中国东部季风区降水δ^18O与ENSO事件的关系

The Relationship betweenδ^18O in Precipitation in Eastern China and the ENSO

【目的】ENSO背景下的水汽源区变化、大尺度对流过程与季风区降水稳定同位素特征关系密切,研究水汽源区变化/ENSO事件与降水同位素特征的响应机制,有助于进一步明确东部季风区的水循环模式。【方法】基于我国东部季风区60个站点的降水同位素δ^18O及气象数据,运用向外长波辐射(OLR)技术研究ENSO事件与稳定同位素之间的响应机制。【结果】δ^18O值在空间上由东南向西北逐渐贫化,受地形影响显著,季节变化冬高夏低,ENSO事件对同位素的分馏状况具有较为规律性的影响;热带辐合带(ITCZ)的变化与季风区稳定同位素特征有着较强的对应关系,局地气候对同位素特征影响深刻。【结论】OLR场反演的水汽源区的位置、对流活动强度及气团运移过程对我国东部季风区稳定同位素特征有显著的影响。

【Background】Stable isotopes in precipitation are influenced by atmospheric moisture dynamics,precipitation pattern,temperature,humidity and altitude.The El Niño-Southern Oscillation(ENSO)is a Global Coupled Ocean-Atmosphere event that plays an important role in inter-annual climate change.The variation in atmospheric moisture and ENSO has a prominent impact on hydrological cycle and characteristics of isotopes in precipitation in monsoon season in east Asia.【Objective】This paper aims to analyze the response of stable isotopes in precipitation in east Asia to variation in atmospheric moisture and the ENSO in order to improve our understanding of water cycle in this region.【Method】We divided the region to three sub-regions:northeast,north and south.Based on the stable isotopes in precipitation and meteorological data measured from 60 weather stations across the region,a nonlinear regression model was derived to link latitude andδ^18O in the precipitation using the BW model to calculate spatial distribution of the stable oxygen isotopes.We also analyzed the temporal change inδ^18O and the meteorological data at each station.The relationship between the ENSO and the stable isotopes was analyzed using the OLR method.【Result】The concentration ofδ^18O decreased gradually from the southeast to the northwest and was affected by terrain at significant level;it was higher in winter and lower in summer.In general,the ENSO had a significant impact on temperature,and thus,in La Nina year,theδ^18O was related to the temperature strongly in the northeast and south while weakly in the north.The OLR value of the moisture showed that we can rank its impact in the order of El Nino year>normal year>La Nina year,consistent with the change inδ^18O.The change in ITCZ was strongly related to the stable isotope in the precipitation,but the impact varied with local climate and their correlation was not significant in the northeast.【Conclusion】Atmospheric moisture and air convection have a better correlation with the stable isotope in precipitation in east China.The results presented in this paper could improve our understanding of the impact of ENSO on stable isotopes which have a wide application.