Thirty - one cases of p recip itation p rocess in July to August of 2007 over Qilian mountains have been classified using the dominant air currents at the level of 500 hPa and cloud patterns of FY - 2D satellite images. The difference between the 500 hPa average geopotential height for grid point on 110°E (H1) and that on 90°E (H2) in the range of 30°N - 45°N was used as criterion of classification, and the p recip itation p rocesses have been classified as three main types, including southwest air current, northwest air current and flatwest air current type. Southwest air current type is also divided into moving and blocking two subtypes and northwest air current type into cold advection and Hetao cold vortex two subtypes. Using p recip itation data from automated weather stations in the experimental region, the circulation characters and p recip itation intensity for each synop tic type have been analyzed. It is found that the total p recip itation of the south slope ismore than that of the north slope about 44% in the same sea level elevation in summer 2006 over Qilian mountains, but for climatic state and the year of 2007, the total p recip itation of the north slope wasmore than that of the south slope, and the dominant southwestwind in 2006 but northwestwind in 2007 at the level of 500 hPa overQilian mountains.

Based on aerological observations at the hail supp ression experimental stations of Yongdeng andMinxian counties of Gansu Province during 1979 - 1987, as well as surface meteorological observations at the same time, the upperwinds under the six different weather conditions of strong hailstorm, weak hailstorm, thunderstorm, shower, overcast and sunshine were analyzed. Results show that significant defference p rezented in low airwind direction shear, middle airwind velocity shear and jet in upper air before haill falling under the strong hailstorm weather condition compared with those of otherweather conditions, which is useful to forecast hailstorm and study its formation mechanism.