干旱区生态环境知识资源中心

Stable isotopes and deuterium excess in precipitation over China show distinctive differences during the summer and winter seasons. Contours of delta O-18 and delta D values exhibit the switched influence of different air masses in different seasons. In winter, higher deuterium excess values are found in the whole country, while in summer, only in regions south of 32 degrees N. Lower deuterium excess is found in regions north of 32 degrees N, probably due to stronger subcloud evaporation under arid to semi-arid conditions. Hydroclimatic sensitivity of isotopic signals in precipitation also varies considerably in different seasons. In winter, strong positive relationship exists between delta O-18 and air temperature, and this effect increases with increasing latitude for individual monitoring stations. In summer, a negative linear correlation can be found between delta O-18 and the amount of precipitation, and this effect plays an important role in regions north of 32 degrees N. There is a south-north divide (near approximately 32 degrees N) for the spatial variability of d-excess, Delta delta O-18, and the dominant factors controlling stable isotopes in precipitation.