引发强沙尘暴的蒙古气旋的动力特征分析

对造成2002年4月5—9日东亚地区一次引发强沙尘暴天气过程的蒙古气旋发生发展过程进行了动力学分析。结果发现,这次气旋发展发生在斜压区中,500 hPa涡度平流和对流层下部的温度平流、大气加热率均对气旋的发生有贡献;气旋的发展阶段以温度平流为主,在气旋发展最强盛阶段对流层下部温度平流的作用大于其他项;气旋减弱阶段大气加热率所起的作用占主导地位,涡度平流和温度平流作用较小;Q矢量锋生函数分析表明大气斜压性的作用不可忽视。位涡的垂直输送作用明显,并形成了对流层内的垂直位涡柱。在气旋的发生发展过程中,始终伴有高空急流,它不仅有利于气旋的发展,同时还激发了低空急流的出现,因此引发该次强沙尘暴的蒙古气旋发生发展过程中对流层内有高低空急流耦合作用。

Dynamical Characteristics for a Mongolia Cyclone Associated with Sand-Dust Storm in North China

The dynamical characteristics were investigated for the development process of Mongolia cyclone related to a severe sand-dust storm event which occurred in East Asian during 5-9 April 2002. The results show that there was obvious baroclinic forcing in the processes of the formation and the development of the cyclone. The vorticity advection at 500 hPa level and the thermal advection and atmospheric heating rate from 1 000 hPa to 500 hPa level were important factors; the main contribution to the intensification of cyclone came from the thermal advection, the action of thermal advection in the lower troposphere was greater than the others when the cyclone reached peak intensity phase; the effect of atmospheric heating rate accounted for dominant status while the cyclone was weakening, but the effect of vorticity advection and thermal advection was secondary; Q vector frontogenesis function further indicated that the function of the atmospheric baroclinicity could not be overlooked. The vertical transport of potential vorticity is significant. In addition, the two maxima of IPV from upper and lower troposphere, respectively, merged to each other when the peak of cyclone intensity appeared. High level jet happened in the origination and development processes of the cyclone all the time, which not only favored the development of the Mongolia cyclone, but also triggered the low level jet; it implied that there is coupling between high level jet and low level jet in troposphere during the developing process of the cyclone.