基于一个中等复杂程度模式(ICM)集合预报系统(EPS)产生的海表温度距平(SSTA)预报产品,从误差增长的角度探讨了2015/16超强El Nio事件的"春季可预报性障碍"(SPB)问题.通过分析集合预报成员预报误差的增长倾向,发现了2015/16 ...基于一个中等复杂程度模式(ICM)集合预报系统(EPS)产生的海表温度距平(SSTA)预报产品,从误差增长的角度探讨了2015/16超强El Nio事件的"春季可预报性障碍"(SPB)问题.通过分析集合预报成员预报误差的增长倾向,发现了2015/16 El Nio事件的预报误差增长呈现显著的季节依赖性,且在春/夏季具有最大增长率,表明ICM-EPS对2015/16 El Nio事件的预报发生了明显的SPB现象.进一步分析表明,上述SPB现象不是由ICM初始场的不确定性引起,而是由其模式误差导致,而ICM-EPS集合预报成员的平均滤掉了部分模式误差的影响,减弱了SPB现象,从而使得2015/16 El Nio事件的预报产生较小的预报误差.通过探讨由海温方程的倾向误差表征的模式误差,该研究揭示了导致SPB现象发生的倾向误差的主要空间特征,并阐明了ICM-EPS低估2015/16El Nio事件强度的原因.此外,本文也揭示了导致显著SPB现象,尤其是导致最大预报误差的SSTA倾向误差的结构特征.该倾向误差的SSTA分量具有赤道中东太平洋负异常,西太平洋正异常的纬向偶极子结构,与Duan等提出的最敏感非线性强迫奇异向量(NFSV)-倾向误差高度相似,从而表明NFSV-型倾向误差也存在于实际的El Nio预报中.该研究也探讨了其他超强El Nio事件,如1982/83和1997/98事件,得到了类似的结果.因此,如果利用NFSV-型倾向误差校正ICM模式误差,ICM-EPS可大大提高超强El Nio事件的预报技巧.展开更多
Using predictions for the sea surface temperature anomaly(SSTA) generated by an intermediate coupled model(ICM)ensemble prediction system(EPS), we first explore the "spring predictability barrier"(SPB) probl...Using predictions for the sea surface temperature anomaly(SSTA) generated by an intermediate coupled model(ICM)ensemble prediction system(EPS), we first explore the "spring predictability barrier"(SPB) problem for the 2015/16 strong El Nio event from the perspective of error growth. By analyzing the growth tendency of the prediction errors for ensemble forecast members, we conclude that the prediction errors for the 2015/16 El Nio event tended to show a distinct season-dependent evolution, with prominent growth in spring and/or the beginning of the summer. This finding indicates that the predictions for the 2015/16 El Nio occurred a significant SPB phenomenon. We show that the SPB occurred in the 2015/16 El Nio predictions did not arise because of the uncertainties in the initial conditions but because of model errors. As such, the mean of ensemble forecast members filtered the effect of model errors and weakened the effect of the SPB, ultimately reducing the prediction errors for the 2015/16 El Nio event. By investigating the model errors represented by the tendency errors for the SSTA component,we demonstrate the prominent features of the tendency errors that often cause an SPB for the 2015/16 El Nio event and explain why the 2015/16 El Nio was under-predicted by the ICM EPS. Moreover, we reveal the typical feature of the tendency errors that cause not only a significant SPB but also an aggressively large prediction error. The feature is that the tendency errors present a zonal dipolar pattern with the west poles of positive anomalies in the equatorial western Pacific and the east poles of negative anomalies in the equatorial eastern Pacific. This tendency error bears great similarities with that of the most sensitive nonlinear forcing singular vector(NFSV)-tendency errors reported by Duan et al. and demonstrates the existence of an NFSV tendency error in realistic predictions. For other strong El Nio events, such as those that occurred in 1982/83 and 1997/98, we obtain the tendency errors of the NFSV structure, which cause a significant SPB and yield a much larger prediction error. These results suggest that the forecast skill of the ICM EPS for strong El Nio events could be greatly enhanced by using the NFSV-like tendency error to correct the model.展开更多
