Characteristics of δ 18O in precipitation over Eastern Monsoon China and the water vapor sources

Abstract

Monsoon circulation is an important carrier of water vapor transport, and it impacts the precipitation of the monsoonal regions through the constraints and controls of large-scale water vapor transport and distributions as well as the water vapor balance. An overall research on stable Hydrogen and Oxygen isotopes in precipitation over Eastern Monsoon China could benefit a comprehensive understanding of the monsoonal precipitation mechanism. Seventeen field stations of the Chinese Network of Isotopes in Precipitation (CHNIP) have been selected to collect monthly composite precipitation samples during the years 2005–2006. Components of δD and δ18O have been analyzed to achieve the spatiotemporal distributions. The established Local Meteoric Water Line δD=7.46δ18O+0.90 based on the 274 obtained monthly samples could be treated as isotope input functions across the region, due to basically reflecting the specific regional meteorological conditions over Eastern Monsoon China. The δ-value depleted from coastal to inner area. In Southern China and Northeastern China there were typical periodic patterns of δ18O. Different dominant affecting metrological factors have been raised with different regions. From south to north, the temperature effect of δ18O enhanced, while the amount effect changed from existing at an all-year-scale in Southern China to being only remarkable during the main rainy seasons in North China and Northeastern China. Main geographical controls varied from altitude in Southern China and North China to latitude in Northeastern China. Furthermore, δ18O had an implication of advance and retreat of the monsoon as well as rainfall belt transfer. δ18O was also a tracer for the movement path of typhoon and tropical storms.