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Assimilation of Doppler Radar Data with an Ensemble 3DEnVar Approach to Improve Convective Forecasting
作者姓名:Shibo GAO  Haiqiu YU  Chuanyou REN  Limin LIU  Jinzhong MIN
作者单位:Department of Atmospheric Sciences,Agronomy College,Shenyang Agricultural University,Shenyang 110866,China;Department of Atmospheric Sciences,Agronomy College,Shenyang Agricultural University,Shenyang 110866,China;Department of Atmospheric Sciences,Agronomy College,Shenyang Agricultural University,Shenyang 110866,China;Department of Atmospheric Sciences,Agronomy College,Shenyang Agricultural University,Shenyang 110866,China;School of Atmospheric Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China
基金项目:This research was supported by the Startup Foundation for Introducing Talent of Shenyang Agricultural University
摘    要:An ensemble three-dimensional ensemble-variational(3DEnVar)data assimilation(E3DA)system was developed within the Weather Research and Forecasting model’s 3DVar framework to assimilate radar data to improve convective forecasting.In this system,ensemble perturbations are updated by an ensemble of 3DEnVar and the ensemble forecasts are used to generate the flow-dependent background error covariance.The performance of the E3DA system was first evaluated against one experiment without radar DA and one radar DA experiment with 3DVar,using a severe storm case over southeastern China on 5 June 2009.Results indicated that E3DA improved the quantitative forecast skills of reflectivity and precipitation,as well as their spatial distributions in terms of both intensity and coverage over 3DVar.The root-mean-square error of radial velocity from 3DVar was reduced by E3DA,with stronger low-level wind closer to observation.It was also found that E3DA improved the wind,temperature and water vapor mixing ratio,with the lowest errors at the surface and upper levels.3DVar showed moderate improvements in comparison with forecasts without radar DA.A diagnosis of the analysis revealed that E3DA increased vertical velocity,temperature,and humidity corresponding to the added reflectivity,while 3DVar failed to produce these adjustments,because of the lack of reasonable cross-variable correlations.The performance of E3DA was further verified using two convective cases over southern and southeastern China,and the reflectivity forecast skill was also improved over 3DVar.

关 键 词:ensemble  3DEnVar  3DVAR  radar  data  assimilation  convective  forecasting

Assimilation of Doppler Radar Data with an Ensemble 3DEnVar Approach to Improve Convective Forecasting
Shibo GAO,Haiqiu YU,Chuanyou REN,Limin LIU,Jinzhong MIN.Assimilation of Doppler Radar Data with an Ensemble 3DEnVar Approach to Improve Convective Forecasting[J].Advances in Atmospheric Sciences,2021,38(1):132-146.
Authors:Shibo GAO  Haiqiu YU  Chuanyou REN  Limin LIU  Jinzhong MIN
Institution:Department of Atmospheric Sciences,Agronomy College,Shenyang Agricultural University,Shenyang 110866,China;School of Atmospheric Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China
Abstract:An ensemble three-dimensional ensemble-variational(3DEnVar) data assimilation(E3DA) system was developed within the Weather Research and Forecasting model's 3DVar framework to assimilate radar data to improve convective forecasting. In this system, ensemble perturbations are updated by an ensemble of 3DEnVar and the ensemble forecasts are used to generate the flow-dependent background error covariance. The performance of the E3DA system was first evaluated against one experiment without radar DA and one radar DA experiment with 3DVar, using a severe storm case over southeastern China on 5 June 2009. Results indicated that E3DA improved the quantitative forecast skills of reflectivity and precipitation, as well as their spatial distributions in terms of both intensity and coverage over 3DVar. The root-mean-square error of radial velocity from 3DVar was reduced by E3DA, with stronger low-level wind closer to observation. It was also found that E3DA improved the wind, temperature and water vapor mixing ratio, with the lowest errors at the surface and upper levels. 3DVar showed moderate improvements in comparison with forecasts without radar DA. A diagnosis of the analysis revealed that E3DA increased vertical velocity, temperature, and humidity corresponding to the added reflectivity, while 3DVar failed to produce these adjustments, because of the lack of reasonable cross-variable correlations. The performance of E3DA was further verified using two convective cases over southern and southeastern China, and the reflectivity forecast skill was also improved over 3DVar.
Keywords:ensemble 3DEnVar  3DVar  radar data assimilation  convective forecasting
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