Abstract: A strong wind blowed the train down and made great casualties in Xinjiang on February 28, 2007. The cause of this strong wind is analyzed based on the conventional meteorological data, anemometers along the railway and WRF model. The results show that the strong pressure gradient between Junggar Basin and Turpan Basin provided favorable dynamic conditions for the development of the strong wind. It was a downslope windstorm, the origin of this windstorm couldn’t be attributed to either the effect of narrow or the downward- tansporting of upper momentum, two factors might have made it such a damaging storm. 1) Vertically propagating gravity wave returns to the surface with strong wind after it is reflected many times by critical level and/or inversion layer. 2) The strong pressure gradient enables gap flow to be forced through valley more quickly in the range, accelerates the surface wind when the airflow drops sharply along the steep terrain.

Key words: strong wind, downslope wind, gravity wave, critical level, inversion layer

摘要： 利用常规气象资料、 铁路沿线测风站资料以及中尺度数值模式WRF, 对2007年2月28日造成新疆列车颠覆及重大人员伤亡的强风天气进行分析。结果表明, 由于天山山脉的阻挡, 入侵新疆的冷空气在准噶尔盆地内大量堆积, 从而使峡谷两端的准噶尔盆地和吐鲁番盆地之间产生了很强的气压梯度, 为此次强风天气的发展提供了有力的动力条件。这是一次强下坡风暴, 其起因与地形的狭管效应无关, 也不是高空动量下传的结果。造成这次强风天气的原因可能有两个: 1) 被迫抬升的空气质点在重力的作用下产生垂直振荡, 形成重力波。 垂直传播的重力波在遇到临界层和逆温层后, 经过多次反射, 返回地面时形成强风; 2) 强的气压梯度迫使气流加速穿越峡谷, 加速后的气流沿陡峭的地势下降时使风速进一步加大。

关键词: 强风, 下坡风, 重力波, 临界层, 逆温层