Potential Impacts of Soil Moisture on Monthly-Scale Precipitation During the Rainy Season in South China

Abstract

Land-atmosphere interactions provide a key pathway through which land-surface anomalies shape regional climate variability. Using ERA5 reanalysis data for 1985–2024, we examine the impacts of soil moisture on monthly precipitation during the rainy season in South China (SC) from both local and non-local perspectives. Singular value decomposition (SVD) and correlation-based diagnostics are combined to isolate coupled patterns and to trace their underlying physical processes. Enhanced soil moisture in July increases local evaporation and atmospheric humidity, thereby contributing to greater total rainfall. Concurrently, the augmented latent and sensible heat fluxes lower surface temperatures, reduce boundary layer depth, and boost convective available potential energy. The synergy between these favorable moisture and dynamic conditions underpins the positive soil moisture–precipitation feedback observed at a cross-monthly timescale. Beyond local feedbacks, anomalously wet soils over northern Indochina in July exert a robust positive influence on August rainfall in SC by modifying atmospheric circulation and moisture transport. A comprehensive synthesis indicates a synergistic effect between local soil moisture in SC and that in northern Indochina, collectively promoting increased precipitation in August. These findings shed light on the regional linkage mechanism of soil moisture–precipitation feedback across monthly scales, offering valuable insights for understanding the drivers of rainy-season precipitation in SC and improving short-term climate predictions.