华南强降水实测雨滴谱特征在云微物理方案中的适用性研究

华南地区对流活动频繁，常发生致灾性强降水。当前数值模式对华南强降水的预报能力显著偏低。精确描述云降水微物理过程是提升预报水平的关键所在。云微物理参数化方案计算效率高，被广泛用于业务精细数值预报模式。但其采用伽马函数描述雨滴谱分布时，常假设谱形参数为常数，这与观测事实严重不符，导致在模拟华南强降水时有明显不适用性。针对上述问题，本研究拟开展双偏振雷达-视频探空仪-2DVD雨滴谱仪联合观测试验，获取华南强降水微物理特征资料。基于大量雨滴谱实测资料，得到本地代表性谱形参数与截距参数线性相关关系，建立适用双参云微物理方案的伽马雨滴谱函数三参数高精度快速求解方法，应用到以Thompson方案为例的双参方案中。基于试验资料，采用模式结果正演双偏振量和双偏振雷达反演雨滴谱相结合的方式，对比检验和评估新旧方案对华南强降水的模拟效果，提出科学合理优化方法，以解决云微物理方案在华南强降水模拟中的不适用性问题。

Convective activities are frequent in South China, and often lead to catastrophic heavy rainfall. The skills of quantitative precipitation forecast for heavy rainfall over southern China remain rather low for the global and regional operational numerical weather models. Accurate descriptions of cloud and precipitation microphysical processes are the keys to improving the forecast skills. Bulk microphysics parameterization schemes are widely used in operational high-resolution numerical prediction model systems due to their high computational efficiency. However, when describing the raindrop size distribution (RSD) with gamma function, they usually assume the shape parameters are constant. These are obviously inconsistent with the observed facts, resulting in significant inapplicability in simulating heavy rainfall in southern China. In order to solve the above problems, joint field experiment will be carried out with polarimetric weather radars, Hydrometeor Videosonde (HYVIS) and 2D-Video-Distrometers (2DVD) to obtain the microphysical characteristics of heavy rainfall system in South China. The representative linear correlation between shape parameters and intercept parameters will be obtained based on many RSD observations. Then, a high-precision and fast solution method of three-parameter for gamma function will be established for the double-moment bulk microphysics schemes. Take the Thompson scheme as an example, this method will be applied to the double-moment bulk microphysics schemes. New and old microphysical schemes will be used to simulate the heavy rainfall in South China, and the simulation results will be forwarded into polarimetric radar parameters. Based on the experimental observation data, the raindrop size distributions will be retrieved from the polarimetric radar observations. The simulation results of new and old schemes will be compared and evaluated. Finally, a scientific and reasonable optimization method will be proposed to solve the inapplicability of bulk microphysics schemes in simulation of heavy rainfall in South China.