2016年长江中下游地区一次暴雨过程诊断分析

A Diagnostic Analysis of Heavy Rain over Middle and Lower Reaches of Yangtze River in 2016

采用美国气象环境预报中心和美国国家大气研究中心(NCEP/NCAR)提供的一日4次的FNL资料和中国气象局自动站与CMORPH融合降水资料,采用非地转湿Q矢量和z-螺旋度等方法对长江中下游地区暴雨过程进行了诊断分析,结果表明:西南涡暴雨产生之前,大气层结不稳定,高层辐散抽吸作用强大,低层辐合,对流上升运动发展剧烈,不稳定能量大量释放,是暴雨天气产生的有利条件。非地转湿Q矢量散度对未来12 h降水落区有较好的指示意义,对流层中低层湿Q辐合区对应降雨落区,暴雨中心与辐合中心基本重合。非地转湿Q矢量的辐合强弱可直接影响上升运动的剧烈程度,湿Q辐合越强,降雨强度越强,所持续时间较长,湿Q矢量是诊断分析降雨落区的重要工具。z-螺旋度强度越大,降水强度越大。在有利的高空槽脊形势和低涡剧烈发展下,主要降水区一般位于z-螺旋度正值中心偏东地区。

Using the FNL global analysis data provided by NCEP/NCAR and the hourly CMORPH precipitation data provided by China Meteorological Administration, a heavy rain case over middle and lower reaches of Yangtze river was studied by wet Q-vector and z-helicity. The results show that the atmospheric is unstable before the occurrence of the southwest vortex rainstorm;the divergence in the upper layer are strong and the convergence in the lower layer is also intense;meanwhile, the convection strong develop;and the unstable energy released sharply, which are favorable for the occurrence of the rainstorm. The wet Q-vector divergence has a good indication for the next 12 h precipitation. The wet Q-convergence area in the middle and lower troposphere are consent to the rainstorm area, and the rainstorm center is basically coincident with the convergence center. The convergence intensity of wet Q vector can directly affect the intensity of vertical motion. The stronger the convergence of wet Q vector is, the stronger the rainfall intensity will be and the longer the duration can be found. Wet Q vector is an important tool for the diagnosis and analysis of rainstorm. Moreover, the greater the intensity of z-helicity is, the greater the intensity of precipitation was found. Under the favorable high trough ridge situation and the rapid development of low vortex, the main falling-water area is generally located in the east of the z-helicity positive center.