初生阶段西南涡发展与消亡的物理机制

采用涡旋运动稳定性方法，结合大尺度环境场和积云对流潜热释放，研究初生西南涡发展与消亡的物理机制。结果表明:（1）在稳定层结和不稳定层结条件下，当大气扰动频率超过对应的临界频率时，初生西南涡均可以维持并向成熟涡转变；当大气扰动频率未超过临界频率时，初生西南涡要么因频散而消亡，要么在维持一段时间的纯涡结构后消亡，不能发展为成熟西南涡。（2）初生阶段，大尺度场的辐合辐散是西南涡发展和消亡的主要因素，辐合才有可能使得初生西南涡发展，辐散只能导致初生西南涡消亡；小尺度的潜热加热则决定着稳定层结下的扰动临界频率，进而影响稳定层结下初生西南涡的发展及向成熟西南涡的转变。 

Physical Mechanism of the Development and Extinction of Primary Southwest Vortex

With the vortex motion stability method, combined the large-scale environmental field and the convective latent heat release of cumulus cloud, the physical mechanism of the development and extinction of the primary southwest vortex are studied. The results show that: (1) In the stable stratification and unstable stratification, when the atmospheric disturbance frequency exceeds the corresponding critical frequency, the primary southwest vortex can maintain and transform to the mature vortex. When the atmospheric disturbance frequency does not exceed the critical frequency, the primary southwest vortex is either perished by dispersion or perished after maintaining a pure vortex structure for a period of time, which cannot develop into a mature southwest vortex. (2) In the primary stage, the convergence and divergence of the large-scale field is the main factor for the development and extinction of the southwest vortex, and only the convergence can make the primary southwest vortex develop, while the divergence can only lead to the extinction. The small-scale latent heat heating determines the perturbation critical frequency under the stable stratification, and affects the development of the primary southwest vortex and the transition to the mature southwest vortex under the stable stratum.