###
气象:2011,37(7):802-813
本文二维码信息
码上扫一扫!
复杂地形下雷暴增强过程的个例研究
(1.中国气象科学研究院,北京 100081;2.中国气象局北京城市气象研究所,北京 100089;3.北京市气象局,北京 100089)
Intensifying Mechanism of the Convective Storm Moving from the Mountain to the Plain over Beijing Area
(1.Chinese Academy of Meteorological Sciences, Beijing 100081;2.Institute of Urban Meteorology, CMA, Beijing 100089;3.Beijing Meteorological Service, Beijing 100089)
摘要
图/表
参考文献
相似文献
本文已被:浏览 1650次   下载 1485
投稿时间:2011-03-17    修订日期:2011-04-21
中文摘要: 本文基于多普勒雷达变分同化分析系统(VDRAS)反演的对流层低层热力和动力场,并结合多种稠密观测资料,对北京地区2009年7月22日一次弱天气尺度强迫下雷暴在山区和平原增强的机理进行了较深入的分析。研究结果表明:雷暴过程受大尺度天气系统影响不明显,对流前期地面弱冷锋,是此次雷暴新生的触发机制,高层冷平流、低层偏南暖湿气流的稳定维持和对流不稳定能量的聚集是本次雷暴增强的必要条件。雷暴从河北北部移进北京西北山区后,在下山和到达平原地区时,经历了两次明显的发展增强阶段。雷暴第一阶段下山增强,地形强迫起着主要作用,具体表现在三个方面:(1)地形斜坡使得雷暴冷池出流下山加速与稳定维持的偏南气流形成了强的辐合区;(2)地形抬升使得偏南暖湿入流强烈地上升,从而加剧了对流的发展;(3)地形抬高了冷池出流高度,使得出流与近地面偏南气流构成随高度顺转的低层垂直风切变,低层暖空气之上有冷平流叠加,使得雷暴前方的动力和热力不稳定增强。雷暴第二阶段在平原地区再次增强的主要原因是:组织完好的雷暴到达平原地区后,其冷池与低层暖舌在城区(朝阳地区)的对峙,产生了强的扰动温度梯度;强的冷池出流与势力相当的偏南暖湿气流相互作用产生了强的辐合上升气流,并与下沉气流在较长时间内共存;冷池出流形成的负涡度与低层切变产生的正涡度达到近似平衡状态。运用RKW理论,三者导致雷暴前方低层的辐合抬升最强,最有利于雷暴的维持发展。
Abstract:A particularly challenging event occurred on 22 July 2009 in Beijing area. The convective storm moving from the mountain to the plain suddenly intensified as it approached the foothills, and then intensified again as it moved onto the plains. Based on the four dimensional Variational Doppler Radar Analysis System (VDRAS), this paper presented a deep investigation focusing on the intensifying mechanism of the convective storm under weak synoptic scale forcing over Beijing area using Doppler radar, wind profile, surface observation, 4 times daily radiosonde and NCEP data. Results have shown that: The weak cold front triggered the convective storm. The thermodynamic unstable condition including warm, humid, low level southerly wind and significant accumulation of the convective available potential energy (CAPE) indicated by the sounding over plain, and the significant dynamic instability with strong low level vertical wind shear indicated by the wind profiler provided the favorable local environment for the intensification of the storm. In the first intensification stage, the terrain forcing played a dominant role, including: (1) acceleration of cold pool outflow whose kinetic energy drived from potential energy, leading to strong down flow and strong convergence; (2) uplift of south warm moist air flow at the south of piedmont, resulting in a strong upward motion; (3) lifting of the thunderstorm cold pool outflow, which formed strong low level vertical wind shear between north outflow at the low level and south air flow on the surface and led to cold advection over the warm and moist southerly flow, thus enhanced both the dynamic and thermodynamic instability in front of the storm. The second intensification of the thunderstorm in the eastern urban area, was mainly caused by the presence of the strong perturbation temperature gradient zone in the boundary layer in Chaoyang District, resulting from the confrontation of the cold pool outflows of the well organized thunderstorm and the low level warm tongue, and the balance between positive and negative vorticities. The intense updrafts pushed by the interactions between the cold outflow and the warm moist southerly flow, coexisted with the downdraft at the rear of the thunderstorm for a long time. The negative vorticity due to the vertical inhomogeneity of the outflow, was balanced with the positive vorticity due to the vertical inhomogeneity of the environmental flow. According to the RKW theory, this equilibrium state was very favorable for the formation of vertical updraft so that maintained the storm and led to the second intensification.
文章编号:     中图分类号:    文献标志码:
基金项目:公益性行业(气象)科研专项“京津冀城市群强对流天气短时临近预报关键技术研究”(GYHY200706004)和国家自然科学基金面上项目“北京MCS椭圆形暴雨云团的组织化机理研究”(41075047)共同资助
引用文本:
陈双,王迎春,张文龙,陈明轩,2011.复杂地形下雷暴增强过程的个例研究[J].气象,37(7):802-813.
CHEN Shuang,WANG Yingchun,ZHANG Wenlong,CHEN Mingxuan,2011.Intensifying Mechanism of the Convective Storm Moving from the Mountain to the Plain over Beijing Area[J].Meteor Mon,37(7):802-813.