3.1 The variations of precipitation isotopic compositions and meteorological parameters
In this study, the values of δD varied from −105.36‰ to 29.51‰, and the values of δ18O ranged from −11.94‰ to 3.61‰ (Fig. 2). Obvious seasonal variations were observed from June 2018 to August 2019, that changed with variations of meteorological parameters. There was an obvious decreasing trend in the time between June 2018 and August 2018, and then an increase until December 2018. From December 2018 to May 2019, δD and δ18O maintained a high value, which then decreased until August 2019.
[Insert Figure 2]
The deuterium excess (D-excess, D-excess = δD − 8δ18O) is generally controlled by the evaporative conditions at the moisture source region which include sea surface temperature, humidity, and wind speed, etc. (Frohlich et al., 2002; Quezadas et al., 2021). D-excesses in this study fluctuated from −31.32‰ to 20.52‰ with a mean value of 2.26‰. The D-excess values are mostly lower than 10‰ in this study, and clearly higher in summer samples than that in winter samples.
In addition, both the isotopes (δ18O and δD) and D-excess of typhoon-related precipitation are clearly lower than that of normal precipitation in summer (Table 1, Fig. 2).