Spatiotemporal dependence of heavy precipitation on soil moisture anomalies in the Yangtze River Basin, China.

Abstract

Against the background of global warming, the drivers of heavy precipitation (HP) and flooding have become markedly more complex. Soil moisture (SM) not only contributes to flood generation but also influences the occurrence of HP through land-atmosphere feedback, underscoring its central role in predicting extreme events. In this study, precipitation intensity and frequency conditioned on antecedent SM states were quantitatively assessed utilizing a novel SM memory-based statistical framework. The results reveal that elevated antecedent SM conditions are strongly associated with intensified precipitation events in the Yangtze River Basin (YRB). Spatial analysis demonstrates that anomalies (SMA) in inland regions exert statistically significant preconditioning effect on HP. However, the triggering role of SMAs appears more dominant, with approximately 80 % of basin-wide HP events triggered by preceding SMAs. Notably, the triggering effect of SMA on HP has remained relatively stable at the decadal scale since the 1960s. However, their preconditioning effect has exhibited a weakening trend in recent years, likely linked to the declining in the frequency of SMA events. Furthermore, projected future scenarios indicate a basin-wide decline in both preconditioning and triggering effects of SMA on HP. The primary impact zones are projected to shift from inland regions to the more humid middle and lower reaches of the basin. The dependence of future HP events on SM conditions will decrease, with particularly pronounced weakening in SM-limited northern regions. This study offers insights into the investigation of SM-Precipitation interactions and their implications for risk management.