Stable isotope variations in precipitation over Deqin on the southeastern margin of the Tibetan Plateau during different seasons related to various meteorological factors and moisture sources

Abstract

This study investigated the variations of stable isotopes (δ18O and δD) in precipitation at Deqin on the southeastern margin of the Tibetan Plateau. The results show that correlations between stable isotopes in precipitation and temperature vary during different seasons. In comparison, an apparent inverse correlation between stable isotopes and precipitation amount exists throughout different seasons. Hence, the “amount effect” appears to have significantly controlled the stable isotope variations in precipitation over the entire sampling period, rather than the “temperature effect”. The overall temporal variations of δ18O and δD in precipitation from Deqin are similar to those from a southern station at Xishuangbanna. Both stations demonstrate considerably depleted precipitation δ18O values in the summer as a consequence of intense Asian summer monsoon activities. However, at Xishuangbanna, the occurrences of the timing and duration of the depleted δ18O values, as well as the negative surface lift index values, occur earlier and last longer than those at Deqin. These results indicate that the Asian summer monsoon onset is later and that the duration of the monsoon activities is shorter at Deqin relative to Xishuangbanna.