江西局地冰雹WebGIS雷达拼图回波特征分析

Echo Characteristic Analysis of WebGIS Radar Mosaic on Hailstone in Jiangxi

使用MICAPS系统平台、江西强天气监测平台、江西雷电监测平台、江西WebGIS雷达拼图平台等数据,采用形态分析方法,对2018年3月14日和4月5日井岗山、瑞昌、永修局地冰雹进行分析,结果表明:局地冰雹往往由超级单体回波所为,其影响范围较小,冰雹直径为5~10mm,降雹时间约30min。500hPa、700hPa和850hPa有较强的暖湿西南急流,低层湿舌向东北伸展,地面有冷锋过境或存在辐合线,是强天气发展加强的重要天气系统。弓状回波带向前突出部分的前方有对流单体回波产生并且逐渐靠拢时,会使前方单体回波发展成为超级单体回波结构而产生冰雹等强天气。回波的合并是与回波的“传播”相联系的,回波的传播方式一方面加快了回波的移动速度,另一方面改变了回波的移动方向。局地冰雹回波产品特征:强度达到60~65dBz、回波顶高ET达到9~12km、液态含水量VIL达到40~60kg·m-2、垂直显示方式RHI上55~60dBz强回波顶高达到5~6km、有虚假回波伴随或有不特别明显的悬挂回波结构等特征。江西WebGIS雷达拼图上对冰雹等强天气的监测更为直观、明显,在识别冰雹回波上有较好的指示:短带回波中心强度从55~60dBz发展为60~65dBz时地面开始降雹;超级单体回波由55~60dBz发展为60~65dBz时预示着可能出现冰雹等强天气。冰雹的预报着眼点就是根据WebGIS雷达拼图上的以下特征来把握:1)60~65dBz(粉红色)回波范围大于10×10km,回波形状呈椭圆形;2)40dBz(橘黄)回波界线与65dBz回波界线梯度大;3)60~65dBz回波中心有65~70dBz(紫色)回波“核”;4)强回波下风向有“前伸”回波结构。

using the data of MICAPS system platform, Jiangxi strong weather monitoring platform, adopting morphological analysis method Jiangxi lightning monitoring platform, Jiangxi WebGIS Radar Mosaic platform and other data, the local hail which occurred in Ninggang, Ruichang and Yongxiu on March 14 and April 5, 2018 is analyzed. The results show that the local hail often comes from the supercell echo, its influence scope is often smaller. The diameter of hail is 5 10 mm, and hail time is about 30 min. While there are strong warm wet southwest jet at 500 hPa, 700 hPa and 850 hPa, low layer wet tongue stretches to the northeast, and a convergence line or cold front crossing on the ground, it is favorable to the develop of strong weather. When the echoes are generated and converged in front of the forward protruding part of bow echo, the echo will develop into a supercell echo structure and produce hail or other strong weather. The merging of echoes is associated with the “propagation” of the echoes. The propagation mode of echo accelerates the moving speed of the echo on one hand, and changes the direction of the echo movement on the other hand. The echo features of local hail are as follows. The intensity reaches 60 65 dBz, the echo top (ET) is 9 12 km, the vertical integrated liquid water content (VIL) is 40 60 kg·m -2 , the strong echo top of the 55 60 dBz is up to 5 6 km on the vertical display (RHI), and there is false echo accompanied or no obvious suspension echo structure. The monitoring of hail and other strong weather on the Jiangxi WebGIS Radar Mosaic is more intuitive and obvious. It has a good indication of the hail echo recognition: the hail begins when the intensity of the short band echo center is from 55 60 dBz to 60 65 dBz, and the hail or other strong weather may appear when the supercell echo is developed from 55 60 dBz to 60 65 dBz. The forecast points of hail on the WebGIS Radar Mosaic are characters such as: 1)The range of 60 65 dBz (pink) echo is more than 10×10 km, the shape of echo is elliptical. 2)The gradient of boundary line of 40 dBz (orange) echo and 65 dBz echo (pink) is large. 3)The 60 65 dBz (pink) echo has 65 70 dBz (purple) echo “core”. 4)The strong echo has a “protrusion” structure in downwind direction.