【摘要】 利用较成功模拟的一次强沙尘暴过程的MM5模式输出资料进行了动力学诊断研究,计算了动量收支残差X,结果表明,3月19日高低层上,最大X矢量位于河西小槽的后部,表明动量残差主要是加速西北气流的南下。X矢量与风矢量 V的夹角在槽后<90°,这说明动量残差在槽后加速冷空气南下,非常有利于小槽的发展和东进南下。300hPa动能转换E的带状分布非常清楚,并且E的大值中心分布在高空急流(>50m/s)的两侧,这也表明高空急流在能量转换的过程中起到非常重要的作用。涡度、散度和位涡的分布特征与引发此次沙尘天气的河西小槽位置比较一致。轨迹分析表明,在300hPa高空主要是低压槽起引导作用,500hPa向东南方向移动,而在700hPa气块在高原北侧的绕流非常明显。将沙尘浓度和气块轨迹叠加在一起时,可以确定沙尘的输送路径,所以它有一定的预报实用性。更多还原

【Abstract】 A model simulation of "2002.3" sandstorm by nonhydrostatic mesoscale model MM5 is analyzed in an effort to study the mechanism of the sandstorm.The diagnosis of convective momentum transport (CMT) shows that, at every level,the maximum budget residual X of the horizontal momentum is located behind the trough,which X strengthened the northwest cold air flow to south.The angle between and was smaller than 90° behind the trough,that means accelerated northwest cold air flow to south and it is in favor of deepening the trough and moves to southeast. At the level of 300hPa, kinetic energy transfer E had clear belt distribution, and the maximum centers of E was mainly located on the each side of upper Jet, that showed the upper Jet played a very important role in kinetic energy transfer. The distribution character of vorticity and divergency is consistent with the trough that trigged the sandstorm.Model trajectories analyses indicated that there was airstream in the trough at the upper level of 300hPa, and it flow to southeast at the level of 500hPa, there exist mountain-plain circulation to the north of the Plateau. The sand transport routing can be determined by superimposing the sand concentration over the trajectories, theoretically, but the forecasting of the trajectories is difficult at now.更多还原