Stable isotopes characteristics of precipitation over Shaanxi-Gansu-Ningxia and its water vapor sources.

Abstract

Based on hydrogen and oxygen stable isotopes in precipitation and meteorological data over Shaanxi-Gansu-Ningxia provided by the Global Network of Isotopes in Precipitation (GNIP) and in previous literature, the spatial and temporal variations of oxygen stable isotopes in precipitation and their driving factors were analyzed, the local meteoric water line (LMWL) functions were established. The results showed that the slope and intercept of the LMWL changed in the order of Gansu<Shaanxi<Ningxia, with all of them being lower than slope and intercept of the Global Meteo-ric Water Line. The precipitation process of three provinces had been evaporated and fractionated to different degrees. The evaporation was enhanced along Ningxia, Shaanxi and Gansu. The δ18O value in precipitation in the Shaanxi-Gansu-Ningxia region was enriched in summer and autumn but poor in winter and spring. For the spatial distribution, the weighted δ18O value decreased from the northwest to the southeast. δ18O in precipitation showed significant temperature effect, but was no precipi-tation effect, reflecting the characteristics of continental climate in the middle and high latitudes. The quantitative relation of elevation effect was -0.12‰·(100 m)-1, and latitude effect was more significant by -0.27‰ per °. The water vapor source was tracked by HYSPLIT model. The cluster trajectory of air masses showed that water vapor from the Bay of Bengal, southeast monsoon and westerly zone were the main sources in summer half year, while it mainly transported by the westerly belt in winter half year.