基于“黄河源区玛曲-若尔盖土壤温湿监测网络”自2008年观测以来至2017年的观测资料， 通过分析多层土壤湿度异常百分比指数SMAPI（Soil Moisture Anomaly Percentage Index）， 捕捉10年来该地区的干湿演变过程， 并利用再分析数据资料NECP FNL （National Centers for Environmental Prediction Final）驱动拉格朗日后向轨迹模式， 模拟不同过程的水汽输送粒子（气块）的后向轨迹， 从而诊断到达该区域的水汽输送路径以及可能的水汽源区。结果表明， 水汽路径可以分为3条： （1）南支输送： 来自印度洋、 阿拉伯海的水汽， 通过印度半岛、 孟加拉湾， 从青藏高原西侧和南侧进入； （2）东支输送： 来自太平洋、 南海等地的水汽从华东/华南地区， 途径长江流域， 从青藏高原东侧或者南侧进入； （3）北支输送： 来自大西洋、 非洲大陆北部和欧洲大陆的水汽， 穿过中纬度亚欧大陆， 从青藏高原西部或者北部进入。在干旱时期以北支为主， 湿润时期以南支、 东支为主。水汽源地在不同时期的表现也各不相同， 其中青藏高原上的水汽源地在湿润时期主要分布在昆仑山脉附近， 演变时期则南北零星分布， 而干旱时期更加偏北集中在天山附近， 伊朗高原、 帕米尔高原及孟加拉湾的水汽源地强度从湿润到干旱时期逐渐增强， 四川盆地-秦岭、 华南的水汽源地强度先增强后减弱， 而祁连山-黄土高原先减弱后增强， 印度半岛、 长江中下游及华东附近的水汽源地强度则是从湿润时期到干旱时期一直减弱。

By analyzing Soil Moisture Anomaly Percentage Index （SMAPI） at different soil layers， dry-wet evolution of the source region of the Yellow River （SRYR） during 2008 -2017 are investigated using observations from the Maqu-Ruoergai soil temperature and moisture monitoring network.To diagnose the water vapor transportation path and potential water vapor sources in different processes， the Lagrange Flexible Particle Dispersion Model （FLEXPART）， which is driven by reanalysis data （National Centers for Environmental Prediction Final， NECP FNL）， are used to simulate the backward trajectories of target particles.The results show that the water vapor transportation path can be divided into three categories： （1） South Branch transportation.The water vapor origins from the Indian Ocean and the Arabian Sea， and finally arrives at the SRYR by way of the Indian Peninsula and Bay of Bengal； （2） East Branch transportation.The water vapor is from the Pacific Ocean and the South China Sea， then passes through the Yangtze River Basin， and finally arrives at the SRYR from eastern and southern flank of the Tibetan Plateau； （3） North Branch transportation.The water vapor is from the Atlantic Ocean， the northern African continent， and the European continent， then arrives at the SRYR from the western or northern side of the Tibetan Plateau by way of the mid-latitude Eurasian continent.Moreover， the North Branch is dominant in dry period， whereas the South and East branches are prominent in wet period.The water vapor sources also show discrepancies for dry and wet periods.The water vapor sources of the Tibetan Plateau are mainly distributed around the Kunlun Mountains during wet period， and are scattered distributed from north to south during transitional period， and are located around the Tianshan during dry period.The intensity of the water vapor sources of the Iranian Plateau， Pamir Plateau， and the Bay of Bengal gradually strengthen from wet to dry period， the intensity of the water vapor sources of the Sichuan Basin-Qinling Mountains and south China enhanced first and then weakened， while the source of Qilian Mountain-Loess Plateau weakened after enhanced.The intensity of water vapor sources over the middle and lower reaches of the Yangtze River and around East China has been weakening from the wet period to the dry period.