Abstract: The water vapor sources of summer precipitation over west China (Urumqi, Qilian and Madoi) and east China (Changsha and Guangzhou) were analyzed by the backward trajectory calculation module and concentration weighted trajectory (CWT) of TrajStat software and combined with water vapor flux. The results showed that: ① Summer precipitation in Urumqi, Qilian and Madoi was significantly affected by the westerly water vapor, that in Changsha by the Western Pacific water vapor, and that in Guangzhou by the Indian Ocean water vapor; ② Locally recycled water vapor participated in summer precipitation over 5 sampling sites. The recycled water vapor affecting summer precipitation in west China was mainly distributed in the mountainous areas and basins where the relative humidity was high and the areas where the evaporation capacity was high. In east China, however, the recycled water vapor affecting summer precipitation was mainly distributed in the places where the surface waters are concentrative; ③ Over west China, the change of d value of water vapor in airmass was affected by both evaporation and underlying surface in the process of water vapor movement. Over east China, however, it was generally affected by evaporation only.

Key words: summer precipitation, backward trajectory, (concentration weighted trajectory)CWT, water vapor source, water vapor transport, China