Observation and Numerical Simulation Study of a Squall Line Process
Miao Ziqing;He Hongrang;Bai Shigang;Tang Pengyu;Institute of Meteorology and Oceanography, PLA University of Science and Technology;No.96219 Army of PLA;No.96319 Army of PLA;
A squall line process occurred on 31 March 2014 in Guangdong was analyzed by using the observed data and the numerical simulation model. The result shows that the squall line occurred in the environmental conditions of the strong low-level vertical wind shear and the upper level dry vapor. During the strong stage,the convective cells in squall line characterized by heavy precipitation supercell with a bound weak echo region(BWER) and an echo overhanging structure. The forefront of squall line had an obvious gust front and a weak echo channel in the back side, a weak echo channel was corresponded to the sloping rear inflow jet(RIJ)accompanying a long time maintenance, which played important roles in the formation of the "bow" echo, the maintenance and fast moving of the surface wind and the squall line. According to the analysis of high resolution data of the model output, it showed that the squall line moved into the residual cold pool lead to strength of the cold pool during the weakening stage. At this time, the squall line presented a secondary development due to the southwest warm wet current strengthening. The three-dimensional structure of mature squall line showed that there were two branches of inflow at the low level with two expenditure flow at the high-level. It was easy to form the suspension echo and weak echo region(WER). Divergence downdraft airflow in the lower level of rear inflow(below 600 hPa)was the reason of the formation of the ground wind. The "Vortex bunch" on both sides of convection also had great effects on the accelerated inflow of cold and warm air, the height and strength of the convection development and the long-term maintenance of convection.