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.