1.Taiyuan Meteorological Bureau of Shanxi Province;2.China Meteorological Administration Training Center
2016年6月12—13日在同一冷涡背景下，山西境内连续两天出现强对流天气，12日为分散性对流，13日为大范围强风。基于多源资料通过对比探讨次天气尺度系统及其演变对风暴环境进而对风暴结构的影响，结果表明：1）6月12日对流孤立分散，回波强度小于55 dBZ；13日强对流由准线性风暴发展成尺度较大的弓形回波，中心回波强度55～60 dBZ； 2）12日500 hPa冷涡西侧低涡尚在发展初期，距离山西较远；13日形成次天气尺度切断低涡，低涡底部急流有气旋式切变，低层配合切变线和冷锋东移影响山西； 3）12日低层湿度小，0～3 km垂直风切变仅1.6×10-3 s-1，分散性对流由地面弱辐合线触发；13日切变前偏南水汽输送使低层高湿，叠加中层干冷空气形成不稳定层结，受低涡影响0～3 km风垂直切变增强至5.0×10-3 s-1，初始对流由低层变性冷锋触发，随后阵风锋组织风暴形成飑线，冷池与0～3 km风切变相互作用使飑线维持； 4）冷涡西侧次天气尺度切断低涡系统影响冷锋及低层切变线、湿度与层结稳定度、风垂直切变、冷池及阵风锋，是对流触发、组织及发展形成飑线和弓形回波的关键因素，是短时预报的关键系统。
On June 12-13, 2016, under the background of the same cold vortex circulation, strong convective weather occurred in Shanxi for two consecutive days. The 12th was a scattered convective weather, and the 13th was a large-scale strong wind. Based on multi-source data, the influence of sub-synoptic scale system and its evolution on the storm environment and storm structure is discussed through comparison. The results show that: (1) On June 12, the convective was isolated and dispersed, and the echo intensity was less than 55 dBZ. On the 13th, the strong convection developed from quasi-linear convective storm to larger-scale bow echo, with central echo intensity of 55~60 dBZ. (2) On the 12th, a low vorticity on the west side of the 500 hPa cold vortex began to develop far away from Shanxi. On the 13th, a sub-synoptic-scale cut-off vortex was formed. The jet at the bottom of the low vortex had cyclonic shear, and the low-level matched shear line and the cold front moved eastward to affect Shanxi. (3) On the 12th, the low-level humidity was low, and the vertical wind shear at 0-3 km was only 1.6×10-3 s-1, the scattered convection was triggered by the weak convergence line on the ground. On the 13, the southward water vapor transport before shear made the low layer high humid, superimposed the dry and cold air in the middle layer to form unstable stratification. Under the influence of low vortex, the vertical shear of the 0-3 km wind increased to 5.0 ×10-3 s-1. The initial convection was triggered by the low-level denatured cold front, and then the gust front organized the storm to form a squall line. The interaction between the cold pool and 0-3 km wind shear maintained the squall line. (4) The sub-synoptic-scale cut-off vortex system on the west side of the cold vortex affected the cold front and the low-level shear line, humidity and stratification stability, vertical wind shear, cold pool and gust front, which was the key factors for triggering, organizing and developing convection to form squall line and bow echoes, and were the key systems for short-term forecasting.