Characteristic and factors of stable isotope in precipitation in the source region of the Yangtze River

Abstract

This study aimed to systematically analyze the characteristic and factors of stable isotope in atmospheric circulation through a fixed-point sampling from April 1, 2016 to October 31, 2018 in the source area of the Yangtze River. The results showed that δ18O and δD were gradually changed to positive values from the outlet to the source area. With the increase in precipitation, the sub-cloud evaporation decreased in a negative exponential function. δ18O in the regions affected by the water vapor sources of the southeastern monsoon were higher than in other regions, and δ18O in the regions mainly affected by the westerly circulation were lower than those in the southeast coast of China. The average evaporation rates of falling raindrops (f) in ZMD, QML, and TTH were 9.53%, 13.14%, and 22.60%, respectively, whereas the average enrichment rates (E) were 10.32%, 15.95%, and 26.30%. Westerly circulation was a long-distance and high airflow, it had significant effects on the atmospheric precipitation in the whole source area of the Yangtze River. The southwest monsoon circulation from the Indian Ocean had also affected the atmospheric precipitation in TTH. However, the monsoon circulation only affected QML in summer, while it only affected ZMD in June and July.