Yan'an Stratiform Cloud Microphysical Characteristics And Precipitation Mechanism

There is lack in fresh water in our country and it is an enhancing contradiction that population is going up, economy developing but a shortage of fresh water, which has a serious effect on the economy in some regions and social persistent development healthily in our country. Artificial precipitation-enhancement is an efficient approach to develop and make use of cloud water resource in the air, lighten water resource's shortage. The observation of cloud microphysical structure and the analysis of seeding physical effect play an important role in artificial precipitation-enhancement. In this paper aircraft has made vertical and synthetic detecting flying purposefully on 9.17,2003 according to cloud's macro and microstructure. Vertical layers and representative places of stratiform cloud on 9.17,2003 are analyzed using the observational data of Particle Measurement System (PMS), combined with satellite data, radar data, and precipitation data on ground. By this we have got cloud's microphysical structure and physical process of the natural precipitation, and the physical effect evidence has been testified according to observational data after LCO2 seeding.In the paper using the cloud particle characteristics and particle spectrum data in different heights, the vertical macro and microstructure or the coagulation water phase can be partitioned into 5 growth layers. There is an active growth layer and super cooled water exists with ice crystals that may be an important feature layer to occur rain in stratiform cloud. There is a vaporizing layer below 0 layer and it is far thick, which may be one of the important reasons of small precipitation on ground; In the paper the cloud and the rain drop size distribution in warm layer of stratiform cloud are calculated and analyzed. It is found that N (D) = N0Dnexp(- A D)can express the size distributions of little cloud drops , big cloud drops and rain drops. The observational and calculated results are well matched. The calculated mean diameter, mean square-root diameter, mean cube -root diameter and liquid water content are all well matched with the observational results; In the paper two examples have been analyzed by using the seeding region data and the possible affecting region data inleeward region. It is found that F-100, 2dc, and 2dp's particle concentrations increase in leeward region, but rising extent is different, which is likely to be due to difference of seeding effect time. In addition, by analyzing radar data and precipitation data on ground, we draw conclusion that the choice of seeding region condition is reasonable and the seeding has worked.