Complex network theoretic assessment of precipitation-driven meteorological drought in India: Past and future

Spatiotemporal analysis of droughts is important especially for future climate scenarios. We use complex network theoretic measures to understand spatiotemporal properties of precipitation-driven meteorological drought across India in past and future climate scenarios. We construct drought networks using event synchronization (ES) for moderate and extreme drought conditions derived using Standardized Precipitation Index at an aggregated scale of 6 months (SPI-6). Network measures like degree, closeness, betweenness and directionality are used to understand spatiotemporal properties of drought events. ES-based networks can capture synchronous events and help in ascertaining drought propagation through different regions. This study provides insight into the structural properties of drought networks and how they change for projected climate regimes. We find drought hotspots as well as regions which are vulnerable to spatially separated drought events. In the past, regions in western India were vulnerable to extreme droughts propagating from other regions of the country. Use of complex networks also reveals changes in drought propagation directions in future climate scenarios. Furthermore, using centrality measures, we also identify regions which aid in drought propagation and act as pathways connecting drought hotspots. Thus, changes in structural and topological properties of complex networks can be used to understand the impact of climate change across regions.