Comparative Analysis of Two Severe Sandstorm Events in Gansu

Based on the basic observations and automatic hourly data as well as the initial field of numerical prediction of T639,two typical severe sand storm weather processes which occurred on March 19,2010 and April 28,2011 in Gansu were analyzed by using the synoptic and climate diagnostic methods from aspects of the circulation situation,and single station ground meteorological elements,jet stream, vertical speed,stability and so on. The results show before the two sanstorm processes there were nearly similar climatic backgrounds with higher temperature and less precipitation. The circulation patterns of the two sanstorm processes were baroclinic trough and strong front zone at the upper level,strong cold high pressure on surface layer and Mongolia cyclone ahead of front or thermal low. The configuration of high and low air jet and the evolution of surface meteorological elements had some some indication to sandstorm weathers. But because of difference of path and intensity of cold air during the two sandstorm process,the influences were also different.