长江中下游地区梅雨期线状中尺度对流系统分析Ⅰ:组织类型特征

Analysis of the linear mesoscale convective systems during the meiyu period in the middle and lower reaches of the Yangtze River. Part Ⅰ: Organization mode features

利用2010年6—7月长江流域雷达拼图和观测资料,统计分析了长江中下游地区梅雨期中尺度对流系统的类型和活动特征。结果表明,长江中下游地区梅雨期线状中尺度对流系统发生个数比非线状中尺度对流系统发生个数略多,存在8类典型的线状中尺度对流系统:尾随层状降水中尺度对流系统(TS)、准静止后向建立中尺度对流系统(BB)、邻接层状单向发展中尺度对流系统(TL/AS)、前导层状降水中尺度对流系统(LS)、平行层状降水中尺度对流系统(PS)、断裂线状中尺度对流系统(BL)、镶嵌线状中尺度对流系统(EL)、长带层状降水中尺度对流系统(LL)。其中,有6类和已有的研究结果类似,EL中尺度对流系统和LL中尺度对流系统是长江流域梅雨期新统计的两类线状中尺度对流系统。TS、LS、PS和BL等4类中尺度对流系统是移动性的,TL/AS、BB、EL和LL类中尺度对流系统为移动缓慢相对静止的。线状中尺度对流系统平均持续时间大多数在7h以上,TL/AS和TS类持续时间较长。线状中尺度对流系统多形成在长江两岸附近,重庆北部至鄂西沿江地带、江汉平原地区、皖南和赣北地区、大别山地区是中尺度对流系统的多发地;中尺度对流系统移动路径分为东、东偏北、东偏南、南等4种,这与环境场的引导气流有关。长江中下游地区中尺度对流系统发展阶段日变化呈现多峰型特征,在成熟阶段的下午至夜间发生强降水的概率明显大于凌晨至上午。

Using the composite radar reflectivity data and operational observation data, the mesoscale convective system （MCS） that occurred in the middle and lower reaches of the Yangtze River in June and July 2010 are investigated. The numbers of the line-MCS are more than the numbers of the nonline-MCS. There are eight identified classes line-MCS： Trailing stratiform MCS （TS）, Leading stratiform MCS （LS）,Training line/Adjoining stratiform MCS （TL/AS）, Backbuilding/Quasi-stationary MCS （BB）, Parallel stratiform MCS （PS）, Broken line MCS （BL）, Embedded line MCS （EL） and Long line MCS （LL）, and six of them are the same as the previous classifyed archetype, but the embedding line MCS and the long zonal stratiform MCS are the new statistical classes in the middle and lower reaches of Yangtze river during the meiyu period. The TS, LS, PS and BL clas- ses are movable during their life period, while the TL/AS, BB, EL and LL ones are immovable. The average lasting time of the line MCS is greater than 7 hours. The MCSs usually develop along the Yangtze River, with the more frequently occurring areas of the MCS located north of Chongqing city, in the Jianhan plain, south of Anhui Province and over the Dabie mountain. The MCSs move eastward, northeastward, southeastward or southward, and the moving track of the line MCS is related to the steering flow of its environmental field. Diurnal variations of the MCS are of several peaks during its early stages, while in ma- ture stages, the occurring strong precipitation probabilities are distinctly larger from afternoons to nights than from late-nights to mornings.