气象学报Issue(4)：658-677,20.DOI:10.11676/qxxb2014.070
雷达径向风观测在华北区域数值预报系统中的实时三维变分同化应用试验
The real-time radar radial velocity 3DVar assimilation experiments for application to an operational forecast model in North China
摘要
Abstract
In recent years,research efforts have been carried out to develop the radar data pre-processing system and assimila-ting strategy for the purpose of future operational implementation for BJ-RUCv2.0.There are 4 S-band and 2 C-band Doppler radars involved in this study,comprising the operation radar network in North China.A radar data preprocessing system was built on the base of the counterpart of VDRAS with the functions to perform quality control,mapping and error statistics.With techniques of tuning the background error covariance (BE)and length scales developed,a two-step scheme was designed to as-similate radial velocity along with other conventional observations.The pre-operational experiments of BJ-RUCv2.0 with as-similation of radial velocity were performed during the flooding season from 1 June to 31 August 2011.The results were evalua-ted and compared along with another identical experiment running in parallel but without assimilation of radial velocity.Moni-toring on quality of the radial velocity data entering the data assimilation (DA)system revealed that the DA system effectively absorbed the information brought by the radial velocity and generated reasonable analysis increments.But obviously,the valid amount,data quality and reliability of radial velocity observations from S-band radars were much better than C-band radars. The evaluations for cycling forecasts for both experiments were performed against conventional surface and radiosonde observa-tions.In general,from the 3-month results,no significant improvements were indeed found against conventional observations because of the localized impact of radial velocities in space and time.But more positive signals were shown by precipitation fore-cast skills,especially for short-term forecasts and the precipitations with larger intensities.The cases of a squall line and a local-forced convection were selected for more detailed discussion respectively.It was found that the more the assimilation time of ra-dar radial velocity approached the occurrence time of convection,the more significantly the precipitation forecast skill was im-proved.For the well-organized convection such as squall line,the modification of low-level dynamical conditions brought by the assimilation of radial velocity was the key factor of the improvement of forecast.For the local-forced convections,the more fa-vorable thermal circumstances were also built along with the modification of dynamical conditions.But it is still needed to be noted that,it is usually at the approaching time of convection that the effect of radial velocity assimilation gets to be more prominent.关键词
雷达径向风/资料同化/三维变分/背景场误差协方差Key words
Radar radial velocity/Data assimilation (DA)/3DVar/Background error covariance (BE)分类
天文与地球科学引用本文复制引用
陈敏,陈明轩,范水勇..雷达径向风观测在华北区域数值预报系统中的实时三维变分同化应用试验[J].气象学报,2014,(4):658-677,20.基金项目
资助课题国家重点基础研究发展计划973项目（2013CB430100）、北京市科委绿色通道项目（Z090506016609001）、国家科技支撑计划课题（2008BAC37B03）。 （）
