Importance of Diabatic Heating for the Eastward-Moving Heavy Rainfall Events along the Yangtze River, China

Abstract

This study highlights the importance of the diabatic process in the heavy rainfall events (HREs) that are initiated on the eastern slope of the Tibetan Plateau and move to the lower reaches of the Yangtze River basin. These HREs, which cause significant socioeconomic losses in the Yangtze River basin, are typically maintained for 3 days. They develop when a large amount of moisture converges on the eastern slope of the Tibetan Plateau. By solving the quasigeostrophic (QG) omega equation, it is revealed that the vertical motion of HREs is organized by both dynamic and diabatic forcings, with the latter being dominant. The stationary boundary forcing on the eastern slope of the Tibetan Plateau also contributes to the initial organization of the HREs. While the dynamic vertical motion does not change much and the boundary forcing becomes negligible after the initial organization, diabatic vertical motion becomes more dominant in QG vertical motion (similar to 80%) as HREs develop and move downstream. The potential vorticity (PV) tendency budget analysis reveals that the development and eastward movement of the HRE-related surface cyclone is primarily associated with diabatic PV production to the east of the cyclone where a large amount of moisture converges. This result implies that the long-traveling HREs along the Yangtze River basin are highly self-maintaining in nature.