Numerical Analyses Of Topography Influence And Characteristic Of A Heavy Sand-Dust Storm Event In MinQin

Sandstorm is a hazardous strong severe weather which is the result of the interaction of the bad natural environment and anomaly atmospheric movement. The different areas in the northwest sandstonn occur with local characteristics, MinQin is located on the boundary of Badan Jara and Tenger Desert, and just located on the beneath mountain pass which is fonned by Jas cloth Lai and Longshou Mountain. This advantageous terrain and abundant dust source, plus it is the only way which must be passed of cold air of northwest China, leading to MinQin became the key area of sandstorm occurring in HeXi Corridor.The purpose of this study is to use the actual observation data and GRAPES_SDM sandstorm model, analyzes a particularly strong sandstorm which occurred in MinQin on April 24th 2010, and through the modification of the terrain parameter of the model to make adjustments the surrounding terrain of MinQin, then analyzes the terrain effection in the process of sandstonn.Firstly, based on the live observation data of April 24,2010 to analyse one process of regional strong sandstorm weather which appeared in Minqin in the Hexi Corridor The results show that:1) This heavy dust storm weather mainly touched off by Ural low trough before ridge, high level jet stream, surface thermal pressure and cold front etc, for sand storm,strong temperature gradient and atmosphere baroclinic provided initial energy motion.2) During this heavy dust storm process, Polar dry cold air was transported to the trough under a strongly and northerly airstream which is after Ural trough,so the low trough deepens and frontal zone before trough strengthen, as the pressure and temperature gradient increased resulting in the deep and strong ascending motion which was the large-scale circulation field of the dust storm. Before this heavy dust storm coming, the air temperature rose gradually, relative humidity sharply descend, the surface in thermal low pressure of dry and warm conditions, the wind directions experienced difference phases and increased, the ground temperature also increased; visibility and air temperature sharply decreased during the sandstorm, at the same time,the difference of 3 time-varying pressure rose with the pressure increased, relative humidity increased and the wind speed reached the peak value; after a short time passing, with the long-wave radiation strengthen because of the upper level cold advection and the dust weather weakening, which was leading to the air temperature consecutive drops, relative humidity and visibility increased, the wind speed declined with the little change of directions.3) Beyond that the sandstorm was very much involved with the alteration of vertical velocity and helicity that they could reflect the change of strength of sandstorm.Secondly, using a dust model GRAPES SDM to simulation the terrain filed of this process through three ways of changing terrain and according to the special terrain of MinQin, then mainly analysed by wind speed, surface dust emission, dust transportation and compared to the values of control experiment, the result shows that:1)Firstly found that when lowered terrain level, wind speed of one site was higher than control experiment, this type terrain would weaken the diffusion intensity.2)Secondly the wind speed of site increased with the varying time when heightened the terrain, the spreading of dust storm was changed owing to this terrain.3)Finally, the wind speed obviously increased when removing the terrain, the spreading of dust storm in MinQin and the whole region where the value also declined was weakened but expansion of south and southeast direction compared to the control test.4)During the same time the simulation value of dust emission of three types experiment were less than the control test, and the least one was upraising of the mountain.