1.2. Estimating isotopic composition of vapor from Rain
Previous studies have suggested that monthly composite samples of rainfall can accurately predict the variability of isotopes in near ground-level vapor (Araguás‐Araguás, Froehlich, & Rozanski, 2000; Gammons et al., 2006). Estimating isotopic composition of ground level vapor from that of average monthly rainfall has a serious drawback because on a rainy-day, vapor interacts with falling raindrops and tends to attain isotopic equilibrium with rain. However, on cessation of rainfall, ground level vapor returns to its baseline isotopic composition (R. D. Deshpande, Maurya, Kumar, Sarkar, & Gupta, 2010). It has also been observed in certain cases that the signature of tropospheric vapor differs significantly from that of precipitation in tropical areas indicating significant role of evapotranspiration (J. Worden et al., 2007). The biggest limitation of estimating vapor composition from rain is that this method is not applicable on non-rainy days and hence create data gap.