Arid Zone Research ›› 2022, Vol. 39 ›› Issue (1): 21-29.doi: 10.13866/j.azr.2022.01.03

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Simulation of stable hydrogen and oxygen isotopes in atmospheric water vapor based on an evaporation pan experiment

LEI Shijun1,2(),WANG Shengjie1,2(),ZHU Xiaofan3,ZHANG Mingjun1,2   

  1. 1. College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, Gansu, China
    2. Key Laboratory of Resource Environment and Sustainable Development of Oasis, Gansu Province, Lanzhou 730070, Gansu, China
    3. Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China
  • Received:2021-04-19 Revised:2021-07-26 Online:2022-01-15 Published:2022-01-24
  • Contact: Shengjie WANG E-mail:geolei@163.com;geowang@126.com

Abstract:

The stable hydrogen and oxygen isotopes in atmospheric water vapor reflect the key processes of water transport, mixing, and phase change in the atmosphere. The stable isotopic compositions of hydrogen and oxygen in atmospheric water vapor can be simulated using an evaporation pan experiment, but a measurement-based assessment of model reliability is necessary. In this study, an evaporation pan experiment was conducted in Lanzhou, Gansu, from September to November 2019. The daily atmospheric water vapor isotopes were simulated using the Craig-Gordon linear resistance model and the water isotopic mass balance method in a natural evaporative state. Online observations of atmospheric water vapor isotopes were performed using a water vapor isotope analyzer and then the pan-based simulations were verified. The simulated δ 18O in atmospheric water vapor and the directly measured δ 18O were in good agreement with a root mean square error of 4.5‰, a mean absolute error of 3.2‰, and a mean bias error of 0.03‰.The residual of simulated δ18O values were correlated with relative humidity (R2=0.43), remaining ratio (R2=0.39), and the isotopic values of the remaining water bodies (R2=0.39). The model was highly sensitive to relative humidity: lower relative humidity conditionstypically corresponded to a higher error. Under the conditions of low remaining ratio and isotopically enriched remaining water at the end of the evaporation experiment, the simulation residual was much larger than that at the beginning of the experiment.

Key words: stable hydrogen and oxygen isotopes, evaporation pan, simulation, atmospheric water vapor