Data analysis and numerical simulation of moisture source and transport associated with summer precipitation in the Yangtze River Valley over China

Abstract

In this study, the moisture source/sink and long-distance moisture transport associated with the summer precipitation in the mid-lower reaches of the Yangtze River Valley (YRV) over China have been investigated based on both data analysis and numerical simulations using the regional climate model RegCM3. The study focused on both a case of the 1998 summer flood events and the interannual variation of summer precipitation during 1961–2005 in the YRV. The results show that (1) the low latitudinal band from the Bay of Bengal, Indochina Peninsula, South China Sea to the Philippine Island is the major moisture source region for the summer precipitation in the YRV; (2) an eastward moisture transport from the Bay of Bengal and a westward moisture transport from the Philippines Sea meet at the South China Sea, where a main water vapor channel forms and advances north-northwestward and turns northeastward in the vicinity of the eastern Tibetan Plateau and South China to the YRV; and (3) the long-distance moisture transport from the eastern Indian Ocean-South China Sea to the YRV contributes to more than half of the summer precipitation in the YRV. Furthermore, it is shown that RegCM3 driven by the NCEP/NCAR reanalysis is able to reproduce the overall climatological water vapor transport in East Asia and the features of the water vapor flux for flooding and drought years in the YRV as well as simulate the YRV flood events in the summer of 1998 reasonably well.