Inter-annual and seasonal variations of meteorological drought and their drivers in the southwest karst region of China

Revealing the spatial and temporal evolution characteristics of drought in the southwest karst region is vitally important for drought early warning and ecological environmental protection. In this paper, based on the standardized precipitation evapotranspiration index (SPEI) from 1902 to 2023, we analyzed the variations and influencing factors of interannual and seasonal meteorological drought by means of Theil-Sen median trend analysis, Mann–Kendall test, wavelet analysis, geodetector, and correlation analysis. Our results showed that (1) The interannual SPEI had a decreased trend with a rate of 0.029/10a, without mutation point and showing a no significant drying trend, and the seasonal SPEI also showed a decreasing trend, with a mutation point in autumn and decreasing significantly. Spatially, accounting for 78.29% and 84.31% of the regions exhibited a decreasing trend in annual and autumn. (2) The main cycles of drought were 55a, 37a, 25a, 12a, and 4a at the interannual scale, while the cycles varied from medium to long at the seasonal scale. (3) In different study periods, karst landform had the greatest influence on the spatial variability of drought, followed by climate factors, while topographic factors and land use change had relatively weak influence. The interaction between climate factors and karst landform could significantly enhance their explanatory power on the spatial variability of drought. (4) The NAO, ENSO3.4, AO, and IOD were the dominant influence factors for interannual and seasonal drought variability, and the influence with an obvious interannual transition. Multiple regression analysis illustrated the NAO, ENSO3.4, and IOD had an explanatory power of 15.9%, 12.2%, and 10.7% to drought variations at interannual scale, and the ENSO3.4, AO, and IOD had an explanatory power of 24.1%, 21.3%, and 14.7% to seasonal drought variations, respectively.