西南地区夏季大气水汽含量及其与南亚高压关系

利用欧洲中期天气预报中心 (ECMWF) 提供的ERA-interim高分辨率资料，借助经验正交函数 (EOF) 分解、距平合成和相关分析等方法，讨论1979—2014年我国西南地区夏季大气水汽含量的时空变化特征及其与南亚高压的关系。研究结果表明:我国西南地区夏季大气水汽含量空间分布形态主要有全区一致型、南北振荡型和东西振荡型。全区一致型 (EOF1) 能够反映西南地区夏季水汽含量的主要特征，西南地区夏季大气水汽含量具有明显的年际变化特征；西南地区夏季大气水汽含量与南亚高压强度指数、面积指数及东伸指数均存在非常显著的正相关关系；南亚高压的异常偏强，有利于南海地区水汽向西南地区输送，且在西南地区气流由低层向高层的上升运动显著增强，引起西南地区大气水汽含量的异常偏多。

Characteristics of Water Vapor Content in Southwest China and Its Association with the South Asia High in Summer

Based on ERA-interim high resolution data by ECMWF from 1979 to 2014, in terms of EOF decomposition, wavelet transform, anomaly composite and correlation analysis, spatial and temporal variations of atmospheric water vapor content in Southwest China and its relationship with the South Asia High in summer are discussed. Results indicate that the spatial distribution morphology of summer atmospheric water vapor content in Southwest basically has the same anomaly in whole type, north-south oscillation type and east-west oscillation type, and the explained variance of EOF1 is much higher than those of EOF2 and EOF3, which means the same anomaly in whole type (EOF1) can reflect the main distribution characteristic of water vapor content in Southwest China in summer. The summer atmospheric water vapor content in Southwest China shows obvious inter-annual variation characteristics, and there is obviously corresponding relationship between summer atmospheric water vapor content in Southwest China and the South Asia High. More (less) water vapor content is accompanied with stronger (weaker) South Asia High. Furthermore, there are significant positive correlations between the water vapor content in Southwest China and the South Asia High intensity index, the area index and the eastward index, which reach 0.64, 0.62 and 0.59, respectively. In addition, when the South Asia High strengthens, the subtropical high over the West Pacific extends to west, and the southwest airflow of the lower troposphere is enhanced, which is favorable for the water vapor transport to the south of China from the ocean. Meanwhile, the South Asia High enhances the upward motion in Southwest China, causing more water vapor content. On one hand, the westward extension and the strengthening of subtropical high guides the Western Pacific water vapor transport to the southwest of China; on the other hand, due to blocking effects of the subtropical high, the water vapor which transported from the South China Sea leads to increased atmospheric water vapor content in Southwest China. When the South Asia high is weakened, the situation is the opposite.