一次爆发性气旋引发东北地区暴雨成因分析

利用2016年5月2—4日NCEP的FNL 1°×1°再分析资料和GDAS的1°×1°再分析资料、地面观测资料,运用天气学分析、等熵位涡、物理量诊断和水汽来源追踪等方法,从大尺度环流背景、水汽源地和输送、动力和热力机制、等熵位涡等方面对2016年春季一次地面气旋爆发性发展导致的东北地区暴雨天气过程进行了分析。结果表明:位于40°N附近的黄淮气旋北上加强发展,2日14时至3日14时中心气压下降24 hPa,超过爆发性气旋的定义标准。500 hPa高空槽快速加强发展为闭合低涡,低空切变线加强发展为低空低涡,其东部形成明显的低空急流,为暴雨区提供水汽和热量,为东北地区典型的暖式切变降水。等熵位涡自320 K高层向305 K低层输送下传,并逐步向南向东移动,高空正位涡的下传促使地面气旋快速发展,上升运动加强,有利于暴雨的出现。比湿在6 g·kg^(-1)以上对东北地区春末夏初暴雨预报有一定的参考意义。水汽主要来源于东海、黄海及西北太平洋。暴雨区与850 hPa水汽通量散度的负值区、700 hPa垂直速度和850 hPa绝对涡度大值区较为一致,强降水区与850 hPa相当位温密集带和暖区锋生区相对应,降水位于能量锋区以及偏暖区一侧。

Analysis of rainstorm caused by an explosive cyclone in Northeast China

Based on the NCEP FNL(National Center for Atmospheric Research Final Analysis) and GDAS(Global Data Assimilation System) 1°×1° reanalysis data, ground observation data from May 2 to 4 in 2016, the rainstorm process in Northeast China caused by the explosive development of the surface cyclone in spring was investigated.The large-scale circulation background, water vapor source and transport, dynamic mechanism, and thermal conditions were analyzed.The results show that the Huang-Huai cyclone locates near 40°N intensified northward and the central pressure drops 24 hPa from 14:00 on February 2 to 14:00 on February 3, exceeding the definition standard of the explosive cyclone.The 500 hPa upper trough is rapidly strengthened and developed into a closed vortex, and the low-level shear line is strengthened and developed into a low-level vortex.The obvious low-level jet forms in the east of the trough, which provides water vapor and heat for the rainstorm area and the rainstorm is typical warm shear precipitation in Northeast China.Isentropic potential vortexes transport downwards from the upper level of 320 K to the lower level of 305 K and gradually move to the southeast.The downward transmission of the upper level positive potential vortexes enhances the development of surface cyclones and the convergence of ascending movement, which is conducive to the increase of rainstorms.The specific humidity above 6 g·kg^-1 will be useful for rainstorm forecasts in late spring and early summer in Northeast China.Water vapor mainly comes from the Northwest Pacific Ocean, such as the East China Sea and the Yellow Sea.The rainstorm area is consistent with the negative area of water vapor flux divergence at 850 hPa, the vertical velocity at 700 hPa, and the absolute vorticity large value at 850 hPa.The strong rainfall area corresponds to the dense zone of equivalent potential temperature at 850 hPa and the warm frontogenic area.The precipitation is located in the energy front area and the side of the warm area.