Mesoscale Characters Of Convection Process That Happened On Quasi-stationary Front In Western South China

In this paper, the conventional high-altitude and ground observations, Guangxi radiosonde station data, FY-2E satellite data, Guangxi Doppler radar data and data of92Guangxi automatic weather stations with six elements were used to analyze the mesoscale characters of five representative convection processes that developed on quasi-stationary front in western south China (Huanan). Large-scale environmental conditions of mesoscale convective systems (MCS) that developed on quasi-stationary front in the western of Huanan were summarized through studying circulation background, atmospheric stability and vapor condition of each process. And then automatic weather station data and Doppler radar data were used to analyze the surface mesoscale allobar, temperature field, streamline field and the propagation of convective cells. Finally, a basic conceptual model of MCS on quasi-stationary front in the western of Huanan development mechanism is presented in this paper. The main conclusions are as following:(1) The activities of weak cold air are the key factor to the generation of convection on front. Large scale environmental conditions of convection generation in summer in western Huanan often have, but front convection is infrequent because of lack of trigger convection. The intrusion of weak cold air make the quasi-stationary front moving southward and frontal uplift is the main trigger form of the front convection.(2) When weak cold air diffused from the north to the south, the quasi-stationary front moved into Guangxi from the northern Guangxi or quasi-stationary front fronttogenesis strengthen in Gaungxi with the intrusion of weak cold air. In the front of quasi-stationary front there was southerly air stream, and in the behind of quasi-stationary front there was northerly air stream.(3) The quasi-stationary frontal uplift was the trigger mechanism of MCS. Under the favorable weather scale environmental condition, weak cold air diffused to Guangxi and propelled quasi-stationary front moving southward. The front uplifted the warm and wet air that accumulated in the surface mesoscale allobar and triggered the deep convection, after then MCS formed.(4) The mesoscale katallobaric field generated or strengthened ahead of the formation of MCS about2-5hours. During the process that quasi-stationary front moving southward, mesoscale katallobaric field was formed in the front of quasi-stationary front, and mesoscale anallobaric field was formed in the behind of quasi-stationary front. Warm and wet air accumulated in the surface mesoscale katallobaric field. After2-5hours when the quasi-stationary front moved to the position of the original mesoscale katallobaric field, quasi-stationary front uplifted the warm and wet air in the mesoscale katallobaric field and triggered MCS.(5) The convective cells spread and developed along the front. MCS was triggered and developed on the front, meanwhile moved southward with the front. Some convective cells moved eastward or westward influenced by the other factor while moving southward, so the synthetic moving direction was southeastward or southwestward. In summation, the convective cells propagated and developed on the front.