As part of NOAA＇s ＂Warn-On-Forecast＂ initiative, a convective-scale data assimilation and prediction system was developed using the WRF-ARW model and ARPS 3DVAR data assimilation technique. The system was then eval...As part of NOAA＇s ＂Warn-On-Forecast＂ initiative, a convective-scale data assimilation and prediction system was developed using the WRF-ARW model and ARPS 3DVAR data assimilation technique. The system was then evaluated using retrospective short-range ensemble analyses and probabilistic forecasts of the tornadic supercell outbreak event that occurred on 24 May 2011 in Oklahoma, USA. A 36-member multi-physics ensemble system provided the initial and boundary conditions for a 3-km convective-scale ensemble system. Radial velocity and reflectivity observations from four WSR-88 Ds were assimilated into the ensemble using the ARPS 3DVAR technique. Five data assimilation and forecast experiments were conducted to evaluate the sensitivity of the system to data assimilation frequencies, in-cloud temperature adjustment schemes, and fixed- and mixed-microphysics ensembles. The results indicated that the experiment with 5-min assimilation frequency quickly built up the storm and produced a more accurate analysis compared with the 10-min assimilation frequency experiment. The predicted vertical vorticity from the moist-adiabatic in-cloud temperature adjustment scheme was larger in magnitude than that from the latent heat scheme. Cycled data assimilation yielded good forecasts, where the ensemble probability of high vertical vorticity matched reasonably well with the observed tornado damage path. Overall, the results of the study suggest that the 3DVAR analysis and forecast system can provide reasonable forecasts of tornadic supercell storms.展开更多
为对延安市消雹和防灾减灾的工作提供指导,利用NCEP再分析资料、常规天气资料和延安C波段多普勒天气雷达资料详细分析2016年6月12日发生在延安安塞区特大冰雹过程,得到以下结论:(1)西北气流型天气形势配合着适宜的0℃层和-20℃层,为此...为对延安市消雹和防灾减灾的工作提供指导,利用NCEP再分析资料、常规天气资料和延安C波段多普勒天气雷达资料详细分析2016年6月12日发生在延安安塞区特大冰雹过程,得到以下结论:(1)西北气流型天气形势配合着适宜的0℃层和-20℃层,为此次大冰雹过程提供了良好的环境条件。(2)在雷达反射率因子上,此次强对流风暴表现出典型超级单体所具有的回波特征,包括风暴中低层的"V"型缺口、钩状回波、三体散射、有界弱回波区及中高层出现的回波悬垂现象,风暴发生到最强盛阶段反射率因子最大值高于65 d Bz且强中心高度在-20℃层之上。(3)过程中出现中气旋特征,中气旋维持1小时,最大厚度达到5 km,此次冰雹就发生在中尺度气旋处以及大风区一侧的风速辐合区。(4)垂直累积液态水含量(VIL)在发生冰雹前出现跃增变化,此次降雹后VIL没有突然下降,反而增大是由于风暴内存在多个强中心风暴持续发展导致。展开更多
基金provided by the NOAA/Office of Oceanic and Atmospheric Research under the NOAA–University of Oklahoma Cooperative Agreement#NA17RJ1227the U.S.Department of Commerce+2 种基金NSF AGS-1341878the National Natural Science Foundation of China(Project No.41305092)the International S&T Cooperation Program of China(ISTCP)(Grant No.2011DFG23210)
文摘As part of NOAA＇s ＂Warn-On-Forecast＂ initiative, a convective-scale data assimilation and prediction system was developed using the WRF-ARW model and ARPS 3DVAR data assimilation technique. The system was then evaluated using retrospective short-range ensemble analyses and probabilistic forecasts of the tornadic supercell outbreak event that occurred on 24 May 2011 in Oklahoma, USA. A 36-member multi-physics ensemble system provided the initial and boundary conditions for a 3-km convective-scale ensemble system. Radial velocity and reflectivity observations from four WSR-88 Ds were assimilated into the ensemble using the ARPS 3DVAR technique. Five data assimilation and forecast experiments were conducted to evaluate the sensitivity of the system to data assimilation frequencies, in-cloud temperature adjustment schemes, and fixed- and mixed-microphysics ensembles. The results indicated that the experiment with 5-min assimilation frequency quickly built up the storm and produced a more accurate analysis compared with the 10-min assimilation frequency experiment. The predicted vertical vorticity from the moist-adiabatic in-cloud temperature adjustment scheme was larger in magnitude than that from the latent heat scheme. Cycled data assimilation yielded good forecasts, where the ensemble probability of high vertical vorticity matched reasonably well with the observed tornado damage path. Overall, the results of the study suggest that the 3DVAR analysis and forecast system can provide reasonable forecasts of tornadic supercell storms.
文摘为对延安市消雹和防灾减灾的工作提供指导,利用NCEP再分析资料、常规天气资料和延安C波段多普勒天气雷达资料详细分析2016年6月12日发生在延安安塞区特大冰雹过程,得到以下结论:(1)西北气流型天气形势配合着适宜的0℃层和-20℃层,为此次大冰雹过程提供了良好的环境条件。(2)在雷达反射率因子上,此次强对流风暴表现出典型超级单体所具有的回波特征,包括风暴中低层的"V"型缺口、钩状回波、三体散射、有界弱回波区及中高层出现的回波悬垂现象,风暴发生到最强盛阶段反射率因子最大值高于65 d Bz且强中心高度在-20℃层之上。(3)过程中出现中气旋特征,中气旋维持1小时,最大厚度达到5 km,此次冰雹就发生在中尺度气旋处以及大风区一侧的风速辐合区。(4)垂直累积液态水含量(VIL)在发生冰雹前出现跃增变化,此次降雹后VIL没有突然下降,反而增大是由于风暴内存在多个强中心风暴持续发展导致。
