Can monsoon moisture arrive in the Qilian Mountains in summer?

The isotopic composition of precipitation has been measured in samples simultaneously collected during individual precipitation events at a high-altitude station (Hulugou at 3260 m a.s.l.) in the middle Qilian Mountains, northwestern China. The observed changes of δ18O (δD) and deuterium excess with surface air temperature, precipitation and season have been evaluated to derive information on water vapor sources and the effects from monsoon moisture. The results indicated monsoonal moisture can arrive in the Qilian Mountains in summer, as indicated by: (1) under temperatures between 8 °C and 15 °C, the precipitation events are characterized by the decrease of δ18O and d excess owing to the influence from monsoonal moisture; (2) δ18O and δD showed statistically negative correlation with precipitation, which reflected the amount effect in at precipitation events scale; (3) not only the water vapor transporting vector but also composite circulation maps verified the arrival of monsoonal moisture in summer along the eastern margin of the Tibetan Plateau, which made a great contribution to regional precipitation under climate warming.