Observational Evidence for Multivariate Drought Hazard Amplifications Across Disparate Climate Regimes

Drought poses significant challenges to global water security in a warming world. A global-scale synthesis of the multivariate drought risk considering interdependencies between drought attributes across disparate climate regimes is still lacking. Leveraging precipitation and streamflow observations of 270 large catchments over the globe, we show that multivariate drought hazard amplifies significantly (at similar to 65-76% of catchments) considering dependence between drought duration and severity. A signifying nature of this amplification (A) is the power-law scaling with dependence metric (A proportional to tau(lambda);lambda=5-12; where tau and lambda are Kendall's correlation and the scaling exponent), revealing current approaches considering drought attributes as independent or linearly dependent will severely underestimate likelihood of extreme droughts. Furthermore, we find disparate responses in the multivariate imprints of meteorological to hydrological droughts across climate types, with strengths varying from large to modest in Tropics and Mid-latitudes, which indicates weaker overlap between rain-deficit and streamflow droughts. In contrast, a strong overlap in multivariate hazards of rain-deficit and streamflow droughts is apparent across transitional Subtropics. Our study highlights the relevance of accounting for multivariate aspects of drought hazards to inform adaptation to water scarcity in a changing climate.

Automated summary

Drought poses significant challenges to global water security in a warming world. A global-scale synthesis of the multivariate drought risk considering interdependencies between drought attributes across disparate climate regimes is still lacking. Our study shows that multivariate drought hazard amplifies significantly considering dependence between drought duration and severity. Furthermore, we find disparate responses in the multivariate imprints of meteorological to hydrological droughts across climate types. Our study highlights the relevance of accounting for multivariate aspects of drought hazards to inform adaptation to water scarcity.