Abstract: 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.

Key words: sandstorm, diagnostic analysis, momentum transfer, convective instability