羊卓雍错流域降水中稳定氧同位素变化特征

Variations of Stable Oxygen Isotope in Precipitation in the Basin of Yamzho Lake

根据青藏高原南部羊卓雍错流域白地、翁果和堆乡3个水文站2004年1～10月降水中δ18O的测定结果，分析了该流域降水中δ18O的变化特征及其与温度和降水量之间的关系．结果表明：3个站点降水中δ18O的值在雨季前变化不大，且都保持相对高值；进入雨季后都开始下降，雨季结束后又均开始增大．该流域夏季降水中δ18O表现出低值的特征与夏季西南季风的强烈活动密切相关．受西南季风影响，3个站点夏季降水均表现出季风降水的特征，降水中δ18O与降水时温度关系不明显，而与降水量之间存在着一定的反向变化趋势，从而表现出一定的“降水量效应”．羊卓雍错流域降水中δ18O的这种变化特征与拉萨的基本一致．

In this paper, the variations of δ18O of precipitation and the relationships between δ18O in precipitation and temperature and precipitation amount are analyzed by using the meteorological data observed in the summer of 2004 at Baidi, Wengguo and Duixiang Hydrographic Stations around the Yamzho Lake on the Tibetan Plateau. Precipitations at the three stations almost exhibit the same changing trend, showing a notable seasonal variation. Moreover, most of the precipitation events occur in summer, especially from June to September. The δ18O values in precipitation at the three stations also exhibit the same changing trend and they are high before the southwest monsoon onset, but begin to decrease when the southwest monsoon onset and then increase after the southwest monsoon retreat. The characteristic of low δ18O values in precipitation at the three stations correlates with southwest monsoon activity in summer. Affected by the southwest monsoon, the relationships between δ18O in precipitation and temperature are poor, It is found that the more precipitation amount is, the more depleted the δ18O is, which can be described as a precipitation amount effect that results in a poor δ18O-T relationship. The variations of δ18O in precipitation around the Yamzho Lake are similar to those in Lhasa.