河西走廊东部一次强沙尘暴天气过程的动力特征诊断分析

Diagnostic Analysis of Dynamic Characteristics of a Strong Sandstorm Weather Process in Eastern Hexi Corridor

摘要: 利用地面气象观测站逐时风向风速、海平面气压、加密自动站观测数据等，对2018年4月4日河西走廊东部极端大风沙尘暴天气的影响系统及动力条件等方面进行了分析。结果表明：乌拉尔山阻塞高压快速发展北抬，脊前冷涡异常南压，引导极地冷空气爆发性南下，冷锋后大风及太阳辐射日变化是造成河西走廊东部强沙尘暴的主要原因。沙尘暴前期，大气干热，当冷空气侵入，冷暖空气剧烈交换，近地层出现不稳定层结，产生热力对流；深厚的辐合辐散区与高空槽、地面冷锋的配合有利于上升运动，使沙尘扬起。随着高空急流的进入，动力抽吸加强，低槽前暖空气上升，槽后冷空气下沉，加剧大气斜压不稳定，出现位能向动能转换；高层动量、动能向下传递，最终造成地面风场加大，沙尘暴天气爆发。

Abstract: Based on hourly wind direction and speed, sea level pressure and automatic observation data from ground meteorological stations, the influence system and dynamic conditions of extreme gale and sandstorm weather in the eastern Hexi Corridor on April 4, 2018 were analyzed. The results show that the strong sandstorm in the eastern Hexi Corridor is mainly caused by the rapid development of Ural blocking high and the abnormal southward pressure of cold vortex in front of the ridge, which leads the explosive southward movement of cold air in the polar region. In the early stage of sandstorm, the atmosphere is dry and hot. When the cold air invades, the cold and warm air exchanges violently, and unstable stratification occurs near the stratum, resulting in thermal convection. The cooperation of the deep convergence and divergence area with the upper trough and the surface cold front is conducive to the upward movement and the dust is raised up. With the entry of upper-level jet stream, dynamic suction is strengthened, warm air rises in front of the low trough, and cold air sinks behind the trough, which worsens atmospheric baroclinicity instability and leads to potential energy conversion to kinetic energy. The momentum and kinetic energy of the high level are transferred downward, and eventually the surface wind field increases and sandstorm weather breaks out.