Multi‐Scale Meteorological Drought Return Periods and Climatic Associations in the Guangxi Karst Region Based on SPEI and 3D C‐Vine Copula

Based on ERA5 reanalysis data (1940–2023), this study integrates trend tests, a three‐dimensional C‐vine Copula model, and cross‐wavelet analysis to assess multi‐scale meteorological drought in the Guangxi Karst Region, a typical humid subtropical karst ecosystem. Our results show that Guangxi exhibits an overall warming‐drying trend, with significant increases in drought duration, severity, and peak since the early 21st century; however, only continuous karst regions show a statistically significant warming‐drying trend. Drought risk is generally higher in karst regions than in non‐karst regions, with differences showing scale and return period dependence. The joint risk of 20‐year return period extreme drought follows a “low in the northeast, high in the southwest” spatial pattern. Extreme heat (TX90p) exhibits the strongest statistical association with annual‐scale drought, contributing more than consecutive dry days (CDD) and ENSO. While short‐ to medium‐term droughts have shown recent alleviation, annual‐scale drought has intensified persistently. These findings provide a scientific basis for refined drought risk management in humid subtropical karst regions.