Characteristics of Mesoscale and Microscale Systems During a Severe Squall Line Process
By using the conventional observation data, disastrous loss data, AWS data, satellite infrared images, radar echoes and wind profiler products, a strong squall line process on 10 April 2012 was analyzed with statistical analysis and feature extraction method. The results show that: (1) The squall line is tightly belt shaped and composed of several tilt and deep convective cells. (2) The characteristics of mesoscal convective system (MCS) structure can be seen in FY2E infrared images. The sharp surface temperature front begins to form with MCS moving to east and precipitation cooling, moisture and heat transported by the southwest airflow and surface temperature rising. (3) Several parallel comb shaped short ribbon echoes appear and convection cells are continuously generated in the south side of the MCS. Finally they develop into a squall line echo belt in the earlier stage of the squall line system. (4) Local supercell hail storms with the structure of “front extend”, TBSS and false echo are generated continuously ahead of the squall line, causing most of the damages during this hail process. (5) The evolution of southwest jet stream including the gale area can be seen clearly in 5 min intervals wind profiler data in the early stage. (6) When the squall line system approaches, strong ascending motion ahead of the squall line can extend to 6000 m height influenced by the squall line mesoscale circulation, but the vertical velocity, Cn2 and SNR values are low. With the squall line passing, the horizontal wind shear is strong. Due to the dragging down action of strong rainfall, vertical velocity, Cn2 and SNR are significantly increased. After the squall line passes, all signals return to the initial phase.