Changes in drought characteristics based on rainfall pattern drought index and the CMIP6 multi-model ensemble

Abstract

Drought monitoring and understanding of spatiotemporal patterns of drought characteristics are beneficial for sustainable agricultural water management at a regional scale. Changes in rainfall and drought patterns in future could impact decision-making in water resources allocation. The impacts of potential climate change on future meteorological droughts could be better analysed by utilizing an index that incorporates the number of rainy days information in addition to magnitude of rainfall to characterize the drought severity. In this study, we propose a bivariate copula-based multi-scalar rainfall pattern drought index (RPDI), a variant of the popular standardized precipitation index (SPI), and then the drought characteristics in India based on RPDI and SPI at different time scales (3-, 6- and 12-months) are analysed. When compared to RPDI, SPI underestimated drought severity and indicated low spatial heterogeneity of drought characteristics. The RPDI analysis identified changes in average drought severity and total number of drought events between two sample time slices (1920–1960 and 1961–2000) in the historical period. Future RPDI drought characteristics based on the coupled model intercomparison project phase 6 (CMIP6) multi-model ensemble under two emission scenarios known as shared socioeconomic pathways (SSPs): SSP126 and SSP245 are then computed. When drought characteristics in the near future (2020–2049) and far future (2070–2099) periods are compared with their baseline period (1985–2014) values, the results show that a significant declining trend is likely in the total number of drought events over the study region, while increases are projected in the maximum drought duration and maximum drought severity in future. Long-term drought characteristics extracted using 12-months scale RPDI, are likely to intensify in future under both scenarios. Considering the effects of erratic rainfall pattern on agricultural productivity, the RPDI drought monitoring framework could be utilized for efficient agricultural water management in future.