移出型高原低涡对我国东部地区降水的影响

Influence of the Moving-Out Xizang Plateau Vortex on Precipitation in East China

摘要: 高原低涡是青藏高原夏季重要的天气系统，其中移出高原后仍能维持并影响下游地区的低涡，常引发我国东部大范围强降水。为揭示2000年代移出型高原低涡的活动规律及其与降水分布的关系，本文利用2000~2009年MICAPS历史天气图资料和NCEP再分析资料，对每年6~8月移出型高原低涡进行普查统计，并分析不同移动路径对应的降水特征。结果表明：2000~2009年共出现移出型高原低涡61次，年均6次。涡源集中于三个区域：西部(西藏狮泉河、改则和申扎之间)；中部有两个集中区(托托河以北的青、藏、新交界处及西藏那曲、班戈、安多附近)；东部(青藏高原东部的曲麻莱和德格附近)。移动路径以偏东路径为主(57.4%)，其次为东北移(27.9%)、东南移(11.5%)，极个别向北移(3.2%)。6月移出次数约占总数50%，7月与8月基本持平(各约25%)。结论认为：移出型高原低涡的移动路径与引导系统的变化密切相关，移动路径上对应明显的雨区；维持或发展的低涡在移动过程中会带来大范围降水，降水强度与低涡活动呈正相关。

Abstract: The Qinghai-Xizang Plateau vortex is an important weather system in summer over the Xizang Plateau. Those vortices that can move out of the plateau and maintain themselves often cause extensive heavy precipitation in eastern China. To reveal the activity characteristics of moving-out plateau vortices in the 2000s and their relationship with precipitation distribution, this study uses MICAPS historical weather charts and NCEP reanalysis data from 2000 to 2009 to conduct a census of moving-out plateau vortices from June to August, and analyzes the precipitation features corresponding to different movement paths. The results show that from 2000 to 2009, a total of 61 movingout plateau vortices occurred, with an average of 6 per year. Their source regions are concentrated in three areas: the western source (between Shiquanhe, Gaize, and Shenzha in Xizang); the central source (two concentrated areas, one near the junction of Qinghai, Xizang and Xinjiang north of Tuotuo River, the other near Naqu, Baingoin and Amdo); and the eastern source (near Qumalai and Dêgê on the eastern Qinghai-Xizang Plateau). The dominant movement path is eastward (57.4%), followed by northeastward (27.9%), southeastward (11.5%), and only rarely northward (3.2%). The frequency in June accounts for about 50% of the total, while July and August each account for about 25%. It is concluded that the movement paths of movingout plateau vortices are closely related to the steering flow, with corresponding precipitation belts along the paths. Vortices that maintain or intensify during movement can bring widespread precipitation, and the precipitation intensity is positively correlated with vortex activity.