“2.28”云南罕见春季强对流雷达回波特征分析与数值模拟

Characteristic Analysis on Radar Echo and Numerical Simulation of Spring Severe Convection in Yunnan on 28 February 2008

利用常规观测、红外云图、水汽图像、CINRAD-CC多普勒天气雷达观测、NCEP 1°×1°再分析资料和WRF模式,对2008年漏报的＂2.28＂云南罕见春季强对流中冰雹、雷打雪雷达回波特征进行分析和数值模拟研究。结果表明,此次过程是由强西南低空急流和地面冷空气引起,过程中昆明雷打雪上空为向高层扩展增强的逆风区,近地层零速度线呈＂S＂型暖平流形式,有钩状、块絮混合条状或片状回波对应,45 dBz的钩状回波强中心带在5-7 km处并向高层偏东方向伸展;玉溪强冰雹由＂弓＂型回波前部中-γ尺度中气旋活动所致,回波强度、零速度线自南向北呈汇合型和发散型的典型超级单体回波特征,60 dBz最强中心在5 km高度,雹云中〉50 dBz回波经历柱状、倒＂V＂和钩状,并与有界弱回波BWER相伴。WRF较好地模拟了整个强对流过程中的回波强度、形态和移动方向,验证了实况中冰雹、雷打雪云中存在强倾斜上升气流和冰雹云中倾斜上升气流,以及垂直上升运动大于雷打雪云中的事实。

Using the conventional observation data,NCEP 1°×1° reanalysis data,infrared cloud and water vapor images,CINRAD-CC Dopplar weather radar data,mesoscale numerical model WRF,the radar echo characteristic of hail and thundersnow occurred in Yunnan Province on 28 February 2008 are analyzed and simulated.The result shows that the severe convection process is caused strong low-level southwest jet and cold air.In this extremely convection process,the anti-wind area expanded and strengthened to upper level over the thundersnow in Kunming,the zero isotherm in low-level appears ＇S＇ warm advection pattern,there are corresponding to the mixed stripe shape echo with lump and floccus echo,45 dBz strong center of hook echo at 5～7 km heights extend to eastward direction of upper level.The severe hail in Yuxi are caused by head part of meso-%γ% scale cyclone in ＇bow＇ echo.During the period of hail,the zero isotherm from north to south in low-level appears the characteristic of typical supercell echo of convergence and divergence,the strong echo center of 60 dBz is at 5 km heights,the echo more than 50 dBz in the hailcloud went through pole,inverse ＇V＇ and hook shape echoes,which accompanies with BWER.The WRF（Weather Research Forecast） model well simulated the intensity,shape and moving direction of echo in the whole severe convection process.The fact that the hail and thundersnow-cloud have strong slantwise upward airflow,and the slantwise upward airflow and vertical velocity in the hail cloud is more than that of thundersnow,which can be well validated.