The Research Of Physical Approaches For Effectiveness Evaluation Of Artificial Precipitation Enhancement And Case Studies

In this paper, the physical approaches for effectiveness evaluation of artificial precipitation enhancement are reviewed and summarized, in succession, two cases are detailed analyzed to demonstrate a scientific method of physically evaluating the effectiveness of artificial precipitation enhancement and discuss the design of aircraft observation for effectiveness evaluation.With synoptic charts, gauge data, satellite images, radar data, PMS data and other data of field observation, the two experiments of precipitation enhancement, the first of which is conducted in Henan Province on March 21, 2005 and the second is performed in Heibei Province on September 28, 2007, are analyzed, especially on the changes of macro physical and microphysical characteristics between seeded and unseeded, and the designs of aircraft observation of two cases are discussed.In the first case, it is revealed by the PMS data of an aircraft cloud seeding in stratiform cloud that, there are significant differences of macro and microphysical characteristics between seeded and unseeded clouds. The results indicate that the maximum concentration of small cloud particles is 1.36*108m-3 at the height of 4200m before seeding, and the corresponding mean diameter is about 5μm. The concentration and liquid water content of small cloud particles decrease after seeding, and their change below the seeding layer is more obvious than the one at the seeding layer. The mean diameter of small cloud particles increases from 17.32μm to 18.07μm at 5000m. The change of microphysical quantity after seeding is caused by cloud seeding. There are similar cloud particle spectrums at different heights.The method for Physical test of Henan Province case is efficient for detection and seeding of clouds. But orientation of horizontal flying at the height of 5000m and 4200m and vertical flying between 4200m and 5000m need to be adjusted. The method of seeding and detection of zonal stratiform cloud could be improved. The orientation of flying and banded cloud movement is sameness. The orientation of horizontal flying and vertical flying are adjusted by variation of wind.In the second case, analyzing radar echo, we find that operation is unsuccessful after seeding in the line passing Neiqiu, Shahe, Ningjin, and Xingtai. The same as the flight line from Longyao to Renxian. Further analysis and discussion are needed. As flying over Zhanhuang, it is indicated that, small cloud particles number concentration decreases, mean diameter and spectrum width increases. Big cloud particles and precipitation particles number concentration increases clearly.As the cloud system which mainly consists of stratifrom cloud has convection and moves quickly, Hebei case exist designing defects on flight program of flight line passing Neiqiu, Shahe, Ningjin and Xingtai. Horizontal and circular flying and vertical flying in Shijiazhuang and seeding in vertical flying have feasibility. Cloud is detected fully by horizontal and circular flying.