摘要
文章分析了陕西省2003年秋季连阴雨降水的特征和形成秋季连阴雨天气的天气学、热力学特点。结果表明:2003年陕西秋季连阴雨降水的主要特征是降水的落区和时间相对集中,降水强度大,日数多且持续时间长,是1954年以来陕西又一次极端连阴雨事件。在大气环流由夏季型向冬季型转变过程中,对流层高层西风急流南压至40°N时,青藏高原东北侧包括陕西在内的西北地区东部,位于急流南侧的高空辐散区,该地区对流层低层却保持着高温高湿的热力特征,对流上升运动活跃,形成了低层辐合高层辐散的垂直环流机制,这时对流层中部500hPa欧亚环流形势相对稳定,乌拉尔山的长波脊和中亚低槽维持,偏强、偏北、偏西的副热带高压外围偏南气流为该区域输送了大量的水汽,从而形成了陕西及西北地区东部持续的连阴雨天气;当西风带中纬度新疆高压脊建立,副热带高压东移南退时,陕西及西北地区东部的连阴雨天气结束。
Analysis is undertaken of spatial-temporal distributions of autumn rainfall over Shaanxi in 2003, as well as the synoptic and thermal features of atmospheric circulation, indicating that the fallout zones and time are relatively concentrated, rainfall intensity is great and duration is prolonged, which is the most severe event ever observed since 1954. In the transition from a summer to a winter pattern of circulations, with upper troposphere westerly jet moved southward to 400N, areas on the northeast side of the Tibetan Plateau including eastern NW China in which is located Shaanxi are under the control of upper - air divergence to the south of the jet and the areas have high temperature and rich moisture in lower levels, answerable for active rising motion, leading to a mechanism for lower-convergence and higher-level divergence. At this time a relatively stable situation is kept for 500 hPa circulations over Eurasia. A stronger and more eastern and western subtropical high has its outer-region southerly flows responsible for transporting large amounts of vapor, thus leading to a spell of continuous overcast and rainy weather in the northwest part of the country, which comes to an end when a midlatitude Xinjiang high is established and the subtropical high moves eastward and retreats toward the south.
出处
《应用气象学报》
CSCD
北大核心
2005年第4期509-517,共9页
Journal of Applied Meteorological Science
基金
国家973项目(2004CB720208)
中科院知识创新项目(KZCX3-SW-339)
科技部重大基础研究专项(2003CCC01500)
陕西省气象局科研项目(2004M-8)资助
