Study On The One Dimension Rain Category Model And The Practicality Observation

With the population explosion and the development of economy, the shortage of fresh water in current China has become a serious problem which greatly hinders the sustained and stable development in both regional and national economy. With respect to the artificial precipitation-enhancement, which is an effective way to alleviate the shortage of the water resource by exploring and utilizing the cloud water resource in the air, the most difficult problem lies in the inability to effectively evaluate the rainfall results. In this thesis, attempts have been made to improve the one-dimensional stratiform cloud raindrop category model and combine the model with radar echoes so as to make the raindrop spectrum stable and close to the spectrum actually observed. Undoubtedly, the improved model which can greatly enhance the precision of precipitation simulation has profound significance for the test for artificial rainfall effect and cloud precipitation accurate forecasting.Due to the weak updraft in the typical stratiform cloud in North China, it is impossible to measure the velocity and distribution of the air updraft by employing the existing means. And for the same reason, the velocity and distribution of the air updraft has always remained an uncertain factor in the preceding numerical study of cloud precipitation. Anyhow, the velocity and distribution of updraft has a relatively great impact on the intensity of precipitation and distribution of radar echo intensity profile line.In this thesis, by reprogramming the scheme of transformation between categories and the different schemes, improvement has been made to the one-dimensional stratiform cloud raindrop category model established by Institute of Atmospheric Physics of Chinese Academy of Sciences so as to make the raindrop size spectra and calculation more stable. In order to solve the impossibility to directlymeasure the stratiform cloud updraft, we simulate one cyclonic stratiform cloud precipitation on June 21, 2005 in Changchun, Jilin Province, by adopting various schemes of updraft and taking advantage of the relative accuracy of the raindrop category model in describing the natural evolution of the particle size distribution. Comparison has been made between groups of data calculated and the dBz profile obtained from the actual ground radar observation. At the same time, based on observation and the improved model combined with different schemes of updraft velocity, the raindrop spectrum, precipitation intensity and dBz profile are analyzed for the cyclonic stratiform cloud precipitation. Moreover, the group of data closest to those of the actual radar observation is further compared with the raindrop size distribution and the raingauge. Results show that, the improved model performs pretty well in analyzing the widening process of the raindrop spectrum of several kinds of updraft. Besides, the simulating result matches well with the actual raindrop spectrum observed as well as the surface rainfall intensity, and therefore helps to better achieve the aim of measuring the quantitative precipitation via comparison of the radar echo with the model.