Isotopic variation of evapotranspirating vapor from grassland in the middle of Tibetan Plateau

We present here daily variation of isotopic composition of evapotranspirating vapor from grassland at the middle of Tibetan Plateau during rainy season. The evapotranspirating water was directly collected from small soil chamber from 13 to 28 August 2004. The temporal isotopic variation in evapotranspirating vapor shows gradual increase with time due to evaporation from soil surface accompanied with fractionation while anticyclone was covered. In this period the isotopic variation of precipitation at the study site also shows same increasing trend, although there is no relationship during large-scale disturbance passed through the study area. This result indicates that most of the precipitating water seems to be supplied from recycling water between land-surface and atmosphere when wind flux into Tibetan Plateau is weak.