Squall Line Characteristics and Formation Conditions in Liaoning Province
According to the squall line recognition standards,36 squall line processes are identified based on the radar composite reflectivity mosaic product in Liaoning Province from May to September 2015-2020.The spatio-temporal distribution of squall line characteristics and several different formation environment characteristics are summarized.The results show that the areas with the maximum frequency of squall line formation in Liaoning Province are from northwestern Liaoning and Chifeng City to Aohan Banner,fol-lowed by the west of Bohai Sea to the sea surface of Bohai Strait.The areas with the lowest frequency of squall line formation are the mountain line of Tangshan and Qinhuangdao in the east of Hebei Province.The vast majorities of squall line processes occur in June to August,while the least squall line processes occur in May.Squall lines are mainly formed from 12:00 BT to 21:00 BT,in which the period from 14:00 BT to 17:00 BT is the concentration period of squall lines.The coverage of squall line varies from 1 14 km to 273 km,with maximum reflectivity 65 dBz,average life cycle 3.2 hours and the average moving speed 59.4 km·h-1(16.5 m·s-1).33.3％of squall line processes in Liaoning Province are of the fault line type,19.4％are of the rear extension type,36.1％are of the fragment type,and 11.1％are the strati-form cloud embedding type.The main organizational form is stratiform cloud trailing type(TS),while the parallel stratiform cloud type(PS)and stratiform cloud leading type(LS)occurrless.55.6％of squall lines dissipate in the form of reverse broken lines,8.3％dissipate in the form of contraction lines,and 36.1％dissipate in the form of reverse fault zone.In terms of the circulation situation of squall line forma-tion in Liaoning,the cold vortex front type is the most common,followed by the low trough front type.The special circulation situation of squall line formation in Liaoning is the cold vortex rear type,accounting for 16.7％.The convective available potential energy and the sink convective available potential energy of each circulation pattern show the characteristics of"double 1000".Different circulation patterns have dif-ferent characteristics in water vapor supply,stratification instability,vertical wind shear and other physi-cal quantities.
万方数据
维普
