Stable isotope variation of precipitation in the middle of Qinghai Xizang Plateau and monsoon activity

The variation of δ18O of precipitation in the middle of Qinghai Xizang Plateau is analyzed based on the observation of stable isotope of precipitation in the summer of 1998 by GAME/Tibet. The results show that δ18O of precipitation in the middle of the plateau is controlled by large scale synoptic condition, rather than the local meteorological condition. The variation of δ18O of precipitation in the middle of the plateau in summer has close relation with the wind direction and wind intensity, revealing the strong impact of moisture origins on δ18O of precipitation. The moisture from south with the monsoon in the summer time is always related with very low δ18O of precipitation, and δ18O became extremely low when the monsoon activity became more intensive. Whereas moisture from north or from local evaporation is always characterized by very high δ18O of precipitation.