一次飑线大风的多资料天气过程分析

Multi-data Weather Process Analysis of a Squall Line Gale

利用高空与地面观测资料、多普勒天气雷达与风廓线雷达资料对一次大风天气过程进行分析。200 hPa高层先辐合后转辐散、500 hPa呈现两槽一脊稳定环流型,东北冷涡分裂小槽引导冷空气南下,使高空槽不断南压。700 hPa有切变线过境,850 hPa有两切变线合二为一,925 hPa存在辐合线。从散度场上看出高层、近地层辐合,中层辐散的散度场形势,配合上冷下暖、上干下湿的条件性不稳定形势,以及高低空系统(切变线、地面辐合线)的触发有利于此次飑线大风天气的出现。雷达观测表明本次过程中,大风区雷达径向速度出现速度模糊,并在多仰角长期存在逆风区,具有较小的VIL值、有界弱回波区。从风廓线雷达观测上分析得出:700 hPa切变线过境是造成动量下传的影响因子之一,中低层至近地面层的风向一致有利于动量下传。

Using high-altitude and ground observation data,Doppler weather radar and wind profile radar data to analyze a gale weather process.At 200 hPa,the upper layer first converges and then turns to divergence.The 500 hPa presents a stable circulation pattern of two troughs and one ridge.The split trough of the northeast cold vortex guides cold air to the south,making the upper trough continue to press south.There is a shear line crossing at 700 hPa,two shear lines at 850 hPa merge into one,and there is a convergence line at 925 hPa.From the divergence field,we can see the high-level and near-surface convergence,the middle-level divergence of the divergence field situation,in conjunction with the conditional unstable situation of cold upper and warm,dry upper and wet lower,and the high and low altitude system(shear line,ground). The triggering of the convergence line is conducive to the appearance of the squall line.Radar observations show that in this process,the radar radial velocity in the windy area has speed ambiguity,and there is a long-term upwind area at multiple elevation angles,with a small VIL value and a bounded weak echo area.From the analysis of wind profile radar observations,it is concluded that the 700 hPa shear line crossing is one of the influencing factors that cause momentum downward transmission,and the consistent wind direction from the middle and low layers to the near-surface layer is favorable for momentum downward transmission.