Meso-scale Analysis And Numerical Simulation Of The Squall Line In Eastern China

1、Based on automatic station observation, satellite cloud image data, Doppler radar and NCEP、JRA reanalysis data, the weather situation of a rare, wide range strong convection weather on June 5th,2009 in East China is analyzed in detail. Results showed that the weather was good and the surface was warming significantly by following a trough cold advection effect in eastern China at 08:005 June. The formation of the cold advection in upper level and lower level warm advection of unstable stratification produced by the northeast cold vortex trough southward swing, and the southern Shandong Peninsula cold trough southward moving. The low level convergence and "Heat island effect" highlights afternoon caused by the land sea temperature difference and the high-altitude cold air’s join at 14:00, was the mainly trigger mechanism which caused the occurrence and strengthen of the strong convective weather. Through the study of the strong convection weather process, draw the conclusion:According to the characteristics and conditions of the squall line occurred in the large-scale weather background, detailed grasp the characteristics of strong convective weather before, to make our short term weather forecast and prevention of disaster weather plays a leading role as necessary. Although it was in the back of trough at 500hPa at 08:005 June, but at 200hPa it was still the southwest airflow power control, this time of satellite images also showed a large clouds over the East China Sea and in the east. Showed that before the cold trough crossing at 200hPa, there will still be cold air in low altitude, this was a warning of occurrence of squall line system in the afternoon.2、In QG (quasi-geostrophic) theory, the system was mainly influenced by the vorticity advection in the top and by the thickness advection. The values of the vorticity advection varies with height (YAH) and Laplasse term of thickness advection (LTA) of the co equation were calculated. It was showed that the large value range of LTA was significantly higher than that of VAH, by the contrast of the two value in the high and low layer in East China regional distribution map, which explained that the contribution to the value of ω of LTA is larger than that of VAH. That came to a conclusion, the system of the squall line was mainly influenced by temperature advection in the high and low layer in East China, and which was different from the general situation of QG theory.3、Based on the "RKW" theory, and used WRF to simulate the squall line process, with the large scale background field and radar echo data contrast, no obvious error, showed that the simulation was basically credible. According to the simulation results, respectively at 12:30,14:00,15:30,17:00, profile with the squall line direction approximately vertical, and focus on the analysis of the internal structure of a squall line, could find that between the cold pool and low-level vertical wind shear strength was the main reason for the development and maintenance of a squall line system. That was generated in the squall line early, the ground had not formed the cold pool structure obviously, the intensity of cold pool was considerably less than the low-level vertical wind shear, was not conducive to the development of squall line. But local thermodynamic conditions conducive to the development of squall line, promoted and strengthened the whole of the strong convective system. With the formation of a large number of thunderstorm precipitation water droplets in the air, at the same time the squall line in the dry and cold air sinking hollow tail, accelerate the evaporation of water droplet and the release of the latent heat, the formation of negative potential temperature perturbation cold pool center, which maked the ground cold pool strength, and gradually achieve the same low-level vertical wind shear strength quite, development to matured stage of squall line system at this time, the most powerful. Due to the large number of precipitation is the further accumulation of cold air to ground, cold pool the strength increased further, gradually strong low-level vertical wind shear, the squall line system gradually decline, with the passage of time, gradually disappearing. By simulating the main ideas, development of squall line system and maintain the case and the theory of "RKW" agreement.