北京“7.10”暴雨<i>β</i>-中尺度对流系统分析

何立富; 陈涛; 周庆亮; 李泽椿

北京“7.10”暴雨β-中尺度对流系统分析

国家气象中心, 北京 100081

资助项目:

国家重点基础研究发展规划顶目 P40475030

中国气象局新技术推广预报员专项 MATG2006Y01

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出版历程
- 收稿日期: 2006-03-20
- 修回日期: 2007-03-12
- 刊出日期: 2007-10-31

The Meso β-Scale Convective System of a Heavy Rain Event on July 10, 2004 in Beijing

National Meteorological Center, Beijing 100081

摘要

摘要: 采用NCEP/NCAR再分析资料、自动站加密观测资料、逐时云顶亮温TBB资料、多普勒雷达资料以及成功模拟基础上的高分辨率模式输出资料，对2004年7月10日北京突发性暴雨过程β-中尺度对流系统的发生发展、结构与成因进行了综合分析。结果表明：此次过程影响系统为β-中尺度对流系统，它发生在大尺度暖脊之中，对流层中层的短波槽以及低层西风槽前西南气流与暖切变线北侧东南气流的汇合为其发生提供了良好的环境条件；该β-中尺度对流系统由两个对流云团合并而成，具有椭圆形结构特征，其水平尺度为150 km×100 km，时间尺度约为5 h；低层流场上它表现为中尺度辐合线或强辐合中心，雷达回波和径向速度场所反映的中尺度回波带和辐合线与它的演变有密切关系；在发展强盛期，β-中尺度对流系统具有较强的斜压性特征，垂直倾斜的上升气流及其两侧有明显的下沉补偿气流，显示它具有对流型风暴结构特征；在强对流不稳定层结条件下，700 hPa以下对流层低层具有明显的假相当位温θ_se暖湿舌，近地面层偏南风与偏东风两支气流的辐合及冷空气的侵入，导致行星边界层内能量锋区的加强，从而有利于β-中尺度对流系统发生发展。
- β-中尺度对流系统;
- 暖切变线;
- 斜压性;
- 对流型风暴
Abstract: An analysis on the meso β-scale convective system of a heavy rain event on July 10, 2004 in Beijing is performed by using the special observational data, including automatic meteorological stations data, radar images and satellite images and NCEP/NCAR reanalysis data on the basis of successful simulation. It is found that the heavy rainfall process is generated by a meso β-convective system which is produced in a large scale warm area. The short wave trough in the mid level of troposphere, the convergence between the southwest air current from west wind trough and the southeast air current from the north part of warm shear line in low troposphere provide a good background condition. The meso β-scale convective system is formed by the mergence of two meso-scale convective clusters, it shows an ellipse shape structure of a horizontal scale of 150 km×100 km and the time scale of about 5 hours. It shows the features of the meso-scale convergence line(or convergence center)in low levels stream fields during its occurrence and development stage, and the strong meso-scale convective clouds echo band and meso-scale convergence line exhibited in radar reflectivity image and in radar velocity fields are often related with the occurrence and the development of the meso β-scale convective system. During the stage of strong development, the meso β-scale convective system shows strong baroclinity perpendicular features and has a similar structure of slantwise updraft current to convective storm. Its occurrence and development are forced by the meso-scale convergence line of low troposphere in strong convective instability condition and a warm tongue below 700 hPa. The convergence between the southern air current and eastern air current and the invading of the cold air in the boundary layer lead to the strengthen of the energy front, which is helpful to induce the generation of the meso β-scale convective system.In addition, the cloud top infrared brightness temperature(TBB)of the meso β-scale convective system that induces the heavy rain on July 10, 2004 in Beijing is at-45 ℃ or so, and the updraft airflow reaches the height of around 300 hPa, which means in this case the convection is only activating in the low level of the troposphere in contrast with the deep convective systems of meso β-scale convective system in the mid and lower reaches of Yangtze River and South China, which symbolize with infrared brightness temperature between-70 and-85 ℃, and the updraft airflow reaches the top of troposphere. Future research is needed on whether this conclusion is characteristic for popular convective heavy rain process in North China.
- meso β-convective system;
- warm shear line;
- baroclinity;
- convective storm

HTML全文

图 1 2004年7月10日14:00 500 hPa位势高度场(单位:dagpm)(a)和850 hPa风场(b) (加粗线为槽线, 虚线为切变线)

Fig. 1 The geopotential height of 500 hPa(unit:dagpm)(a)and wind field of 850 hPa(b)at 14:00 on July 10, 2004(solid thicken line is for the rough, dashed line is for the shear)

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图 2 2004年7月10日13:00—20:00的TBB分布

(单位:℃; 阴影为T BB低于-32 ℃)

Fig. 2 The infrared brig htness temperature during 13:00—20:00 on July 10, 2004

(unit:℃; shaded areas denote infrared brightness temperature below-32°)

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图 3 2004年7月10日08:00至11日08:00华北地区24 h降水实况(a)和模拟结果(b)(单位:mm)

Fig. 3 The precipition from 08:00 on July 10 to 08:00 on July 11 in 2004(unit:mm) (a)observation,(b)simulation

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图 4 2004年7月10日17:00对流层低层流场

(a)700 hPa,(b)850 hPa

Fig. 4 The stream field at 17:00 on July 10, 2004

(a)700 hPa,(b)850 hPa

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图 5 2004年7月10日17:00过北京(39.75°N, 116. 25°E)各要素垂直剖面图(a)相对涡度(单位:10^-5s^-1), (b)水平散度(单位:10^-5s^-1),(c)垂直速度(单位:m/s),(d)水平速度v和100倍垂直速度w合成的垂直环流

Fig. 5 Meridion-height cross section of relative vorticity(unit:10^-5s^-1)(a), horizontal divergence(unit:10^-5s^-1)(b)along 39.75°N, zone-height cross section of vertical velocity(unit:m/ s)(c), vertical circulation composed by meridional wind and vertical velocity amplified by 100 times(d)along 116. 25°E

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图 6 2004年7月10日08:00沿116.25°E的θ_se经向垂直剖面(单位:℃)

Fig. 6 Meridion-height cross section of θ_se along 116.25°E at 08:00 on July 10, 2004(unit:℃)

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图 7 2004年7月10日14:00—18:00逐时地面加密观测的气温演变(单位:℃)和地面流场(a)14:00, 气温,(b)14:00, 流场,(c)16:00, 气温,(d)16:00, 流场,(e)18:00, 气温,(f)18:00, 流场

Fig. 7 The hourly surface temperature(unit:℃)and stream field from 14:00 to 18:00 on July 10, 2004 from intensified observations(a)14:00, temperature,(b)14:00, stream field,(c)16:00, temperature, (d)16:00, stream field,(e)18:00, temperature,(f)18:00, stream field

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图 8 2004年7月10日14:00—18:00整层积分的水汽通量散度(单位:10⁶g·cm^-2·hPa^-1·s^-1)(a)和14:00海平面气压(实线, 单位:hPa)与温度(虚线, 单位:℃)(b)

Fig. 8 T he divergence of water flux integrated from bottom to 400 hPa during 14:00—18:00(unit:10⁶g·cm^-2·hPa^-1·s^-1)(a), the sea level pressure(solid line, unit:hPa)and the temperature at 14:00(dashed line, unit:℃)(b)on July 10, 2004

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