2013年南疆西部暴雨天气的水汽特征

Water Vapor Characteristics of Rainstorm Weather Processes over Western South Xingjiang in 2013

应用南疆西部(35°~42°N,73°~80°E)15个气象站及200个区域自动气象站2013年逐日降水量资料和NCEP/NCAR每日4次1°×1°再分析资料,分析2013年南疆西部4次典型暴雨天气过程的水汽源地、水汽输送及水汽收支特征。结果表明,2013年4场暴雨天气水汽主源地主要分布在阿拉伯海和孟加拉湾,其次是波斯湾,低层东风急流(LLEJ)在南疆西部暴雨过程中作用显著。过程Ⅰ水汽输送路径主要为偏东和西南气流,在南疆西部沿山及偏东平原强烈辐合引发暴雨,偏东路径水汽输送明显大于西南路径,水汽输送的大值区域持续时间为24h。过程Ⅱ水汽输送有西方、西南和偏东路径,3支水汽输送在南疆西部东—西、南—北产生剧烈的辐合造成大范围、强度强的暴雨天气,东边界水汽输入量接近南边界,水汽输送的大值区域持续时间为60h。过程Ⅲ水汽输送为西方、偏南和偏东路径,LLEJ引导的水汽在西风、东风气流的交汇下沿山堆积产生强的辐合,造成暴雨天气。水汽输送的大值区域持续时间为24h。过程水汽输送主要有西方、偏南和偏东路径,西方路径的输送量远远大于偏东和偏南水汽,水汽输送出现2次高低空大值区域叠置现象,暴雨过程中大值区域持续时间48h。

Using the NCEP/NCAR reanalysis data （1°×1°） and the daily precipitation data of 15 weather stations and 200 regional automatic stations over the western South Xinjiang （35° to 42°N, 73° to 80°E） in 2013, the source region, transportation, and budget features of the water vapor associated with four typical rainstorm processes over the region are analyzed. The results show that in these processes, where a strong low-level easterly jet （LLEJ） played a significant role, the vapor sources mainly were the Arabian Sea and the Bay of Bengal, followed by the Persian Gulf. In Process 1, the vapor was mainly transported via the easterly and southwesterly. The strong convergence over the mountains in the west and the plain in the east of South Xinjiang triggered the rainstorm. The vapor transportation with high value lasted for 24 hours, was lager in the easterly path than the southwesterly one. In Process 2, there were three paths of vapor transportation： westerly, southwesterly, and easterly, which all generated severe convergence over the western South Xinjiang and induced the extensive and strong rainstorm. The vapor input of the easterly boundary was close to that of the southerly one. The vapor transportation of high value lasted for 60 hours. In Process 3, the vapor transportation was along the westerly, southerly and easterly path. The vapor led by LLEJ, under the intersection of the westerly and easterly, heaped up along the mountains, producing the strong convergence and the rainstorm. The vapor transportation of high value lasted for 24 hours. In Process 4, the vapor transportation was mainly along the westerly, southerly, and easterly paths. The vapor input of the westerly was much larger than that of the easterly and southerly. There appeared for 2 times that the high-value vapor transportation areas of lower and upper levels were superposed, during which the area with high-value vapor lasted for 48 hours.