台风水汽稳定同位素组成与天气过程的关系——以2015年13号台风“苏迪罗”为例

Stable Isotope Composition ofWater Vapor andWeather in Typhoon Process Relationships:A Case Study of Typhoon Soudelor(1513)

基于台风“苏迪罗”(1513)影响前后南京实时高频监测的水汽稳定同位素数据,并结合再分析资料、HYSPLIT后向轨迹模型分析了大气水汽δ^(18)O与天气过程之间的关系以及大气水汽过量氘所指示的水汽来源。结果表明,1)整个台风影响过程水汽δ^(18)O先保持基本不变后一直下降的趋势,而水汽过量氘则呈现完全相反的变化趋势。2)根据台风“苏迪罗”影响前后南京水汽δ^(18)O变化特征,将其划分为3个阶段:Ⅰ阶段水汽δ^(18)O较高与南京地区较为稳定的大气条件相对应,水汽过量氘值较低指示南京地区主要受海洋水汽影响;Ⅱ阶段台风环流及其残压和北方南下冷空气相互作用造成南京地区强降水,水汽凝结和降雨蒸发的共同作用导致水汽δ^(18)O不断贫化,较高的水汽过量氘表明南京地区主要受海洋和局地混合水汽的影响;Ⅲ阶段可能是中尺度下沉气流导致南京地区极端偏负的δ^(18)O和高水汽过量氘。

The stable hydrogen and oxygen isotopic composition of precipitation or water vapor not only shows the response to climate change on different time scales,but also has a strong relationship with typhoon extreme weather events.Typhoons usually bring destructive disasters,such as extreme rainstorms,strong winds,and storm surges,which have a significant social and economic impact worldwide.Therefore,the evolution of the typhoon weather process and the source of water vapor are worthy of attention.The stable isotope composition of water vapor can reflect more detailed weather process information than the stable isotope of precipitation,but available research on the stable isotope of water vapor in the atmosphere during a typhoon event is far less extensive and indepth than that of precipitation.Based on the real-time high-frequency monitoring of water vapor stable isotopes of Nanjing before and after the impact of typhoon Soudelor(1513)combined with reanalysis data,the HYSPLIT model focused on analyzing the relationship between water vaporδ^(18)O and weather processes and the water vapor indicated by excessive deuterium in the water vapor source.The results showed that the water vaporδ^(18)O remained primarily constant and then decreased,while the excess deuterium of water vapor showed a completely opposite trend to that of water vaporδ^(18)O.According to the change characteristics of water vaporδ^(18)O,it is divided into three stages:In the first stage,the highδ^(18)O level reflected the stable atmospheric conditions in Nanjing,and the low excess deuterium indicated that Nanjing was mainly influenced by marine water vapor.The low excess deuterium indicated that the water vapor source is consistent with the simulated water vapor source.In the second stage,the typhoon circulation and its residual pressure and the interaction of the cold air from the north to the south caused heavy precipitation in Nanjing.The combined effect of water vapor condensation and rainfall evaporation led to the continuous depletion of water vaporδ^(18)O,and the high water vapor excess deuterium indicated that the Nanjing area was mainly affected by the ocean and the influence of local mixed water vapor.The high excess deuterium indicated that the water vapor source was consistent with the model.In the third stage,the mesoscale downdraft may have led to the extremely negativeδ^(18)O and high water vapor excess deuterium in the study area,which is not consistent with the water vapor source simulated by the model,indicating that the water vapor excess deuterium was not only affected by the horizontal water vapor transport source,but also by the downdraft.The analysis of time series data of water vapor stable isotopes revealed the relationship between local and microphysical processes and the evolution of water vapor stable isotope composition.A full understanding of the stable isotopic composition of modern water vapor under typhoon extreme events can assist with the understanding and interpretation of isotopic data in geological archives.