using the PCMCI (Peter and Clark’s Momentary Conditional Independence) causal algorithm. Precipitation (prcp), 2 m air temperature (t2m), vapour pressure deficit (VPD), net surface solar radiation (NSR), total cloud cover (TCC), and 2 m horizontal wind speed (u2m); all these variables are studied for their connection with the FD. It is observed that prcp is the dominant driver of the FD in India at both real and lag timestep. The strong coupling of TCC, NSR, and VPD is observed with the SM, followed by the prcp, in driving the FDs in real time. The current study is useful for the researchers, stakeholders, and policymakers for understanding the regional FD scenario of India in the baseline climatic settings.
Pachore et al. (Sun,) studied this question.