Researchers Propose Copula-based Framework to Quantify Intensity of Compound Droughts

Global climate change is fueling increasingly frequent, complex, and severe drought events. However, precisely measuring the combined intensity of these "compound droughts" has long been a challenge.

To address this challenge, a research team led by Prof. YU Yang from the Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences, developed a multi-dimensional Copula-based framework to explicitly capture the nonlinear dependence among drought variables. Based on this framework, the researchers constructed a Standardized Compound Drought Severity (SCDS) index for the probabilistic quantification of compound drought intensity.

By integrating both bivariate and trivariate Copula structures, the framework effectively characterizes the coupled behavior of meteorological drought (MD), hydrological drought (HD), and ecological drought (ED). The findings showed that the SCDS index’s three-dimensional spatial distribution closely mirrors the patterns observed in individual drought indices. Crucially, its temporal variation demonstrated a high consistency rate of 83.5%, underscoring the index's robustness in tracking the dynamics of compound drought.

The study further revealed a significant downward trend in the SCDS index between 1987 and 2020, pointing to a progressive intensification of compound droughts in Xinjiang, China. A notable finding is that over half of the detected critical transition periods in drought intensification occurred between 2000 and 2005, suggesting this five-year span was a pivotal stage for regional drought exacerbation.

In addition, the researchers illuminated distinct seasonal shifts in the relative contributions of different drought types. Meteorological drought was found to dominate during spring, ecological drought took precedence in summer and autumn, and hydrological drought's influence grew more pronounced in winter.

“Our framework advances the quantitative understanding of the interactions among multiple drought types and provides an integrated tool vital for drought monitoring, risk assessment, and climate adaptation strategies,” said Prof. YU Yang, corresponding author of the study.

Read the full article: https://doi.org/10.1016/j.agwat.2026.110298

Contact

LONG Huaping

Xinjiang Institute of Ecology and Geography

E-mail: longhp@ms.xjb.ac.cn

Web: http://english.egi.cas.cn