Comparisons of Precipitation Isotopic Effects on Daily, Monthly and Annual Time Scales—A Case Study in the Subtropical Monsoon Region of Eastern China

Abstract

The study on precipitation isotope variation can potentially improve the understanding of weather processes, regional water cycle and paleoclimate reconstruction in the subtropical monsoon region. Based on the measured stable isotope composition in precipitation (δ18Op) and daily precipitation from January 2010 to December 2021 in Changsha of the subtropical monsoon region of eastern China, the δ18Op variations, amount effect and local meteoric water line (LMWL) were analyzed and compared on daily, monthly and annual time scales, as well as under different precipitation intensities. The results showed that, on the daily time scale, δ18Op was significantly and negatively correlated with precipitation in the study area. Influenced by subcloud evaporation, small precipitation events (≤5 mm/d) could change the rainout level of precipitation isotopes. There were significant differences in the slope and intercept of the LMWL on different time scales, in different seasons and under different precipitation intensities. On the daily and monthly time scales, the slope and intercept of the LMWL in the cold half of the year were significantly smaller and larger than those in the warm half of the year, respectively, and the slope and intercept of the LMWL increased significantly with precipitation intensity, and then remained largely stable. On the annual time scale, the slope and intercept of the LMWL in the cold half of the year were smaller than those in the warm half of the year. The possible reasons for the differences in the LMWL on different time scales are the combined effects of seasonal differences in precipitation intensity and water vapor sources.

Identifying river water sources using end‐member mixing analysis in a subtropical monsoon basin China

“…The average TDS contents of precipitation were relatively large in the dry or rainless months (January, February, July and December) during the observation period, but low in the spring rainy months during March to June in 2020 and 2021, showing the opposite pattern of seasonal variation to the precipitation amount (Figure 2). The standard deviations of the most solutes in river water and creek water were less than the mean values, while the standard deviations of all the precipitation solutes were larger than the mean values (Table 1), this indicated the large variations of the solute contents in precipitation, which may be related to the complex seasonality of the vapour sources of precipitation (Xiao et al, 2023). Moreover, the TDS values of the river water and creek water decreased substantially with the heavy precipitation inputs in late March, mid‐August, and early November, in 2020 and 2021 (Figure 2a, c).…”

Seasonal variation and influence factors of river water isotopes in the East Asian monsoon region: A case study in Xiangjiang River basin spanning 13 hydrological years

“…3b). The seasonal variations in the precipitation isotopes primarily result from different vapor sources, upstream effects, circulation patterns, and local meteorological factors in different seasons (Zhou et al, 2019;Xiao et al, 2023). The δ 2 H values of river water (δ 2 H R ) ranged from −63.7‰ to −21.7‰, with a standard deviation of 6.1‰ (Figs.…”