Desitiny of the moisture evaporated from the Yangtze River basin and its contribution to precipitation in downwind regions

The Yangtze River basin, situated along a pivotal East Asian monsoon pathway, is characterized by substantial evaporation and dynamic moisture transport processes. However, the destination of evaporated water vapor and its contribution to precipitation in downwind regions remain unclear. In this study, the ERA5 meteorological dataset, merged CN05.1 and GPCP V3.2 precipitation datasets, as well as merged GLEAM and OAFlux evaporation datasets, were utilized to drive the WAM-2layers model. This model was employed to track the destination of evaporated moisture from the entire Yangtze River basin, its upper reaches, and middle-lower reaches during 1984—2022, so as to quantify its contribution to precipitation in downwind regions. Results show that: ① Moisture from the Yangtze River basin mainly contributes precipitation to the basin itself, the Asian continental areas and adjacent oceanic regions to the northeast of the basin, and the northern Pacific. ② Precipitation recycling ratios for the entire basin, the upper reaches, and the middle-lower reaches are 12.18%, 14.72%, and 5.81%, respectively. ③ The impact on downwind precipitation exhibits distinct seasonal patterns: the contributions increase and the affected area expands during spring and summer, while the contributions decrease and the affected area contracts during autumn and winter. ④ The precipitation contribution shows a significant increasing trend in the Yangtze River source region, the lower reaches, the East China Sea, and parts of the western North Pacific. Regarding to transmission pathways and moisture sinks, the precipitation contribution from the Yangtze River basin demonstrates high interannual stability.