A Study On Weather Radar Bright-band

In stratiform precipitation, if an appropriate correction is not applied, the bright band(BB) that is induced by melting affection will cause significant overestimation in radarquantitative precipitation estimation (QPE). In this study, firstly, study the Bright Band (BB)microphysical characters using the Weather Research and Forecasting Model (WRFV3.2.1version) on one case of a trailing stratiform BB and another case of a stratiform embeddedconvective precipitation. Secondly, develop an algorithm that automatically corrects forlarge errors due to BB effects based on CINRAD-SA radar vertical profile of reflectivity(VPR) data, so that to improve a real-time weather radar derived QPE.（6） A conclusion from this study is that the bright band associated with thefreezing level is mainly caused by the melting of snowflakes and coalescence, and theincrease in the fall velocity of the scattering particles and the evaporation is the factorswhich contributes to the decrease in radar reflectivity below the bright band.（7） Through modeling the two cases of BB, we can find that relative to thestratiform embedded convective, the trailing stratiform BB has higher peak height, thickerthickness, and stronger intensity, and the two cases all have the nonuniform of BB instratiform. The melting of grapaul is the mainly reason for the trailing stratiform BB, andthe melting snow is the mainly reason for stratiform embedded convective.（8） Developed an algorithm that automatically corrects for large errors due to BBeffects based on CINRAD-SA radar vertical profile of reflectivity data. Firstly, as the greatdifference of VPR between stratiform and convection, a convective/stratiform precipitationclassification, which improved SHY95by adding three-dimensional reflectivity characters,is carried out before a VPR correction is applied. Then, a method that combines the meanapparent VPR computed from a volume scan of radar reflectivity observations and anidealized liner VPR model was used. As for the correction of BB, a method called rotationalcoordinate to identify the BB top and bottom heights more accurately is applied to smooththe BB.（9） What’s more, the BB height, thickness, and intensity which observed byBeijing, Tianjin, and Shijiazhuang Radar was analyzed.（10） BB take place more frequently in cool reason, like spring and autumn,meanwhile the freezing level is higher in summer by calculating the monthly mean freezinglevel (0oC isotherm) derived from nearby radiosonde observations of Beijing and Shijiazhuang from March to October in2000and2010,. Therefore, it is necessary toremove the affection of BB in QPE. The method described above is tested with twenty-sixevents that happened in different seasons in Beijing, Tianjin, and Shijiazhuang from2010to2011, and it is found that, after the correction of BB, the RMSE、 RMAE、 RMB ofradar-gauge pairs reduced significantly (respectively is1.78,0.44,0.45on average).