The PMS p robeswere used to measure microphysical parameters of a summer stratus on August 15, 2007 inMinle of Gansu Provinc. The cloud structure including particle’s vertical distribution, liquid water content and particle spectrum type was analyzed.Results show that: (1) the cloud structure of the stratus is clear, and there is an inversion layer in this cloud; (2) the average of liquid water content is 0. 012 g·m- 3 in the cloud, and mainly concentrated in the layers of 4 100 - 4 200 m and 4 700 - 5 000 m; (3)this cloud accordswith the Bergeron’s catalytic cloud and water cloud interaction model, so we can seed crystals to achieve the objective of increasing p recip itation.

Based on the three - year air observational data, the impact ofweather conditions on aircraft icingwas analyzed, and the general rules of aircraft icing was summed up to enhance flight safety and security. The results show that the aircraft icing frequently occurred in winter and sp ring, and mostly in the areaswith p lenty ofwater vapor; the aircraft icing usually formed in the cloud with the temperature range of 0 to - 11 ℃, and especialy in the range of - 1 to - 8 ℃;when there wasmore supercooled water in the cloud,the aircraft icing would be more intensive.

Based on the data measured by PMS and GPS during a cold front process on April 24,2002, the horizontal and vertical distributions and spectrum characteristics of microphysical quantities of cloud drop and ice crystal were analyzed in this paper. And the optimum parameters of simulated functions were given out, the possible microphysical mechanism which involved were discussed. On these facts, the potential ability of enhancement rainfall was discussed and estimated.

By using the lightning data in 2000 and 2002 around Lanzhou，lightning characteristics such as daily variation，spatial density，intensity and polarity of lightning are analyzed and also compared with those in Shandong province.The results indicate that major cloud-to-ground（CG）flashes of lightning are negative.The mean intensity of positive flashes is stronger than that of negative flashes and their ratio is over average during 12：00 to 00：00.Daily variety of the CGand negative flashes is bimodalundulance，other than positive flashes unimodal.The biggest flashes frequency center locates in Weiyuan and Longxi county，and accord with the location of hail source are aand hail affecting zone. Furthermore，the spatial distribution of lightning is closely related to the topography and under lying surface and synoptic climatic background

Using the data of 116 times’samples of aircraft artificial precipitation enhancement operation from 2000to2003（March to October），and based on the real time data at 500 hPa at 08：00，five weather types which benefit aircraft artificial precipitation enhancement were obtained according to different path of the cold current in vaing Gansu province：plateau low trough，southwest aircurrent，straight fluctuant，northwest air current and northern low trough.