【摘要】 利用常规气象观测资料和ECMWF数值预报产品初始场资料,对2018年3月19日河西走廊东部的大风强沙尘暴天气过程进行了分析。结果表明:500 hPa蒙古西部到新疆东部低槽是此次区域性大风沙尘暴发生的影响系统,700 hPa河西走廊东部变形场是大风沙尘暴的触发系统,午后气温日变化加大了地面冷锋前后的气压梯度和温度梯度,冷锋前后Δp3达8.3h Pa,造成冷锋移至河西走廊东部产生强烈锋生是沙尘暴爆发的直接原因;随着河西走廊东部上空高空西风急流风速增大、高度降低,风速为14 m·s^-1的强风速带伸展到地面,将高空动量向下传播,加之北风前锋到达之处,沙尘暴爆发;沙尘区低层辐合、高层辐散,以及无辐散层和-52.6×10^-3hPa·s^-1的强上升运动一致,有利于增大近地面沙尘浓度;V-3θ曲线显示强垂直风速切变和上干下湿的状态,为此次沙尘暴的发生发展提供了不稳定的环境条件;前期降水稀少,气温异常偏高的气候背景和边界层逆温层破坏,中低层干热及地面风速增大,为沙尘暴天气爆发提供了前期气候背景和不稳定及动力条件。更多还原

【Abstract】 Based on conventional observation data and ECMWF numerical forecast products,the causes of strong sandstorm was analyzed in the east of Hexi corridor on 19 March 2018.The results showed that:The lower groove trough in 500 hPa was influence system of this sandstorm. The 700 hPa deformation field in the east of Hexi corridor provides triggering system for development of sandstorm.The large gradients of pressure and temperature before and after cold front were caused by the variation of temperature in the afternoon,and the Δp3 reached 8.3 hPa,the dust storm was a process of strong frontogenesis when the cold front moved to the east Gansu corridor. With the wind speed of the high-altitude westerly jet increases and the height decreases over the east of Hexi Corridor,the strong wind speed of 14 m·s^-1 extends to the ground,and the high-altitude momentum is propagated downward,the dust storm erupts where the northerly forward arrives. Low level convergence and highaltitude divergence provides environmental conditions for the formation and development of this strong sandstorm. The V-3θ curve shows that the distribution characteristics of up wet and down dry and up cold and down warm provide potentially unstable environmental conditions for the occurrence and development of this strong sandstorm. Precipitation is scarce and the temperature is unusually high,providing a pre-climatic background for this strong sandstorm. Before the sandstorm broke out,the mean wind speed was very slow and the temperature was comparatively high and the humidity was comparatively low,and strong inversion layers existed in the upper atmospheric boundary layer（ABL）,while after the sandstorm broke out,the wind speed increased sharply and the temperature decreased and the humidity increasd sharply,consequently the inversion layer was rapidly destroied.更多还原