Preliminary Study Of Cloud Parameters Based On Ground-Based Remote Sensing

High temporal and spatial resolution of cloud micro structure and macro characteristics can be obtained with the use of millimeter wave cloud radar (MWCR).The formation, dissipation and evolution of cloud are closely related to the distribution and variation of temperature and humidity in the atmosphere. Microphysical parameters are needed in order to get a further study of the physical process, structure and radiation effect of cloud. Such microphysical parameters can be retrieved with the data from synergic observation of cloud by MWCR and microwave radiometer (MWR). This paper carries out a preliminary study of microphysical parameters retrieving based on certain observation and experiment. The main works and conclusions are as follows:1. Cloud observation data of Nanjing is enriched and expended with the acquisition of data during the preliminary experiment which combines ground-based MWCR and MWR. The summarize and classification of cloud according to the observed phenomenon and macro characteristics offers the base data sets for further study on the operational automatic observation and classification by MWCR.2. Try to retrieve the liquid water content (LWC) and effective radius (Re) of the cloud and discuss the results and applicability of several representative cloud types by different retrieving methods. The results show that only rely on single parameter retrieving method by MWCR, that is, empirical formulas like Z-LWC, Z-Re based on the radar reflectivity factor and LWC (or Re),can be applied only in some certain universal cases. In this way it is failed to tell the differences of microphysical parameters which caused by the differences of cloud drops’particle phase and cloud type. But such microphysical parameters retrieved by combing the radar reflectivity factor Z measured by MWCR and liquid water path LWP from MWR has considered the distribution of liquid water content and temperature profile in actual atmosphere, which can partly reflects these differences. The results of retrieved microphysical parameters combining MWCR and MWR to the warm stratus and stratocumulus cloud are fairly consistent with the droplet spectrum measured by aircraft or theory statistic, while the results of cold cloud even worse.3. The macro and micro characteristics in one process of stratocumulus and another process of stratus cloud before weak precipitation are analyzed in this paper. With the application of NCEP 1°×1° reanalysis data and upper air sounding data, the synoptic situation and physical quantity field which affect the formation, dissipation and evolution of cloud are diagnosed. In this way the influence of cloud microphysics process from variation of such physical quantities can be properly explained. It shows that synoptic-scale or meso-scale uplifting and water vapor flux convergence in proper levels provide dynamic and vapor conditions for growth of cloud.