青藏高原中部降水稳定同位素变化与季风活动

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

根据1998年夏季中日GAME/Tibet项目在青藏高原中部进行的降水中稳定同位素研究结果以及相关的气象观测资料,分析了青藏高原中部夏季降水中δ18O的变化规律。研究结果发现,青藏高原中部夏季降水中δ18O的波动与大规模天气活动有关,而不是地方性的气象条件。该地区降水中δ18O对水汽来源的变化以及水汽的输送过程十分敏感。夏季伴随西南季风进入高原南部的水汽形成的降水中δ18O较低,而且季风活动越强,降水中δ18O也越低。从青藏高原北部而来的水汽或地方蒸发水汽形成的降水,其δ18O值较高。

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.