摘要
2007年10月5—6日,北京地区在通常干爽的秋季出现了大雨过程。采用WRF模式进行数值模拟和敏感性试验发现,北京这次大雨天气在很大程度上受到东南沿海"罗莎"(0716)台风的远距离影响。主要表现在:(1)台风外围环流波动在对流层顶向北传播,在北京上空与西风带波动叠加,形成对流层上层强辐散;(2)台风北侧东风环流将东海和黄海的水汽汇聚于长江中下游地区,之后沿着副高边缘向北输送至40°N附近的北京地区;(3)受"罗莎"台风影响对流层中低层水汽辐合带向北推移1.5个纬距,形成北京地区的水汽辐合。动力分析显示,北京地区上空对流层500 hPa以下强辐合,500 hPa以上尤其是300～200 hPa强辐散,形成几乎整层的上升运动和600 hPa以下水汽的辐合,对大雨的产生十分有利。此外,大雨期间对流层顶长时间强的冷平流和对流层中低层的暖平流,在一定程度上对降水的维持起到了积极作用。敏感性试验同时表明,没有"罗莎"台风的影响,北京地区上空上述动力条件基本不存在。
In early October 2007, a series of rainfall events successively occurred in Beijing during the normally rainless autumn days, among which was a heavy rainfall event on October 5th and 6th. In this paper, by means Of numerical simulation and sensitivity experiments, we found that this unusual heavy rainfall event in Beijing Was highly affectedby the activities of typhoon Krosa （0716） in the southeast coastal area of China. Results show that the peripheral circulation of typhoon Krosa had a remote influence on this heavy rainfall event. The waves, generated in the peripheral circulation of Krosa, propagated northward at the tropopause and interacted with the westerly trough waves, resulting in strong divergence in the upper troposphere over Beijing. The water vapor from the northern East China Sea and the Yellow Sea was transported to the middle and lower reaches of the Yangtze River by the easterly winds on the north side of Krosa, and then was advected northward to 40 °N around Beijing by the flows of the remnant subtropical high. The moist convergence zone at the middle- and lower-troposphere moved 1.5°northward under the influence of Krosa so that part of the zone was over Beijing. In addition, dynamical analyses indicated that during the event, in the troposphere over Beijing, there were strong convergence below 500 hPa, strong divergence above 500 hPa （especially between 300 and 200 hPa）, ascending motions in the whole troposphere, and moist convergence below 600 hPa. All these conditions are very favorable to heavy rainfall. Moreover, the long-lived strong cold advection at the tropopause and the warm advection at the middle-and lower- troposphere helped to maintain the rainfall to a certain extent. Sensitivity experiments showed that these dynamical conditions can hardly establish without the influence of the typhoon.
出处
《热带气象学报》
CSCD
北大核心
2012年第5期664-674,共11页
Journal of Tropical Meteorology
基金
国家973项目(2004CB418306)
国家重点基础研究发展规划项目(2004CB418306)
国家自然科学基金项目(40975032)
科技部公益性行业科研专项(GYHY200706004)共同资助
关键词
台风
秋季大雨
外围波动
远距离影响
数值模拟
typhoon
autumn heavy rainfall
peripheral waves
remote influence
numerical simulation
