Dynamic compound droughts in the Contiguous United States

Ali Sarhadi, Reza Modarres, Sergio M. Vicente-Serrano

Severe meteorological and hydrological drought synergy contributes to adverse and large-scale social, economic, and environmental impacts beyond the individual occurrences. The risk, memory, and causality of this combination can be expressed by a compound dynamic perspective under a changing climate. In this study, we show that the concurrent risk of hydrological and metrological droughts has increased by up to 10% to 20% for moderate and severe events, and up to 8% to 12% for extreme events in recent decades, across watersheds in the western and southeastern Contiguous United States (CONUS).

A bivariate Generalized Autoregressive Conditional Heteroskedasticity (GARCH) model also indicates that the dynamic compound droughts have strong short-term memory based on co-volatility, especially in the western CONUS. The results also suggest a short-memory causative dynamic mechanism, through which meteorological droughts may exponentially increase the occurrence of long-lasting and severe compound droughts, especially in the western CONUS. Given the broad impacts of extreme compound droughts, our findings have critical relevance for the ongoing proactive and long-term adaptive plans to mitigate adverse consequences, especially in the western territories of the CONUS.

Ali Sarhadi, Reza Modarres, Sergio M. Vicente-Serrano, Dynamic compound droughts in the Contiguous United States, Journal of Hydrology, Volume 626, Part A, 2023, 130129, ISSN 0022-1694, https://doi.org/10.1016/j.jhydrol.2023.130129.