源于飑线前期和强降雨带后期的弓形回波雷达产品特征及预警

Radar Echo Characteristics and Warning of Bow Echoes Evolved from Early Developing Squall Lines and Weakening Linear Heavy Rainstorms

利用多普勒天气雷达探测资料,结合环境物理量和地面中尺度站监测实况,对4次弓形回波的形成与特征及所致灾害性天气现象进行了综合分析,其中这4次弓形回波包含2次产生于飑线发展的前期,2次产生于强降雨带减弱阶段。结果表明,源于飑线发展前期的弓形回波所致大风明显大于源于强降雨带减弱阶段的弓形回波所致大风,前者可致10级甚至以上大风,后者可致9级大风。风暴后部中低层径向速度"异动"现象,即径向速度绝对值迅速增大,预示着风暴后部倾斜下沉气流迅速加强,导致低层反射率因子上出现明显后部入流缺口,从而产生弓形回波。飑线发展前期阶段,其后部中层出现绝对值≥27 m·s^(-1)的径向速度时,比弓形回波形成时问提前18~30 min;强雨带减弱阶段,其后部中低层出现绝对值≥25 m·s^(-1)的径向速度时,比弓形回波形成时间提前6~12 min。

Using CINRAD/SA radar data,combined with automatic weather station and sounding data,the formation and radar characteristics of four bow echoes,and straight-line winds caused by bow echoes were analyzed.Two bow echoes evolved from squall lines in early developing stage,two bow echoes evolved from linear heavy rainstorms in weakening stage.The results show that bow echoes from early developing squall lines can produce severe straight-line winds over 25 m·s^(-1)(10 levels of gales),significantly stronger than the straight-line winds(about 9 levels of gales) caused by bow echoes from weakening linear heavy rainstorms.The abnormal changing of radial velocity or rapidly increasing of the absolute value of radial velocity at middle or low level in the rear of a storm indicate rapidly strengthening of a tilted downdrafts,and will cause the rear inflow notch in low level reflectivity,produce bow echo and damaging straight-line winds.The absolute value of radial velocity ≥27 m·s^(-1) at middle or low level in the rear of a early developing squall line has a 18~30 minute lead time to the formation of bow echoes.The absolute value of radial velocity ≥25 m·s^(-1) at middle or low level in the rear of a weakening linear heavy rainstorm has a 6~12 min lead time to the formation of bow echoes.