中国地区NCEP再分析资料与台站观测的地表温度差异及其影响

作为时间序列非线性的一个重要指标,从NCEP再分析得到日气温异常的时间不可逆性(TI)与观测站的相比几乎一致地被高估了.因为非线性与可预报性/极端事件之间有着密切的关系,除了高估的TI外,这些大气测度也可能被高估.本文结果表明:NCEP再分析的日最低和最高气温异常序列的内在可预报性,预报技巧和极端事件发生次数也几乎一致被高估.而且,这些高估的测度与高估的TI只存在微弱的相关性,这表明利用NCEP再分析研究可预测性和极端事件时,需要仔细考虑其质量对结论的可能影响.

Discrepancies in surface temperature between NCEP reanalysis data and station observations over China and their implications

Previous studies show that temporal irreversibility (TI),as an important indicator of the nonlinearity of time series,is almost uniformly overestimated in the daily air temperature anomaly series over China in NCEP reanalysis data,as compared with station observations.Apart from this highly overestimated TI in the NCEP reanalysis,some other important atmospheric metrics,such as predictability and extreme events,might also be overestimated since there are close relations between nonlinearity and predictability/extreme events.In this study,these issues are fully addressed,i.e.,intrinsic predictability,prediction skill,and the number of extreme events.The results show that intrinsic predictability,prediction skill,and the occurrence number of extreme events are also almost uniformly overestimated in the NCEP reanalysis daily minimum and maximum air temperature anomaly series over China.Furthermore,these overestimations of intrinsic predictability,prediction skill,and the number of extreme events are only weakly correlated with the overestimated TI,which indicates that the quality of the NCEP reanalysis should be carefully considered when conclusions on both predictability and extreme events are derived.