A research on the interaction between baiu front and tropical cyclone and mesoscale organization of convection

建立了一个数值模式，可以很好地模拟这些现象中的白羽锋、热带气旋和中尺度有组织对流。为了改进中尺度对流分解模式（Yamasaki, 1986）中积云尺度的参数化，将积云尺度的云水作为一个预测变量。另一个改进是没有使用Arakawa和Schubert（1974）在云参数化中使用的非常小的云分数假设，因为这里处理了积云对流的中尺度组织。将该模型应用于与白球锋和热带气旋相关的云团，并与以往几种不同参数化方案的模型结果进行了比较。结果表明，新模式能较好地模拟白云锋与热带气旋中尺度结构之间的关系。对于白锋面与热带气旋的相互作用，分别在白锋面南面有热带气旋和没有热带气旋的情况下进行了数值实验。与白锋有关的雨量，亦因热带气旋的存在而增加。阐明了其增强过程和机理。采用非流体静力积云尺度解析模型进行了数值实验。通过改进冰相参数化，特别是云冰和霰的生成速率和过程，可以更好地模拟热带气旋眼壁。另一种可以有效地用于并行计算机的云模型被开发出来。该模型可以成功地模拟与热带气旋和龙卷风相关的超级单体。

A numerical model was developed that can well simulate Baiu fronts and tropical cyclones and mesoscale organized convection in these, phenomena. In order to improve cumulus-scale parameteriztion in the mesoscale-convection- resolving- model (Yamasaki, 1986), cumulus-scale cloud water was treated as a prognostic variable. Another improvement is that an assumption of a very small cloud fraction, which has been used in cloud parameterization of Arakawa and Schubert (1974), was not used because mesoscale organization of cumulus convection is treated. The model was applied to cloud clusters associated with baiu fronts and tropical cyclones and compared with results from several models with different parameterization schemes proposed in the past. It was found that a more realistic simulation could be made with a new model for cloud dusters associated with the baiu front and mesoscale structure of tropical cyclones.As for interaction of a baiu front with a tropical cyclone, numerical experiments were performed for two cases with and without a tropical cyclone to the south of the baiu front. The rainfall associated with the baiu front was found to be enhanced by the presence of a tropical cyclone. The process and mechanism for its enhancement were clarified.Numerical experiments were also made with the use of a non-hydrostatic cumulus-scale resolving model. By improving the ice phase parameterization, particularly generation rates and processes of the cloud ice and graupel, an eyewall of a tropical cyclone was better simulated. Another cloud model that can be efficiently used for a pararell computer, was developed. The model could simulate successfully a supercell associated with a tropical cyclone and a tornado in it.