Acta Geographica Sinica ›› 2008, Vol. 63 ›› Issue (1): 12-22.doi: 10.11821/xb200801002

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Characteristics of δ18O in Precipitation over Northwest China and Its Water Vapor Sources

LIU Jianrong1,2, SONG Xianfang1, YUAN Guofu3, SUN Xiaomin3, LIU Xin1,2, CHEN Feng2,4, WANG Zhimin1, WANG Shiqin1,2   

  1. 1. Key Laboratory of Water Cycle & Related Surface Process, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    2. Graduate University of the Chinese Academy of Sciences, Beijing 100039, China;
    3. CERN Sub-center of Water, Beijing 100101, China;
    4. Institute of Atmospheric Physics, CAS, Beijing 100029, China
  • Received:2007-08-28 Revised:2007-11-25 Online:2008-01-25 Published:2008-01-25
  • Supported by:

    National Natural Science Foundation of China, No.40671034; Foundation for Environment Field Stations Research of CAS, Program for Isotopes in Precipitation of Chinese Ecosystem Research Network


In order to reveal the characteristics and climatic controls on the stable isotope composition in precipitation over Northwest China, seven stations have been selected from the Chinese Network of Isotopes in Precipitation (CHNIP). During the year 2005, monthly precipitation samples have been collected and analyzed for the composition of δ18O . The established local meteoric water line "D = 7.05δ18O - 2.17, based on the 50 monthly samples obtained, could be treated as isotope input functions across the region. The deviations of the slope and the intercept from the Global Meteoric Water Line indicated the specific regional meteorological conditions over Northwest China. The monthly δ18O values were characterized by a strong correlation with the surface air temperature and a weak correlation with precipitation amount. However, if only the % values during summer period have been taken into account, the amount effect visualized. Spatial distributions of δ18O have properly portrayed the atmospheric circulation background in each month over Northwest China. The quantitative simulation of δ18O, which involved a Rayleigh fractionation model and a kinetic fractional model, demonstrated that the kinetic fractionation was the dominating function of condensation of raindrops. Furthermore, the raindrops suffered re-evaporation during the falling process, and the precipitation vapor has been mixed with a quantity of local recycled water vapor. A multiple linear regression equation and a δ18O-T relation were gained by using meteorological parameters to evaluate physical controls on the long-term values. The established δ18O-T relation, which has been based on the present-day precipitation, was the first step of quantitatively reconstructing the paleo-climate.

Key words: Northwest China, δ18O, precipitation, water vapour source