Comparative Analysis Of Different Types Of Severe Convective Weather Affected By Cold Vortex

The multi-cell storm in northeast of Huabei region and squall line in Huanghuai region occurred under the same circulation background of northeast cold vortex on 22 August 2015.Based on the meteorological observation data,this paper first analyzes the characteristics of meso-scale convective systems and environmental conditions in different types of severe convective weather.Based on the results of WRF meso-scale numerical model simulation,the differences between shape structure evolution and movement process is compared.This reasons for structural evolution differences and effect of cold vortex are analyzed in addition.The research shows that:(1)In same cold vortex,Northeast of Huabei located in southwest quadrant of cold vortex and in front of ground cold high pressure.Dispersive multi-cell storm is located in vortex cloud at the periphery of cold vortex lead to strong convective weather dominated by short-term heavy rainfall.Huanghuai region is located in rear of cold trough and cold vortex and in front of cold front on ground.Multiple convective cells form in clear sky behind trough,forming a herringbone system which leads to rainfall,thunderstorms wind and hail.(2)Although different strong convective weather develop along the same north-south low-altitude shear line,differences in thermal and water vapor conditions lead to different environments.Northeast of Huabei region is affected by the warm ridges,so there is no obvious cold advection at high level,and the low-level easterly air flow brings water vapor transport that causes precipitation to form along the near-surface convergence line in wet environment field.Dry cold added air at high-level in north of Shandong and low-level warm ridges formed vertical thermal instability,the lack of low-level water vapor makes wind and hail in Huanghuai region occur in relatively dry environments.(3)The shape evolution of two meso-scale convective systems is different.North convection was combined by surface winds and uplift of terrain to form a multi-cell storm with a northwest-southeast alignment.It travels slowly south-southeast by downwind propagation and bring rainstorm.The southern linear convection was formed by combination of several isolated cells formed in northwest of Shandong and north of Henan.(4)The intensity of mid-level inflow have significantly different effects on the organization of two convective systems.The increase of rear inflow of squall line at middle layer mainly comes from increase of westerly component,which is related to enhancement of environmental wind field caused by evolution of cold vortex.The mid-layer wind field where north convection is located is weak and the whole layer is wet,which is not conducive to the development of multiple cell storm organizations.The middle troposphere of south squall line is located in westerly guiding airflow which is stronger than north convection.The inflow is strong and ambient air is dry,which is favorable for the formation of strong descending airflow.Enhanced inflow enhances the vertical wind shear in the middle and lower layers through momentum transfer,thereby promoting the development of thunderstorm high pressure and cold pools.This is conducive to the propagation of convective cells,and the development of organizations to form continuous linear convection.