Season-dependent forecast skill of the dominant atmospheric circulation patterns

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• 作者：XiaoJing JiaHai LinJune-Yi LeeBin Wang
• 会议时间：2013-10-01
• 关键词：seasonal forecast ; numerical model ; MME
• 作者单位：XiaoJing Jia(Department of Earth Sciences,ZheJiang University,HangZhou,ZheJiang,China)Hai Lin(Recherche en Pr_evision Num_erique,Environment Canada,Dorval,Quebec,Canada)June-Yi Lee,Bin Wang(International Pacific Research Center and Department of Meteorology,University of Hawaii,Honolulu,USA)
• 母体文献：第十届长三角气象科技论坛论文集
• 会议名称：第十届长三角气象科技论坛
• 会议地点：浙江安吉
• 主办单位：中国气象学会
• 语种：chi

摘要

Multi-model ensemble (MME) seasonal forecasts are analyzed to evaluate numerical models' performance in predicting the leading forced atmospheric circulation pattern over the extratropical Northern Hemisphere.Results show that the time evolution of the leading tropical Pacific sea surface temperature (SST)-coupled atmospheric pattern (MCA1),which is obtained by applying a maximum covariance analysis (MCA) between 500-hPa geopotential height (Z500) in the extratropical Northern Hemisphere and SST in the tropical Pacific Ocean,can be predicted with a significant skill in MAM,JJA and DJF one-month ahead.However,most models perform poorly in capturing the time variation of MCA1 in SON with August 1st initial condition.Two possible reasons for the models' low skill in SON are identified.Firstly,the models have the most pronounced errors in the mean state of SST and precipitation along the central equatorial Pacific.Due to the link between the divergent circulation forced by tropical heating and the midlatitude atmospheric circulation,errors in the mean state of tropical SST and precipitation may lead to a degradation of midlatitude forecast skill.Secondly,examination of the potential predictability of the atmosphere,estimated by the ratio of the total variance to the variance of the model forecasts due to internal dynamics,shows that the atmospheric potential predictability over the North Pacific-North American (NPNA) region is the lowest in SON comparing to the other three seasons.The low ratio in SON is due to a low variance associated with external forcing and a high variance related to atmospheric internal processes over this area.