滇西北高原区域性冰雹过程的雷达产品分析

RADAR PRODUCTS ANALYSIS OF A REGIONAL HAIL EVENT IN NORTHWEST YUNNAN PLATEAU

利用丽江新一代天气雷达回波资料并结合常规资料,对2010年7月31日发生在丽江市、维西县的一次强对流天气进行分析。结果表明:青藏高压底部偏东气流强,结合滇西北区域的辐合区及地面冷空气,形成了有利于冰雹天气发生的天气背景;在基本反射率因子图上冰雹云回波单体的强度值都大于50 d Bz,最大值达到63d Bz,其外形结构为"点状";在VCS(Vertical Cross Section)垂直剖面图中冰雹云回波单体的强回波核高度在8km左右,且出现了悬垂状、弱回波区、回波墙等结构特征;逆风区和低层风速的辐合是本次冰雹过程中径向速度场中的主要特点;冰雹指数产品中大三角形的出现可以作为冰雹预警的一个指示性标志;降雹前VIL值都有不同程度的跃增,跃增达到最大值后地面降雹,降雹时的VIL值在23 kg/m2以上,系统减弱后VIL值开始减小。

The severe convection weather occurred in Lijiang and Weixi on July 31,2010 was analyzed by using Lijiang＇s Doppler- Radar（ CINRAD / CC） and conventional meteorological data. The results showthat the hailstorm weather caused by the strong easterlies at the bottom of the Tibetan high and cold air moved to Northwest Yunnan Plateau. Echo intensity of hail cloud was greater than 50 d Bz on radar base reflectivity image,the echo peak value was 63 d Bz. The features of this hail cloud can be found,such as dots structure,overhang echo,weak echo area and echo wall. The main features was that adverse wind region and convergence of wind in lower atmosphere. Triangle have appeared in hail index product is a good indicator of hail alert. Before the hail the VIL have different extended,when it reached to maximum the hail was on the ground and the VIL was bigger than 23 kg / m2.