2004年辽宁地区一次沙尘天气过程的动力机制分析

利用NCEP再分析资料、气溶胶指数资料和污染物监测资料,从气候背景和环流形势入手,着重探讨了2004年4月14-16日辽宁地区的一次典型沙尘天气过程的形成动力机制.研究结果表明:2004年春季我国北方的气候背景为春季沙尘天气的发生提供了丰富的沙尘源;此次过程中,高空大槽引导极地强冷空气南下,配合低层强大的蒙古气旋构成了东北地区沙尘过程的典型天气环流形势.在起沙的动力机制方面,高低空急流的耦合加速了低层的辐合上升运动,加速了低层的辐合上升运动,高低空急流的有利配置所触发的强烈上升运动构成此次沙尘过程的主要动力机制.螺旋度上负下正的垂直分布是此次沙尘过程发生发展的重要动力机制,这是由于这种垂直结构对于沙尘过程这种中尺度天气系统而言,构成了低空辐合、高空辐散的深厚上升区,这种螺旋度的垂直分布十分有利于沙尘的发展.

Analysis of the dynamic mechanics of a dust event in Liaoning in 2004

Based on NCEP (National Centers for Environmental Prediction), aerosol index and pollution data, the dynamic mechanics of a typical dust event over Liaoning Province during 14~16 April 2004 are analyzed based on climate and air circulation information. The analysis shows that climactic background of North China in 2004 promoted the dust event. Cold polar air traveled from north to south led by an upper atmosphere trough and the powerful Mongolian depression formed typical dust circulation patterns in north-east China. Considering the dust emission, upper and lower level jet streams formed a pumping effect because of divergence at the upper level, which strengthened the low-level updraft. The strong updraft resulting from coupling between the upper and lower level jet was the main mechanism behind this sand event yet the vertical distribution of helicity was also important, because the vertical structure made a powerful ascending area where the air converged on the upper level and diverged on the lower level. Thus conditions were very favorable to the development of sand storms.