| 一次冷锋大暴雨过程的多普勒雷达观测分析 |
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| 引用本文： | 张家国,吴翠红,王珏,万玉发.一次冷锋大暴雨过程的多普勒雷达观测分析[J].应用气象学报,2006,17(2):224-231. |
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| 作者姓名： | 张家国 吴翠红 王珏 万玉发 |
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| 作者单位： | 1.中国气象局武汉暴雨研究所, 武汉 430074 |
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| 基金项目： | 湖北省科技攻关项目;湖北省气象局科技发展基金 |
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| 摘 要： | 2003年6月22—23日受冷锋和低空急流影响, 湖北省东部地区出现了一次区域性大暴雨过程。用每6 min一次的武汉多普勒雷达资料, 详细分析了冷锋和低空急流天气系统在多普勒雷达径向速度PPI、速度垂直剖面VCS和速度谱宽产品上的主要特征和演变特点。结果表明:PPI上冷锋对应一条径向速度辐合线, 由于多普勒雷达所测的是径向速度, 辐合线在向雷达站移动过程中出现逐渐“变短”的现象。因在冷锋附近低层的风垂直切变相对较大, 多普勒雷达所测的速度谱宽很大, 这一特征对确定冷锋的位置很有帮助。中尺度低空急流在PPI速度图上表现为有较大径向速度切向梯度的大风核, 且距离雷达站越远这一特征越明显。在上述分析基础上, 还结合地面逐时雨量资料等分析讨论了产生暴雨中尺度对流系统的传播与冷锋和低空急流的关系。
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| 关 键 词： | 冷锋 中尺度急流 暴雨 多普勒雷达特征 |
| 收稿时间： | 2005-01-24 |
| 修稿时间： | 2005-08-29 |
Observational Analysis on a Cold Front Heavy Rain Using Doppler Radar Data |
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| Zhang Jiaguo,Wu Cuihong,Wang Jue,Wan Yufa.Observational Analysis on a Cold Front Heavy Rain Using Doppler Radar Data[J].Quarterly Journal of Applied Meteorology,2006,17(2):224-231. |
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| Authors: | Zhang Jiaguo Wu Cuihong Wang Jue Wan Yufa |
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| Institution: | 1.Institute of Heavy Rain, China Meteorological Administration, Wuhan 4300742.Wuhan Central Meteorological Observatory, Wuhan 430074 |
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| Abstract: | Forced by cold front and low-level jet, a regionally torrential rainfall occurs in the east of Hubei Province during June 22—23, 2003. On 22 June, a synoptic-scale cyclone is developing over the reaches of the Changjiang and Huaihe River. Leaded by the deepening cyclone, the ground cold front moves southward and triggers meso-scale convective system (MCS) when it confronts with southwest low-level jet. The MCS perches on the tail of the comma-pattern cloud system in infrared weather satellite image. The MCS moves southward, strengthens and results in heavy rain in the east of Hubei Province.Wuhan Doppler radar collects the data set during the heavy rain period. The radial velocity and spectrum width features of the cold front and the low-level jet on Doppler radar are analyzed in detail using base velocity, velocity cross section, base spectrum width data collected by Wuhan Doppler radar every six minutes. Also, combining analysis on radar base reflectivity and surface rain-gages data, the synoptic relationships between the spread of the MCS and the cold front, low-level jet are discussed briefly. The results are as follows: ① There is a convergence line corresponding to cold front on base velocity product. Because Doppler radar only detects radial velocity of the wind, the convergence line gets short gradually when it moves towards radar station. Spectrum width is high near the cold front for relatively high vertical wind shear in low level of the troposphere, which helps to determine the position of the cold front. ② The salient features of the meso-scale low-level jet on base velocity product include big radial velocity and big tangent gradient of the radial velocity, and the farther the gale core is apart from radar station, the clearer the big tangent gradient behaves, which is called "great gale core" detected by Doppler radar many times. ③ The MCS that brings regional torrential rainfall is jointly resulted from cold front and low-level jet. At the intense developing stage of the MCS, the strong low-level jet climbs along cold surface front quickly and steeply. At weakening stage of the MCS, rainfall intensity decreases because of lessened gradient of the cold front though there is a divergence flow in troposphere aloft. In addition, the heavy rain occurs near the join point of the cold front and low-level jet and on the left of the jet. As the direction and position of the low-level jet is fixed, the join point can shift to west when cold front moved to south. Accordingly, MCS strengthens in the west of the join point for horizontally cyclonic vortex on the left of the jet, and weakens in the east of it for horizontally anti-cyclonic vortex on the right of it. |
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| Keywords: | cold front low-level jet heavy rain Doppler radar characteristics |
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