Complex network-based analysis of the spatial evolution of the flash droughts over India

Flash droughts, characterized by a rapid decline in soil moisture, are short-term drying events that can cause significant damage to crops when they occur during the growing season. Understanding the spatial and temporal evolution properties of flash droughts is crucial for the effective mitigation and management of this extreme event. The present study employed the complex network theory to assess the spatio-temporal properties of the flash drought which was quantified using the soil moisture percentile drop (SMPD) based definition during the period from 1981 to 2020 over the entire Indian region. An event synchronization (ES)-based complex network is constructed and the spatial propagation of the flash droughts is analyzed using the unidirectional and directed complex networks-based metrics i.e., strength, direction, and distance. Initial results gave insights into how the flash drought hotspots are connected in space and their temporal evolution pattern. From the result of the distance metrics, it was observed that flash drought propagates for longer distances in the central-eastern and southern peninsular regions as compared to the rest of the regions over India. Inference gained from the present analysis can be useful for building an early warning system for flash drought in terms of onset and spatial propagation along with insights on the spatially connected flash drought vulnerable regions.