蒙古气旋产生强沙尘暴的诊断分析

利用MICAPS资料、FY-2C红外卫星云图和2.5°×2.5°NCEP再分析资料,对2008年5月25日至28日大范围沙尘暴过程进行了天气动力诊断和物理量场分析。结果表明,强沙尘暴主要出现在冷平流前的温度梯度密集区和涡度梯度密集、陡峭区。在这次强沙尘暴过程中,暖平流是蒙古气旋发生、发展的重要热力因子,大气热力不稳定和强风是起沙的动力;500 hPa阶梯槽快速东移是飚线产生的触发系统;对流风暴是引发强沙尘暴主要因素。蒙古气旋的发展加大了冷锋前后的气压和温度梯度,为对流风暴的发生提供了热力不稳定条件。700 hPa冷平流爆发性下沉、南下,为强沙尘暴的产生提供了强大动力。

A Strong Sandstorm Produced by Mongolian Cyclone:A diagnostic analysis

By the use of MICAPS data, FY-2C satellite infrared cloud images and 2.5°×2.5° NCEP reanalysis data, dynamics process and physical fields of a large-scale strong sandstorm on May 25—28, 2008 were analyzed. The results showed that the strong sandstorm occurred in dense temperature gradients area before cold advection and dense vorticity gradients area. The warm advection was important thermal factor of the Mongolian cyclone genesis and development during the process of the strong sandstorm, and unstable atmospheric thermal energy and strong winds were the driving forces of the strong sandstorm. The trigger factor for squall line was provided by rapid eastward moving of steps trough at 500 hPa, and convective storm was the main factor triggering the strong sandstorm. Gradients of pressure and temperature before and after the cold front were enlarged by development of the Mongolian cyclone, by which the unstable thermal energy condition was provided for the production of the strong sandstorm. Outbreak sink and southbound of cold advection at 700 hPa provided a powerful driving force for the production of the strong sandstorm.