Analysis on an Exceptionally Strong Wind Gust Event in Beijing

An exceptionally strong wind gust process withmaximum wind speed over 32 m·s-1 appearing in Beijing on June 24,2006 is analysed.The Doppler weather radar data show that the strong wind gust is caused by a bow echo which is a part of a squall-line.The bow echo comes into being correlates with the rear influx jet which leads to the acceleration of southern part of squell-lineand then the squall-line combines with the new-generation cells in front of it.The deep meso-cyclone,the convergence at the low level and the divergence at the upper level play animportant role in the developmentof the strong cell making up of the bow echo.Based on the observation of Doppler weather radar,it could be deduced that the strong surface wind is caused directly by the downburst inside.The microwave radiometerand profiler data are used in the analysis of the environmental condition about the instability and the vertical wind shear in the lower troposphere.The greatCAPE,moderate vertical wind shear and the perpendicular wind distribution are favorite to the development of the squall line.The increase of DCAPE and the temperature laps rate in the lower troposphere which is almost equal to thedry-adiabat are both indicate the downburst′s coming.