3.1. Temperature, precipitation and its isotopes
A unimodal distribution was exhibited by temperature and precipitation amount in 2021, respectively (Figure 2a). Temperature peaked at the end of July (16.61℃) and decreased monotonically to the end of October (-6.62℃) during the observation. Precipitation activities were concentrated in the same time, accounting for 86.10% (465 mm) to the annual precipitation (540 mm). The δ18O and δ2H of precipitation showed large variations, the degree of enrichment and evaporative fractionation in May and October was more than in June to September, seasonal conditions are important factors that affect the isotope characteristics of precipitation, however, precipitation amount had little influence to δ18O and δ2H in precipitation (Figure 2b), temperature explained 49% to δ18O, whereas, 42% to δ2H (Figure 2c).