Continuous observation of Stable Isotopes of Water Vapor in Atmosphere Using High-Resolution FTIR

Abstract. Observations of stable isotopes of water vapor provide important information for water cycle. The volume mixing ratios (VMR) of H₂O (X_H2O) and HDO (X_HDO) have been retrieved based on a high-resolution ground-based Fourier transform infrared spectroscopy (FTIR) at Hefei site, and the isotopic composition δD was calculated. Time series of X_H2O were compared with the Greenhouse gases Observing Satellite (GOSAT) data, showing a good agreement. The daily averaged δD ranges from −17.02 ‰ to −282.3 ‰ between September 2015 and September 2016. Also, the relationships of meteorological parameters with stable isotopologue were analyzed. δD values showed an obvious positive correlation with temperature and ln(X_H2O) and a weak correlation with relative humidity. Further, 51.35 % of airmass at Hefei site comes from the southeast of China, and the main potential sources of δD are in the east of China over the observation period based on the back trajectories model. Furthermore, the δD values of evapotranspiration were calculated based on Keeling plot. Observations of the stable isotopes of water vapor by high-resolution ground-based FTIR provide information on study of the variation of the atmospheric water vapor at Hefei site.