河南宝天曼大气降水稳定同位素特征及水汽来源

Stable Isotope Characteristics and Water Vapor Sources of Atmospheric Precipitation in Baotianman,Henan Province

【目的】探究中国暖温带−北亚热带过渡区河南宝天曼大气降水稳定同位素特征及水汽来源,为准确预测气候过渡区大气降水的时空分布格局提供科学依据。【方法】测定了宝天曼地区2021年5月至2023年4月(2个水文年)128次降水的稳定同位素(δD和δ^(18)O)组成,为了确定影响降水δD(δ^(18)O)组成的因素,采用Pearson相关性分析确定降水δD(δ^(18)O)与气象因子(降水量、空气温度、相对湿度等)的关系,并运用拉格朗日积分轨迹模型(HYSPLIT)模拟大气气团水汽来源。【结果】宝天曼地区大气降水线方程为:δD=7.86δ^(18)O+12.29(n=128,R^(2)=0.96,P<0.05),其斜率较全球大气降水线斜率偏低。大气降水δD(δ^(18)O)和过量氘呈现出明显的季节变化,整体上呈生长季期间偏低和非生长季期间偏高的特点。该地区降水来源也存在季节变化,非生长季水汽来源于印度西南季风气流、中纬度西风气流及局地的水汽蒸发,生长季水汽来源于中南半岛南海气流及中纬度西风气流。宝天曼地区大气降水δD(δ^(18)O)在年尺度上与降水量呈显著负相关,表现出降水量效应。此外,在年尺度上,过量氘与日照时间、空气温度、水汽压、太阳总辐射及光合有效辐射呈显著的负相关关系,而与大气压呈显著的正相关关系。【结论】水汽来源的季节和高度变化通过影响降水量间接影响大气降水δD(δ^(18)O)组成,局地环境因子直接影响大气降水δD(δ^(18)O)组成。研究补充了宝天曼地区大气降水δD(δ^(18)O)数据,同时为研究宝天曼森林生态系统水循环过程提供科学依据。

【Objective】It is critical to explore the stable isotope characteristics and water vapor sources of atmospheric precipitation in Baotianman,Henan Province,warm temperate-northern subtropical transition zone in China,which could provide scientific basis for predicting the temporal and spatial distribution pattern of precipitation in climatic transition zone.【Method】We determined theδD andδ^(18)O in 128 precipitation events from May 2021 to April 2023(2 hydrological years)in Baotianman area.To analyze the factors affecting theδD andδ18O in precipitation,we established the relationships ofδD(δ18O)and meteorological factors such as rainfall,air temperature and relative humidity by Pearson correlation analysis.We employed the Hybrid Single Particle Lagrangian Integrated Trajectory Model(HYSPLIT)to simulate the water vapor source of atmospheric air mass.【Result】The local meteoric water line in Baotianman wasδD=7.86δ^(18)O+12.29(n=128,R^(2)=0.96,P<0.05).Its slope was lower than that of the global meteoric water line.TheδD(δ^(18)O)and d-excess of precipitation in Baotianman area showed obvious seasonal variation,with a trend of being lower during the growing season and higher during the non-growing season.The source of precipitation in this area also exhibited seasonal changes.The water vapor in the non-growing season came from the southwest monsoon airflow in India,the mid-latitude westerly airflow and local water vapor evaporation,while the water vapor in the growing season stemmed from the South China Sea airflow in the Indochina Peninsula and the mid-latitude westerly airflow.δD(δ^(18)O)of precipitation in Baotianman area were significant negatively correlated with precipitation on the annual scale,indicating a precipitation effect.In addition,on the annual scale,d-excess had a significant negative correlation with sunshine time,air temperature,water vapor pressure,total solar radiation and photosynthetic active radiation,while it had a significant positive correlation with atmospheric pressure.【Conclusion】The seasonal and height changes of water vapor sources indirectly affect theδD(δ^(18)O)of precipitation by impacting rainfall,whereas local environmental factors directly affect theδD(δ^(18)O)of precipitation.This study supplemented the data ofδD(δ^(18)O)in precipitation in Baotianman area,and provided a scientific basis for exploring the water cycle process of Baotianman forest ecosystem.