南疆“3.12”强沙尘暴天气数值模拟与诊断分析

春季是南疆塔里木盆地沙尘暴天气的高发季节。利用GRAPES中尺度数值模式,以GFS资料作为初值场和侧边界值,对新疆2011年3月12日南疆出现的强沙尘暴天气进行数值模拟,并利用模式输出结果对这次过程作诊断分析。结果表明,GRAPES中尺度模式对高空槽、西风带、地面温度等强沙尘暴主要影响系统发生、发展及强度模拟效果较好,能模拟出产生这次强沙尘暴的强风天气形势和上升运动;西西伯利亚地面冷高压爆发性南下并强烈发展是造成强沙尘暴天气的重要地面天气系统;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;上升运动转为下沉运动是沙尘暴的最强时段。

Numerical Simulation and Diagnosis Analysis of “3.12” Sandstorm in South Xinjiang

The frequency of sandstorm events is the highest in spring in Tarim Basin,China.A strong sandstorm happened in south Xinjiang on March 12,2011 was simulated by making use of the GRAPES mesoscale numerical model and the GFS data.Then a diagnosis analysis was done based on the output results of the model.It was proved that the GRAPES model can well simulate the occurrence,development and intensity of main weather systems including upper trough,westerly belt and surface temperature.They are main influence factors of the strong sandstorm.It can also well simulate the strong wind and ascending motion of strong sandstorm.The south invading and violent development of the cold West Siberian High is just the reason to cause strong sandstorm in the Tarim Basin.The horizontal distribution of potential vorticity has a certain indication for occurring time and area of the sandstorm.The helicity over the sandstorm area is negative value in the upper levels and positive value in the lower levels.There is a certain corresponding relation between the occurrence of sandstorm and the evolution of the positive value of the helicity over the sandstorm area.The time when ascending motion turned to declining motion was just the time of the strongest sandstorm happened.