雅鲁藏布江大峡谷区域作为高原的主要水汽输送入口， 自1979年至今水汽通量辐合及降水量呈持续减少趋势， 这对高原水储量具有重要影响。为了探究该区域水汽输送减少的原因， 本文利用ERA5逐小时再分析资料驱动LAGRANTO模型， 选取典型干旱年份和湿润年份的夏季（6 -8月）， 后向追踪该区域的水汽输送轨迹， 对沿轨迹输送的水汽通量变化进行对比分析。研究发现， 源自洋面的水汽主要来自高原南部的孟加拉湾， 高原西南侧的阿拉伯海， 赤道以南的印度洋以及南中国海四个区域， 水汽输送主要受南亚和印度夏季风控制， 并受索马里跨赤道急流影响。通过对比分析干、 湿年份的水汽输送轨迹的特征， 发现干湿年轨迹路径除南海源地外基本不变， 轨迹上水汽通量随轨迹高度抬升而减少， 且湿润年的损耗始终低于干旱年， 其中孟加拉湾源地的轨迹得到洋面的水汽补充， 在湿润年水汽通量有较强的增长。干湿年份的蒸发、 降水、 环流场形势的对比也佐证了这一发现。最终湿润年到达雅鲁藏布江峡谷边界的水汽通量大于干旱年， 尤其是经由雅鲁藏布江峡谷区域南边界进入的水汽通量显著增大， 这表明， 除源地水汽贡献和大尺度季风环流影响外， 水汽输送途中的降水损耗相关过程对雅鲁藏布江峡谷区域水汽收支具有决定性作用。

The Yarlung Tsangpo River Grand Canyon region serves as a main water vapor entrance for the Tibetan plateau.However， the region has been experiencing a persistent decline in both water vapor convergence and precipitation since 1979， which has an important impact on the water storage over the Tibetan Plateau.In order to investigate the reasons behind this reduction in water vapor transport in the area， ERA5 hourly reanalysis data were utilized to drive the LAGRANTO model to derive the backwards water vapor transport trajectories in the region during the boreal summer （June to August） of typical dry and wet years， facilitating a comparative analysis of alterations in moisture flux along these trajectories.It was found that the water vapor sources primarily originating from four oceanic regions： the Bay of Bengal in the southern plateau， the Arabian Sea on the southwest side of the plateau， the Indian Ocean around south of the equator， and the South China Sea.The water vapor transportation in these regions is predominantly governed by the South Asian and Indian summer monsoons and influenced by the Somalia cross-equatorial jet.By comparing the characteristics of water vapor transport trajectories in dry and wet years， it is evident that trajectory patterns remain largely unchanged， with the exception of the South China Sea source.Furthermore， moisture flux along these trajectories diminishes as elevation increases， and the moisture loss during wet years consistently proves to be lower than that during dry years.Additionally， the trajectories originating from the Bay of Bengal source are supplemented by water vapor from the ocean surface， resulting in significant increased water vapor flux in wet years.This finding is supported by comparing the evaporation， precipitation， and circulation fields between dry and wet years.Ultimately， during wet years， the moisture flux reaching the boundaries of the Yarlung Tsangpo Grand Canyon region surpasses that of dry years， notably marked by a particularly significant increase in moisture entering through the southern boundary.This highlights that the depletion processes during water vapor transport， in addition to contributions from moisture sources and the influence of large-scale monsoonal circulation， play a critical role in determining the moisture equilibrium within the Yarlung Tsangpo Grand Canyon region.