Temporal variations of precipitation driven by local meteorological parameters in southwest China: Insights from 9 years of continuous hydro-meteorological and isotope observations

Study region: Northwest of Guangxi Province, southwest China. Study focus: Knowing the role of isotopes in precipitation can improve understanding of climate change and eco-hydrological processes in complex critical-zone systems. However, knowledge of the influence of local meteorological factors on variations of precipitation isotopes remains limited as high-resolution rainwater sampling is lacking. New hydrological insights for the region: The temporal characteristics (intra-annual, seasonal, and monthly scales) of precipitation were analyzed using daily precipitation isotopes data from 2011 to 2020 and event-resolving data from 2019 to 2020 at Huanjiang in southwest China. The boosted regression tree model was used to explore the relationship between local meteorological factors and δ18O values. On an intra-annual scale, δ18O, δD, and d-excess values exhibited significant sinusoidal fluctuation, being lower and higher during the wet and dry seasons respectively. Temperature is the most sensitive meteorological factor to monsoon climate response. On the seasonal scale, ET0 explains 37.5% of isotopic variations in the dry season, thus indicating that the influence of evaporation on the rainwater isotopes variation should be considered. The “amount effect” of rainwater isotopes was clearly shown on the monthly scale. However, precipitation isotopes did not follow the “amount effect” on an inter-event scale, which can be explained by large-scale convection activity. These findings can improve interpretations of isotopic variations in precipitation in humid subtropical climate zones.