AREM-RUC 3h快速更新同化预报系统的建立与实时预报对比检验

Establishment and Real-time Forecasting Verification of AREM-RUC 3 h Rapid Update Assimilation and Forecast System

以AREM模式和LAPS系统为核心,建立了3 h快速更新同化预报系统(AREM-RUC),并对武汉暴雨研究所业务运行的三套模式系统(AREM-YW、AREM-SY和AREM-RUC)在2009年6—12月的实时降水预报结果进行了对比检验,结果表明:(1)2009年6月1日至12月14日00时起报的0～24 h降水预报TS评分AREM-RUC在全国、长江中下游、华南、华北、东北、西南地区东部的小、中、大、暴、大暴雨级别的降水评分均高于AREM-YW和AREM-SY。(2)从预报偏差来看,AREM-RUC对暴雨、大暴雨的预报范围比实况偏大;而AREM-YW和AREM-SY均比实况范围偏小。(3)对2009年6月17日湖北当阳局地大暴雨过程的实时预报AREM-RUC明显优于AREM-SY和AREM-YW,3 h不断更新的预报对改进降水落区和落时起到了积极作用。(4)对2009年6月29日长江中下游梅雨锋特大暴雨的实时预报,AREM-YW和AREM-SY预报强度明显偏弱,而AREM-RUC预报结果明显优于其他两个模式系统,预报的特大暴雨中心位置、强度均与实况有较好的对应。该过程实时预报结果也表明,在恰当的初值条件下,AREM模式有能力预报出与实况接近的特大暴雨过程。进一步分析表明,AREM-SY中采用的GRAPES_3DVAR同化方案分析的西太平洋副热带高压明显偏强偏西、水汽偏弱、中低层切变偏弱是导致AREM-SY降水预报偏弱、雨带偏北的原因。(5)对2009年6月29日特大暴雨过程每6 h降水结果的检验表明,3 h不断更新的预报对6 h累积降水量的预报有改善。

The 3 h rapid update assimilation and prediction system called AREM-RUC is built up based on AREM model and LAPS system,and the real-time forecasting performance,during the period from June to December 2009,was compared among AREM-YW,AREM-SY and AREM-RUC which are the three model systems running in operation at Institute of Heavy Rain of CMA.The results show that（1） the TS score of light rain,moderate rain,heavy rain and torrential rain forecasted by AREM-RUC leading 24h is higher than that of AREM-YW and AREM-SY in the area of China,the middle-lower valley of Yangtze River,south China,north China,northeast China,and eastern part of southwest China.（2） As to prediction deviation,the area of heavy rain forecasted by AREM-RUC is larger than the observation,but those by AREM-YW and AREM-SY are smaller than the observations.（3） The real-time forecast of AREM-RUC for a local heavy rain process happened in Dangyang in Hubei province on June 17,2009 is much better than those of AREM-SY and AREM-YW,and the prediction about rainfall area and time is improved greatly with 3h updated forecasts.（4） The AREM-RUC gives a much better forecast for an extremely heavy rain event happened on June 29,2009 with the location and intensity of the heavy rain center close to the observation,while the heavy rain intensity forecasts by AREM-YW and AREM-SY are much weaker than the observation.The further study shows that the GRAPES-3DVAR assimilation scheme adopted in AREM-SY gives an analysis of a westward and stronger Western Pacific Subtropical High,a weaker water vapor and a weaker low-level shear,which is the main reason why the rain belt forecasted by AREM-SY is weaker and to the north.（5） The verification of 6h rainfall forecast for the extremely heavy rain event on June 29,2009 suggests that the 3h updated forecast makes an improvement in the prediction of 6h accumulated precipitation.