拉萨河源廓琼岗日冰川流域降水δ^(18)O变化特征及影响因素  

Variation characteristics and controlling factors of precipitation δ~(18)O in Kuoqionggangri Glacier region,source of the Lhasa River

作　　者：杨佳馨 德吉[1,3] 姚檀栋 曲冬梅[1] 于正良 旦增白姆[5] YANG Jiaxin;Deji;YAO Tandong;QU Dongmei;YU Zhengliang;Danzeng Baimu(State Key Laboratory of Tibetan Plateau Earth System,Environment and Resources(TPESER),Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101,China;University of Chinese Academy of Sciences,Beijing 100049,China;Lhasa Earth System Multi-Dimension Observatory Network(LEMON),Beijing 100101,China;College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,China;Animal Husbandry General Station of Tibet Autonomous Region,Lhasa 850000,China)

机构地区：[1]中国科学院青藏高原研究所,青藏高原地球系统与资源环境全国重点实验室,北京100101 [2]中国科学院大学,北京100049 [3]拉萨河流域生态环境保护修复治理地球系统科考平台,北京100101 [4]兰州大学资源环境学院,甘肃兰州730000 [5]西藏自治区畜牧总站,西藏拉萨850000

出　　处：《冰川冻土》2024年第6期1715-1727,共13页Journal of Glaciology and Geocryology

基　　金：第二次青藏高原综合科学考察研究项目(2019QZKK0208);国家自然科学基金项目(42101133,42203060)资助。

摘　　要：降水氢氧稳定同位素(δ^(18)O和δ^(2)H)作为水循环过程的有效示踪剂,可以揭示水汽来源和水汽传输路径。为了认识季风和西风水汽来源对拉萨河源廓琼岗日冰川流域降水δ^(18)O的影响,利用2020年7月—2023年7月期间在廓琼岗日3个采样点收集的347个事件降水样品,研究了该区降水δ^(18)O的变化特征、大气降水线及其与气象要素和对流活动的关系。结果发现,研究区内冰川末端(海拔5544.5 m)、流域源头(海拔5374.0 m)和流域出口(海拔4941.3 m)3个采样点2020年7月—2023年7月期间的温湿度、降水量差异较小;并且在2020年7—8月期间,3个采样点降水δ^(18)O和降水线均相近,反映了廓琼岗日冰川流域内部气候差异较小。分析流域出口处2020年7月—2023年7月期间降水δ^(18)O显示,日尺度降水δ^(18)O以6月中旬为界,前一阶段较高,后一阶段较低;月尺度降水δ^(18)O极高值在6月,极低值在9月。流域内季风期降水线的斜率和截距(8.12、11.78)明显小于非季风期(8.79、23.18),反映了季风期降水的水汽来源地具有较高的相对湿度;全年范围(8.27、15.10)和季风期降水线的斜率和截距更相近,可能与该流域内季风期降水占全年降水比例较大有关。廓琼岗日冰川流域季风期降水δ^(18)O在月尺度上呈显著的温度效应,全年范围降水δ^(18)O在日尺度上呈显著的降水量效应。降水事件前1~6天的对流活动对降水δ^(18)O具有贫化作用,并且其影响在季风期较明显。后向轨迹追踪表明,印度季风携带的水汽为该区域带来了几乎全年的降水,季风会使该区域降水δ^(18)O逐渐贫化。以上研究内容初步揭示了青藏高原南部高寒山区降水δ^(18)O的变化特征及其影响因素,可为高寒地区水循环研究提供基础资料。In the water cycle,water bodies show different characteristics of stable hydrogen and oxygen isotopes(δ^(18)O and δ~2H) in different processes of evaporation,transport,convection,and condensation due to the influences of isotope fractionation.Therefore,δ^(18)O and δ~2H is widely used in the study of paleoclimate and modern hydrological processes.Previous studies mainly focused on the variations of precipitation stable isotopes in the low-altitude regions in the Lhasa River basin,a critical area for the studies of the progressing and evolution of monsoon and westerly wind systems.In contrast,studies on δ^(18)O and δ~2H data obtained from the alpine regions are largely lacking.In this study,we analyzed 347 event scale precipitation samples collected at three sampling sites in the Kuoqionggangri Glacier region from July 2020 to July 2023.The spatial and temporal variations of precipitation δ^(18)O,the local meteoric water lines,the relationship between precipitation δ^(18)O and meteorological factors,and the relationship between precipitation δ^(18)O and convective activity are investigated to understand the influences of the Indian monsoon and westerly wind on the precipitation δ^(18)O and δ~2H in the Kuoqionggangri Glacier region at the source of the Lhasa River of the southern Qinghai-Xizang Plateau.Besides,the backward trajectory of water vapor was further demonstrated through correlation analysis and cluster analysis,so as to reveal sources of water vapor.The results showed that there was little difference in temperature,relative humidity,and precipitation among the three fixed points located in different altitudes in this study area from July 2020 to July2023 (the glacier terminus (5 544.5 m a.s.l.),the basin source (5 374.0 m a.s.l.) and the basin export(4 941.3 m a.s.l.)).In addition,the precipitation δ^(18)O and local meteoric water lines were similar among these three sampling sites from July 2020 to August 2020.This suggested that the climate conditions remained relatively identical within the

关 键 词：廓琼岗日 降水δ^(18)O 局地大气降水线 气候因素 对流活动 水汽来源 

分 类 号：P342[天文地球—水文科学] P343.6[天文地球—地球物理学]