Stable isotope compositions of precipitation over Central Asia.

Central Asia is one of the driest regions in the world with a unique water cycle and a complex moisture transport process. However, there is little information on the precipitation δ¹⁸O content in Central Asia. We compiled a precipitation δ¹⁸O database from 47 meteorological stations across Central Asia to reveal its spatial-temporal characteristics. We determined the relationship between precipitation δ¹⁸O and environmental variables and investigated the relationship between δ¹⁸O and large-scale atmospheric circulation. The Central Asia meteoric water line was established as d2H = 7.30 δ¹⁸O + 3.12 (R2 = 0.95, n = 727, p < 0.01), and precipitation δ¹⁸O ranged from +2‰ to -25.4‰ with a mean of -8.7‰. The precipitation δ¹⁸O over Central Asia was related to environmental variables. The δ¹⁸O had a significant positive correlation with temperature, and the δ¹⁸Otemperature gradient ranged from 0.28‰/°C to 0.68‰/°C. However, the dependence of δ¹⁸O on precipitation was unclear; a significant precipitation effect was only observed at the Zhangye and Teheran stations, showing δ¹⁸O-precipitation gradients of 0.20‰/mm and -0.08‰/mm, respectively. Latitude and altitude were always significantly correlated with annual δ¹⁸O, when considering geographical controls on δ¹⁸O, with δ¹⁸O/LAT and δ¹⁸O/ALT gradients of -0.42‰/° and -0.001‰/m, respectively. But both latitude and longitude were significantly correlated with δ¹⁸O in winter. The relationship between δ¹⁸O and large-scale atmospheric circulation suggested that the moisture in Central Asia is mainly transported by westerly circulation and is indirectly affected by the Indian monsoon. Meanwhile, the East Asian monsoon may affect the precipitation δ¹⁸O content in westerly and monsoon transition regions. These results improve our understanding of the precipitation δ¹⁸O and moisture transport in Central Asia, as well as the paleoclimatology and hydrology processes in Central Asia. [ABSTRACT FROM AUTHOR]