Synoptic time-series surveys of precipitation δ18O and its relationship with moisture sources in Yunnan, southwest China

The stable oxygen isotopic composition (delta O-18) of different water bodies can provide valuable information for investigation of hydrological processes, and it is an effective natural tracer that can be used to characterize the moisture sources of precipitation. In this study, to analyze the influence of moisture sources and meteorological variables on variations of precipitation delta O-18, a project of monitoring intense precipitation events was conducted through three entire years (2009-2011) at the Kunming, Mengzi, and Tengchong stations in Yunnan Province, southwest China. The results suggested that variations of precipitation delta O-18 in Yunnan exhibit a significant seasonal variability. The use of high -resolution data revealed a significant anti-temperature effect as well as an amount effect. Additionally, we found that precipitation delta O-18 does not follow the amount effect during some rainfall events of two consecutive days. In detail, the first day has higher precipitation amount than the second day. However, the precipitation delta O-18 values of the second day are more negative than those from the first day. Significantly positive correlations between precipitation delta O-18 and wind speed at different pressure levels (800, 700, 500, and 300 hPa) demonstrate that wind speed is an important controlling factor of variations of precipitation delta O-18. Backward trajectory results generated by the HYSPLIT model show that the moisture sources for precipitation with low delta O-18 during the wet season are mainly from the Bay of Bengal (BoB), Arabian Sea (AS), and South China Sea (SCS). By comparison, the high delta O-18 values of precipitation during the dry season are found to correspond to remote westerly air masses and inland re-evaporated vapor. Moreover, the precipitation PO associated with typhoons is much lower than that of the normal precipitation events. These findings indicate that the stable isotopic composition of precipitation is closely related to meteorological variables and is rapidly responsive to changes in sources of moisture. (C) 2016 Elsevier Ltd and INQUA. All rights reserved.