新疆春季两次直升机积冰气象条件分析

Meteorological Conditions of Two Cases of Aircraft Icing in Spring in Xinjiang

利用卫星、雷达、探空、地面等观测资料和NCEP再分析资料,以及数值模拟结果,对2018年3月新疆昌吉地区两次飞机积冰探测试验过程的云系特征和积冰气象条件进行了分析。结果表明:两次直升机积冰过程影响系统分别为500 hPa低涡和500 hPa浅槽,地面有冷锋配合。积冰时段处于低涡系统发展前期阶段和低槽系统发展中期阶段。积冰云层均为中低云云层,云顶高度为4 km,云顶温度为-15~-25℃,云底高度为1.5 km,云层厚度为1~3 km,光学厚度大于12,雷达回波特征不明显,无回波或者回波强度在10 dBZ以下。3月27日浅槽锋面过程云顶有逆温。CPEFS模式模拟云微观结构表明,积冰云层是以过冷水为主,冰相粒子含量很少。根据直升机特性修改后的CIP初始积冰潜势算法较好地体现了这两次层积云飞机积冰特征,对于稳定性云层的积冰潜势具有指示意义。结合飞行速度等参量计算的积冰强度与实况基本吻合。

Two tests of aircraft icing observation were conducted on March 2018 in Xinjiang in northwest of China.This article studies the icing weather conditions using observations of satellite,radar,soundings,NCEP reanalysis data and simulations by the WRF mesoscale model coupled with CAMS cloud scheme.The results suggest that the major weather systems of the two icing cases were the vortex and the shallow trough at 500 hPa separately,accompanied by the cold front on the surface.The icing time was in the early stage of the vortex system and the middle stage of the shallow trough system.The icing clouds were both low and middle clouds.The cloud top height was about 4 km and the cloud top temperature was-15 to-25℃.The height of cloud base was 1.5 km and the cloud thickness was 13 km.The optical thickness was larger than 12 and the radar reflectivity was less than 10 dBZ.There existed a temperature inversion layer on the cloud top during the shallow trough process on 27 March.The microphysical structures simulated by the CPEFS model show that the icing cloud was composed of large number of supercooled water and few ice particles.The results by the CIP initial icing potential algorithm can basically reflect the icing characteristics of the two cases and can indicate the icing potential of stable clouds.The icing intensity calculated through combining flight speed of helicopter and other parameters is basically consistent with the actual situation.