梅汛期区域性暴雨的多尺度分析及临近预警

利用常规观测数据、NECP1°×1°逐6 h再分析资料、FY2E卫星黑体亮度温度TBB资料以及南京、常州多普勒天气雷达产品,对2012年江苏出梅之前的最后一场区域性暴雨过程进行多尺度分析。在此基础上,探索该类暴雨的临近预警线索,结果表明:(1)此次过程的雨带呈准纬向分布,属于典型的梅汛期静止锋降水。过程中主要有两次降水集中时段,两个阶段的降水性质存在差异,但都具备较高的降水效率。(2)中高纬大范围稳定的阻塞形势,为此次持续性暴雨过程的产生提供了有利的大尺度环流背景。而在此过程中,两段降水集中期的形成与地面触发系统的出现和维持有着较为密切的联系。(3)此次过程中两段降水集中期内的物理量特征以及TBB的演变情况和其对应的降水特征存在异同。(4)雷达特征分析表明,此次过程具有较高的降水效率和较长的持续时间。实际业务工作中可以通过判断回波的质心高度和边界层风速有无跃增来估计降水效率的潜势。当推断较高的降水效率潜势将持续较长时间时,应及时发布暴雨警报。

Multi-scale analysis and nowcasting of a regional rainstorm during Meiyu period

By using the conventional observation data, NCEP 1°×1° reanalysis data at 6 h intervals, FY2E satellite T_BB data, as well as the Doppler radar products from Nanjing and Changzhou, a multi-scale analysis on a regional rainstorm in Meiyu period of 2012 in Jiangsu was conducted and some nowcasting clues about this kind of weather process were found. The results show that (1) the weather process can be judged as a typical stationary front precipitation in Meiyu period, based on the quasi-zonal rain band distribution. Although two precipitation periods appear in succession and they are characterized differently, both of them are highly efficient precipitations. (2) A wide range of stable blocking situation in mid-high latitude provides a suitable large-scale circulation background for the production of this process. In this process, the emergence and maintenance of the ground triggerring system are associated with the two precipitation centralized periods. (3) There exist some differences and similarities in the physical characteristics as well as the temporal evolution of T_BB and its corresponding precipitation characteristics in the two precipitation centralized periods. (4) The analysis of radar signal characteristics shows that this process has high precipitation efficiency and lasts for a long time. In practical business work, the potential precipitation efficiency can be estimated through the height of radar echo quality core and enhancement of the boundary layer wind speed. When high precipitation efficiency potential lasts longer, the rainstorm alert should be released timely.