Abstract: The reflectivity fields of Beij ing-Tianjin region during 2005-2007 were classified into convective and stratiform components using an automatic algorithm, and then the vertical profiles and diurnal variation of convective and stratiform echoes in this region were analyzed. The results are as follows. 1) An obvious bright band was in the stratiform profile of Beijing-Tianjin region at about the 4 km altitude. The bright band was strongest in the night local time, while weakest in the morning. 2) In this region, the diurnal variations of both convective area and stratiform area were unimodal. The maximum areas occurred in the local evening, while the minimum occurred near local noon. The variation of stratiform area was about 1-2 hours later than convective area. 3) There were two peaks in the diurnal variation of the ratio between convective and stratiform area. One was associated with the thermal convection in the local afternoon, and the other was connected with the moist mass convection happens in the local evening. Both these two types of convection are tconvective systems in Beijing-Tianjin region.

Key words: weather radar, convective echoes, stratiform echoes, Beijing-Tianjin region

摘要： 利用自动分类算法, 识别出2005?2007 年 5?8 月京津地区雷达回波中的对流性和层状降水回波。在此基础上, 分析了该地区对流性和层状降水回波的垂直廓线和回波面积的 日变化特征。结果表明: 京津地区层状降水回波的垂直廓线在4 km 高度( 0℃) 附近, 出现了明显的 “零度层亮带”, 亮带强度在当地夜间最强, 当地上午最弱;该区域内, 两种类型的回波面积均呈明显的单峰型日变化特征, 面积峰值出现在当地夜间, 在当地午间面积最小;层状降水回波面积的变化比对流性降水回波的变化滞后了 1 ～2h; 对流性回波与层状回波面积比的日变化存在两个明显的峰值, 分别对应两类影响京津地区的主要对流系统: 午后出现的热对流和具有夜发性的湿对流。

关键词: 天气雷达, 对流性降水回波, 层状降水回波, 京津地区