为了研究夏季沙尘暴的发生发展规律、提高沙尘暴的预警准确率,利用常规气象观测资料、NCEP/NCAR 1°×1°再分析资料和FY2C云图资料,对2013年7月30日河西走廊盛夏季节的大风沙尘暴天气过程成因进行分析。结果表明:(1)冷空气以阶梯槽形势分裂南下,为大风沙尘暴发展提供了对流不稳定的环境场条件;(2)近地面层强大气斜压性、地面鞍型场结构和气温日变化促使地面冷锋进入河西走廊后锋生,是造成这次沙尘暴的直接原因;(3)河西走廊中东部近地面的辐合上升气流与高空急流入口处右侧辐散抽吸作用叠加,触发了大风沙尘暴的爆发;(4)温度平流上冷下暖的垂直分布为沙尘暴的爆发提供了热力不稳定条件,存在对流有效位能大值中心,有利于沙尘粒子扬起,增大沙尘暴的强度;(5)沙尘暴出现时西风急流风速增大、高度降低,由急流中心向地面伸展的最大风速带将高空动量向下传播,北风前锋到达之处,沙尘暴爆发。另外,与春季特强沙尘暴天气相比,夏季沙尘暴的形成需要更大的启动风速、上升运动和热力不稳定条件。

In order to analyze the rule of the occurrence and development of summer sandstorm, increase the accuracy rate of sandstorm warning, the causes of the strong wind and sandstorm processes in summer on July 30, 2013 in Hexi Corridor was analysed by using the conventional meteorological observation data, NCEP/NCAR 1×1 reanalysis data and FY2C satellite data. The results show that: (1)The cool air's splitting to the South trough ladder situation provided convective instability environment for the development of sandstorm. (2)The strong atmospheric baroclinicity near surface, the saddle field structure and the day variation of air temperature urged the frontogenesis of the ground cold front after it invaded the Hexi Corridor, which was the direct cause of the sandstorm. (3)The superimposition of convergence updraft near the ground and the strong vertical circulation produced by pumping action of divergent flow on the right side of the upper-level jet's entrance region in the middle east section of Hexi Corridor, triggered the outbreak of the sandstorm. (4)The vertical distribution of temperature advection of up cold and down warm provided thermal instability condition for the outbreak of the sandstorm. The high value center of convective available potential energy was conducive to the raise of dust particles and the increase of the sandstorm's intensity. (5)The westerly jet wind speed increased, the height reduced when the sandstorm appeared, The maximum wind speed which was stretched from the jet stream center to the ground downward transmitted the upper momentum. Where the north wind forward arrived, the sandstorm outbroke. Compared with the strong sandstorm weather in spring, the formation of summer sandstorm need stronger starting wind speed, ascending motion and thermal instability.