2009年4月下旬蒙古气旋型大范围沙尘暴天气过程的诊断分析

本文利用卫星资料、加密实况观测资料、NCEP再分析资料分析了2009年4月下旬我国北方地区大范围沙尘天气过程的成因，并对热力、动力及不稳定层结等条件作了物理量诊断，得到了以下主要结论：贝加尔湖阻塞高压、高空冷涡及蒙古气旋是造成此次大范围沙尘天气的有利环流形势，其中蒙古气旋是关键影响系统；干暖舌位置对于沙尘落区有一定指示意义，沙尘暴落区与干暖舌的位置及移动方向一致；高空急流的发展演变与此次沙尘天气密切相关，沙尘天气主要发生在高空急流入口右侧，高空急流加强东移南压对应着沙尘天气东扩南压加强；螺旋度反映出沙尘暴过程中气旋区旋转上升明显，且螺旋度大值区后倾；理查逊数下降并维持低值、风垂直切变增大，大气层结不稳定，易激发沙尘暴发生和向下游传输。

Diagnosis and Analysis of a Large-scale Sand-Dust Storm Process Resulted by Mongolia Cyclone during Late April 2009

In this paper, according to meteorological satellite data, the dense observation and NCEP/NCAR re-analysis data, the reason of the large-scale sand-dust storm process is analyzed over North of China during late April 2009.The dynamic, thermodynamic and stratified unstable conditions of the process are diagnosed. Baikal blocking, high-level cold vortex and Mongolia cyclone are propitious to the dust-sand storm, and Mongolia Cyclone is the key. Dry and warm tongue indicated the fall area of dust-sand storm, because location of the tongue is consistent to the fall area. The development of upper jet flow is closely related to the dust storm. The storm weather mainly occurred in the right of inflow area of upper jet. With the jet moving southeastward and intensifying, the sand-dust weather extended southeastward and enhanced. The helicity reflects the revolving and ascending in cyclone area during the process, and the great helicty tilted backward. Richardson Number and vertical wind shear are important to sand-dust storm. It is easy to make for the occurring and transferring of sand-dust storm that Richardson Number declined and kept low value, vertical wind shear enlarged, and atmosphere was stratified unstable.