Analysis on a Sandstorm Event over the Hexi Corridor on April 4～6,2006

Based on the observed data,a severe sandstorm event occurred over the Hexi Corridor in Gansu Province on April 4～6,2006 was analyzed in this paper.The conclusions are as follows: The sandstorm event occurred under the conditions of less rainfall,high temperature and frequent invasion of cold air mass from the arctic area.The mesoscale shear line and the cold front of Mongolia cyclone were the main causes resulting in the sandstorm,and the upper-air jet flow also played an important role in the development of the sandstorm.There was an air convergence in lower-air layer and an air divergence in higher-air layer when the sandstorm occurred.The sandstorm occurred over the area on right front of outlet of the upper-air jet flow at 200 hPa and near the positive vorticity advection center at 500 hPa.The sandstorm event occurred under the conditions of air convective instability and high energy.