长江中下游地区一次春季暴雨过程的多普勒雷达速度特征分析与研究

Analysis on Characteristics of Doppler Radar Velocity in a Heavy Rain Process in Spring in Mid-and Lower-Reaches of Yangtze River Basin

利用南京多普勒天气雷达径向速度数据,对2012年春季南京地区首场暴雨过程进行了分析。结果表明,风廓线产品(VWP)在降水各阶段都呈现出相应的图像特征:中上层降水云系向下扩展而同下层降水云系"连接",形成"ND"楔形区域,是降水即将开始的一个信号;降水发展阶段大风区底高变化与雨势有较好的对应关系,大风区底高持续下降并维持某一高度后的30 min内,雨势增强明显,随着大风区底高的快速升高,雨强也迅速减弱。降水末期中层"ND"的出现预示着降水云系逐渐消散,风向杆位置的连续下降预示着降水即将减弱停止。逆风区断裂位置及边缘地带对应着强降水的落区。由雷达基数据计算出的平均散度信息较好地反映了此次降水的动力学特征。

The first heavy rain process in Nanjing in spring of 2012 was analyzed by using the Nanjing Doppler radar radial velocity data.The corresponding image features of VWP products are shown during the precipitation process: When the 'ND' area in VWP images presents a wedge shape and the formation of precipitation cloud system on the eve of middle layer is finished and decreased quickly,it means the coming of rainfall;There is a good relationship between the changes of gale base height and precipitation intensity.The precipitation intensity is obviously enhanced in half an hour when the gale base height continues to decline and maintains at a fixed height.The rain intensity decreases rapidly with the gale height shrinking rapidly.The appearance of the middle'ND' area heralds the precipitation cloud system is about to collapse.The continually decline of the position of the rod indicates the end of the rain.The fracture zone and the edge of the AWR are corresponding to the heavy rain area.The divergence information calculated by the radar data reflects the dynamic characteristics of this precipitation process.The qualitative and quantitative analysis on radar radial velocity fields is helpful to capture the precursory characteristics of precipitation,and will offer indicative forecast information.