Influence of below-cloud secondary evaporation on stable isotope composition in precipitation and its relationship with meteorological factors in Shiyang River Basin, Northwest China

In arid regions, the process of precipitation from the cloud base to the ground is often affected by the below-cloud secondary evaporation, which changes the ratios of hydrogen and oxygen stable isotopes in falling raindrops. Based on stable isotopes of 670 precipitation samples and meteorological records at 11 stations in the Shiyang River Basin, and combined with the improved Stewart model, this study discussed the impact of different meteorological factors on below-cloud secondary evaporation. The result showed that the Local Meteoric Water Line (LMWL) of the Shiyang River Basin is δD = 7.70δ 18 O + 8.90 ( r 2 = 0.98, p