Influences of variability of stable isotopes and composition of moisture sources on precipitation at multiple timescales in the Alpine regions of Central Asia

The accurate representation of variability of isotopic composition of modern precipitation based on long-term continuous monitoring is vital for interpreting hydrological and climatic processes. Based on measurements of delta 2H and delta 18O of 353 precipitation samples from five stations in the Alpine Mountains of Central Asia (ACA) during 2013-2015, the spatiotemporal variability of isotopic composition of precipitation and its controlling factors under multiple timescales were explored. Results showed that (1) the stable isotopes in precipitation at multiple timescales displayed an obviously inconsistent trend, especially in winter. (2) delta 18O composition of precipitation (delta 18Op) under multiple timescales had a significant correlation with the variability of air temperature, except for in the case of the synoptic scale, while the correlation was weak between precipitation amount and variability in altitude. (3) The westerly wind had a stronger influence on the ACA, the southwest monsoon had an important influence on the transport of water vapor in the Kunlun Mountains region, and Arctic water vapor had a higher contribution to the region of the Tianshan Mountains. (5) The contribution rate of recycled vapor to precipitation ranged from 15.44 to 24.11 %, and the composition of moisture source of precipitation in arid inland areas of Northwestern China exhibited spatial heterogeneity. The results of this study improve our understanding of the regional water cycle and will enable the optimization of the allocation of regional water resources.

Automated summary

Based on measurements of stable isotopes of 353 precipitation samples in the Alpine Mountains of Central Asia from 2013 to 2015, this study explores the spatiotemporal variability of precipitation isotopes and their controlling factors. Results show inconsistent trends of precipitation isotopes at different timescales, significant correlation between delta 18O and air temperature, and weaker correlation between precipitation amount and altitude variability. The study also identifies the influence of westerly wind, southwest monsoon, and Arctic water vapor on the region, as well as the contribution of recycled vapor and spatial heterogeneity in moisture source.