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

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.