Studies On The Application Technology Of Artificial Precipitation Effort Evaluation And Case Studies

Effect evaluation is focused on whether the cloud and precipitation produces the expected significant changes after artificial seeding. The changes include macro and micro, so it is necessary to learn something about cloud microphysical characteristics. Based on the weather situation, the ground precipitation data, satellite imagery, radar data, as well as airborne particle measurement system (PMS) and other observational data, the cloud microphysical characteristics and the rainfall are studied in this paper.In the case of 418, First of all, an increasing number of large particles are found while the number of small particles is reduced. Secondly, the operation alters the structure of the cloud particle spectra which is multi-peak distribution in unseeded stage. However, it becomes stable after the cloud seeding. At the same time, the concentration of cloud droplets reduces while the particle concentration and precipitation particles increase significantly. The content of super cooled water is rich and increases with height when the temperature is -8 ~ -3℃at the operation height, while the number of ice particles goes to the other way. After the operation it produces more ice crystals which grow into precipitation particles with the support of super cooled water, resulting in an increasing of rainfall on the ground.Generally speaking, the formation of stratiform cloud relates to large scale air movements or irregular disturbances. The cloud detected in the 501case is in the mature stage of the precipitation cloud system and the direction of the cloud band is in southwest toward the northeast. Cloud top height is 5000m or so before the operation stage. The whole process of liquid water content value is relatively low with an average value of 0.005g/m3, so the available rainfall of the cloud is small. After 15minutes or so of the operation, however, LWC reaches to a peak, and goes up to 0.0937g/m3. At the same time, the LWC at 5400m and 6000m also reaches to the maximum value, respectively 0.0121, 0.1406g/m3. It indicates that operation has impacted the upward air movement and the development of cloud in the vertical direction. Trends of particle concentration and liquid water content in different height are relatively consistent. The particle concentration in 4800m reaches to 1600/L during the maximum LWC stage and particle average diameter is about 30 microns, simultaneously, in 5400m the concentration of particle closes to 1500/L with a average particle diameter of less than 10 microns, however, particle concentration exceeds 1600/L in 6000m and average particle diameter is about 5.2 microns. Large cloud particle concentration in the 4800m is relatively high and reduces after the operation. The high value of precipitation particle concentration is found, but it is reduced in the whole. The rainfall of compared zone and affected zone are all reduced, but the area of the rainfall region expands.