High-resolution modeling of terrestrial hydrological processes offers new opportunities to advance understanding of land-atmosphere (L-A) interactions. This study investigates the impact of soil lateral flow (LF) on heavy rainfall events in mountainous areas. We conducted convection-permitting (4-km), fully coupled WRF/WRF-Hydro simulations over eastern China for three summers (June-August). By comparing the standard WRF run without LF effect (WRF-S) and WRF-Hydro coupled run with LF process turned on (WRF-H), we analyzed 13 heavy rainfall events over southern Anhui mountainous (SAM) region to quantify the impacts of LF on land surface variables and to reveal the physical pathway through which lateral flow influences heavy rainfall. Based on the precipitation differences between WRF-H and WRF-S in the SAM region, events were categorized into seven positive and six negative-effect events. Composite analysis of positive-effect events reveals that LF initially increases soil moisture (SM), particularly in valley areas. This intensifies evapotranspiration (ET) and increases convective available potential energy (CAPE) through L–A interactions, demonstrating an LF-triggered “SM–ET–CAPE” pathway that enhances precipitation over SAM region. In contrast, negative-effect events are characterized by enhanced rainfall in the Yangtze Plain, where rainfall-induced suppression of ET reduces CAPE, thereby inhibiting the pathway toward SAM region. This research contributes to a better understanding of L-A interactions, particularly the effects of LF on heavy rainfall in the SAM region.

• Lateral flow,WRF-Hydro,soil moisture,land-atmosphere interactions