Abstract: Black sandstorm has an important effect on the products of industry and agriculture and the people’s livelihood in Minqin County,Gansu Prouince,China, on April 24, 2010. More parameters associated to strong storms are studied, such as Instability Atmospheric Energy and thermal parameter V-3θ and dynamic parameter for StormRelative Horizontal Helicity (SREH), by using 24hour sounding observation data in Minqin between April 24 and April 25,2010. The results indicated that the positive instability energy still exist in atmospheric surface layer as black sandstorm starts blowing in Minqin, black sandstorm suddenly sprang up at surface boundary layer, cause sanddust particulates concentration increased in the areas of positive instability energy, then it formed a terrifying wall of black sandstorm. black sandstorm is a kind of the potential instability energy that caused by the air with upperlayer wet and lowerlayer dry. low humidity is not conducive to more precipitation in the low layer atmosphereare，and provides a better environmentin the vertical direction for the occurrence of sandstorm. The atmospheric stratification was convective instability state bellow 500 hPa before the sanddust storm, the vertical distribution characteristics of wind field is the clockwise rotation from bottom to top, which favours the development of Black Sandstorm. The influence of convective instability has been remarkably weakened after black sandstorm, the vertical distribution characteristics of wind field is the counterclockwise rotation in midlower troposphere, which are unfavorable for the development of vertical ascending motion. all this signs the wind toned down. A low value center of SREH exists in the middle part of of Hexi Corridor, the centers rate is -870 m2/s2 during Black Sandstorm, which is far lower than the critical value -600 m2/s2 for strong sandstorm. The good corresponding relationships among sandstorm intensities and the low value center of SREH. When Minqin’s SREH 0 in the upper hand, dust storm is over and visibility improved.

Key words: black sandstorm, stability, atmospheric stratification, helicity