Dynamics of Persistence in Flash and Traditional Droughts across Homogeneous Rainfall Regions of India

Flash agricultural droughts (FDs) are defined based on the quick depletion of the crop root zone soil moisture (RZSM) which can have wide negative implications on the agricultural yield loss and associated sectors. FDs can be the sub-set of the traditional slow-developing agricultural droughts. The current study has investigated this intricate underlying interconnection over different HRRs in India for the period of 40 years (1981-2020). Traditional agricultural droughts are characterized using the monthly Standardized Soil Moisture Index (SSMI-1) and FDs using the Standardized Anomaly of the Pentad Root Zone Soil Moisture (SASM). Further, the long-term and short-term persistence is analyzed using the MF-DFA (Multifractal Detrended Fluctuation Analysis) based Hurst index approach in both time series data of flash and traditional droughts indices which has discovered the persistence information in the flash and traditional droughts. The results of the current study have inferred that FDs have long-term persistence (LTP) in humid regions, whereas short-term persistence (STP) is characteristic of traditional droughts in the same region. For the arid and semi-arid climate, the case is reversed with FDs having the STP and traditional droughts having the LTP during the studied period of 40 years. The results of the current analysis show that the persistence in the flash and traditional droughts has a synchrony with the background climate of different HRRs of India, which highlights the varying vulnerability for both types (flash and seasonal) of droughts.