青藏高原雨季降水的水汽条件研究

利用1961—2017年青藏高原109站降水量资料、NCEP全球逐月再分析资料，讨论了雨季期间高原的水汽输送特征。结果表明：高原雨季降水呈显著的年际变化特征，高原雨季降水主模态为南北反向型和全区一致型。气候态高原雨季的水汽输送路径为来自阿拉伯海的偏西风水汽输送，在孟加拉湾附近分为三支水汽输送气流：一支向北输送，自高原南缘输入；一支在南海附近转为偏南风水汽输送，自东南侧输入高原；一支受高原大地形的阻挡作用，转为偏西风水汽输送。在全区一致型降水偏多年，高原主体呈现北部弱辐合、南部辐散的分布形态；在全区一致型降水偏少年，来自阿拉伯海偏南水汽输送在25° N附近转为偏东水汽输送，在高原南缘形成较强的水汽辐合中心。雨季期间高原各边界的水汽收支情况表现为西、南、东边界以水汽输入为主，北边界为水汽输出，南边界水汽输入量最大，西边界次之。

Study on water vapor conditions of precipitation on the Tibetan Plateau during rainy season

Based on the precipitation data on the Tibetan Plateau and the monthly reanalysis data of NCEP during 1961—2017， the water vapor transport characteristics of the Tibetan Plateau during rainy season was discussed. The results are as follows： the average precipitation of the Tibetan Plateau during the rainy season （May to September） had a significant inter-annual change； there is dramatically difference between the southern and northern Tibetan Plateau in the first EOF mode， and the second EOF mode had the same anormaly in whole area. Climate moisture transport path on the Tibetan Plateau during rainy season is westerly wind from the Arabian Sea is divided into three steam delivery streams near the Bay of Bengal： one part goes north， some of them shifted to southerly winds near the South China Sea， some of them transferred to the westerly wind were blocked by the plateau topography. In the strong years of precipitation during rainy season， the main body of the plateau is characterized by northern convergence and southern divergence. In the weak years， the southerly water vapor flow from the Arabian Sea changes to an easterly water current near 25° N， a strong water vapor convergence center is formed at the southern edge of the plateau. During the rainy season， the water vapor budget at each boundary of the plateau is as follows： the west， south and east boundaries are dominated by water vapor input， only the north boundary is the water vapor output， and the south boundary is the largest water vapor input， followed by the west boundary.