“4.12”沙尘暴天气的数值模拟及诊断分析

利用MM5中尺度数值模式,以T106实况资料作为初值场和侧边界值,对甘肃省河西走廊2000年4月12日强沙尘暴的强风天气形势和地面风场进行了数值模拟,并利用模式输出结果对这次过程作了诊断分析。模拟和诊断分析结果表明：MM5中尺度模式能模拟出产生这次强沙尘暴的强风天气形势和上升运动;沙尘暴爆发前3h河西走廊出现西北大风,并有大风向这一地区的明显辐合;沙尘暴发生在地面处于于暖状态的地区;位涡的水平分布特征对沙尘暴的出现时间和落区有一定的指示意义。沙尘暴区上空螺旋度垂直分布为高层负值,低层正值。螺旋度正值的演变与沙尘暴的出现有一定的对应关系。

Numerical Simulation and Diagnosis Analysis of "4.12" Sand-Dust Storm

Using the MM5 mesoscale numerical model and the T106 analysed data, the strong wind weather type and surface wind field of the strong sand-dust storm in Gansu Corridor on April 12, 2000 were simulated. the diagnosis analyses have done by the output results of the model. It shows that the MM5 model can simulate the strong wind and ascending motion of strong sand-dust storm area, the north-west wind is appeared and the strong wind is converged distinctly at Gansu Corridor before 3 hours of the sand-dust storm outbreak. The horizontal distribution of potential vorticity has certainly indication for occurring time and area of the sand-dust storm. Strong sand-dust storm area lies below the dense strip of isometric potential vorticity at upper troposphere. The vertical distribution of helicity over the sand-dust storm area is the negative value in the upper levels and the positive value in the lower levels. There is certain corresponding relation between the evolution of the positive value of the helicity and the occurrence of sand-dust storm.