Seasonal variations in drought drivers and assessment in Henan's vegetated regions

Drought poses a severe threat to agricultural production, ecological environments, and socioeconomic stability. To address the insufficient research on drought mechanisms in vegetated areas and the challenges in disaster prediction, this study focuses on Henan Province, examining the multi-scale driving mechanisms and precise assessment of drought in vegetated regions. The Palmer Drought Severity Index (PDSI) was selected as the quantitative metric for drought severity. Meteorological factors—precipitation, temperature, and evapotranspiration—were incorporated, while the Normalized Difference Vegetation Index (NDVI) was used to delineate vegetation-dominated arid and non-arid zones. Based on multisource data from 2019 to 2023, XGBOOST+SHAP and logistic regression models were constructed for analysis. SHAP was employed to quantify the contribution weights of each factor to drought, revealing seasonal-scale driving mechanisms: In the second and third quarters, high temperatures intensified evapotranspiration, with precipitation replenishment becoming the primary cause of drought. By the fourth quarter, evapotranspiration replaced temperature as the core influencing factor. Logistic regression was applied to normalize data from 2019 to 2022, and the results were validated using 2023 data. The model achieved quarterly fitting accuracy above 0.85 and correctness exceeding 0.9, confirming its universality and applicability. This study clarifies the evolution characteristics of drought in Henan Province: drought gradually spreads from the central-western to northern regions with seasonal shifts before transitioning southward. Severe droughts occur in western and northern Henan, while eastern and southern Henan often experience seasonal droughts. Based on these findings, the study provides scientific support for vegetation drought monitoring and early warning, disaster prevention and mitigation, and regional sustainable development in Henan Province.