摘要
利用NCEP分析资料、云地闪电、卫星、多普勒雷达、风廓线雷达和RASS观测资料，对引发2009年8月6日广州南沙大暴雨的中尺度对流系统的演变和风场垂直结构进行分析，结果表明：（1）此次暴雨的直接影响系统是登陆后重新加强的热带风暴内发生、发展的α-中尺度对流系统，其内若干对流单体及其“列车效应”是导致大暴雨的直接原因；（2）强地闪集中发生在云顶相当黑体温度（TBB）低于-64℃云区和大TBB梯度区内，或40dBZ以上的强回波区及回波梯度大值区，强地闪活动略落后于强降水；（3）风场垂直结构观测表明，α-中尺度对流系统的低层急流有两次加强过程，与低空入流两次增强有直接对应关系；急流轴上多个中尺度脉动及低涡发展与雨强的剧增相对应，其时间尺度为0．5-1．0h，这种风场的中尺度特征正是中尺度对流系统中强上升人流和下沉气流在风廓线雷达观测到风场垂直结构中的反映；（4）边界层的上升运动发生在α-中尺度对流系统的前部，上升运动与地面中尺度低压生成及辐合线有关，中尺度低压和上升运动的出现比强降水提前1h。
The evolution and the wind vertical structure of an MCS for a rainstorm on 6 Aug 2009 at Nansha, Guangzhou are analyzed using the NCEP, in-cloud lightning, satellites, Doppler radars and wind profilers data. The major conclusions are as follows： （1） This torrential rain was caused by a meso-α-scale convective system, which generated and developed in a strengthening tropical storm after landfall, and within the system several convective cells and “train effect” played an important role in the heavy rainfall. （2） Cloud-to-ground lightning flashes mainly occurred in the region where the temperature was less than -64℃ and the TBB gradient was large, or there were echoes that were more than 40 dBZ and large echo gradient. （3） Observation of the wind structure of the MCS shows that there were two strengthening processes of low-level jets which were directly related to two increases in low-level inflow. Several jet pulsations and low vortexes on the jet axis, on the time scale of 0.5-1 h, corresponded to the incidence of surge in rainfall intensity, which was a mesoscale feature that reflected strong updraft and downdraft in the MCS. （4） It is found that vertical upward movement occurred in the front of the meso-α-scale convective system in PBL, which was closely related to the surface mesoscale depression and convergence line, and heavy rain appeared 1 hour after the surface mesoscale depression and convergence line did.
出处
《热带气象学报》
CSCD
北大核心
2015年第3期345-354,共10页
Journal of Tropical Meteorology
基金
广东省气象局创新团队(201002)
中国气象局关键技术集成及应用项目(CMAGJ2014M39)共同资助