文摘基于一个中等复杂程度模式(ICM)集合预报系统(EPS)产生的海表温度距平(SSTA)预报产品,从误差增长的角度探讨了2015/16超强El Nio事件的"春季可预报性障碍"(SPB)问题.通过分析集合预报成员预报误差的增长倾向,发现了2015/16 El Nio事件的预报误差增长呈现显著的季节依赖性,且在春/夏季具有最大增长率,表明ICM-EPS对2015/16 El Nio事件的预报发生了明显的SPB现象.进一步分析表明,上述SPB现象不是由ICM初始场的不确定性引起,而是由其模式误差导致,而ICM-EPS集合预报成员的平均滤掉了部分模式误差的影响,减弱了SPB现象,从而使得2015/16 El Nio事件的预报产生较小的预报误差.通过探讨由海温方程的倾向误差表征的模式误差,该研究揭示了导致SPB现象发生的倾向误差的主要空间特征,并阐明了ICM-EPS低估2015/16El Nio事件强度的原因.此外,本文也揭示了导致显著SPB现象,尤其是导致最大预报误差的SSTA倾向误差的结构特征.该倾向误差的SSTA分量具有赤道中东太平洋负异常,西太平洋正异常的纬向偶极子结构,与Duan等提出的最敏感非线性强迫奇异向量(NFSV)-倾向误差高度相似,从而表明NFSV-型倾向误差也存在于实际的El Nio预报中.该研究也探讨了其他超强El Nio事件,如1982/83和1997/98事件,得到了类似的结果.因此,如果利用NFSV-型倾向误差校正ICM模式误差,ICM-EPS可大大提高超强El Nio事件的预报技巧.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41230420 & 41525017)the National Public Benefit (Meteorology) Research Foundation of China (Grant No. GYHY201306018)
文摘Using predictions for the sea surface temperature anomaly(SSTA) generated by an intermediate coupled model(ICM)ensemble prediction system(EPS), we first explore the "spring predictability barrier"(SPB) problem for the 2015/16 strong El Nio event from the perspective of error growth. By analyzing the growth tendency of the prediction errors for ensemble forecast members, we conclude that the prediction errors for the 2015/16 El Nio event tended to show a distinct season-dependent evolution, with prominent growth in spring and/or the beginning of the summer. This finding indicates that the predictions for the 2015/16 El Nio occurred a significant SPB phenomenon. We show that the SPB occurred in the 2015/16 El Nio predictions did not arise because of the uncertainties in the initial conditions but because of model errors. As such, the mean of ensemble forecast members filtered the effect of model errors and weakened the effect of the SPB, ultimately reducing the prediction errors for the 2015/16 El Nio event. By investigating the model errors represented by the tendency errors for the SSTA component,we demonstrate the prominent features of the tendency errors that often cause an SPB for the 2015/16 El Nio event and explain why the 2015/16 El Nio was under-predicted by the ICM EPS. Moreover, we reveal the typical feature of the tendency errors that cause not only a significant SPB but also an aggressively large prediction error. The feature is that the tendency errors present a zonal dipolar pattern with the west poles of positive anomalies in the equatorial western Pacific and the east poles of negative anomalies in the equatorial eastern Pacific. This tendency error bears great similarities with that of the most sensitive nonlinear forcing singular vector(NFSV)-tendency errors reported by Duan et al. and demonstrates the existence of an NFSV tendency error in realistic predictions. For other strong El Nio events, such as those that occurred in 1982/83 and 1997/98, we obtain the tendency errors of the NFSV structure, which cause a significant SPB and yield a much larger prediction error. These results suggest that the forecast skill of the ICM EPS for strong El Nio events could be greatly enhanced by using the NFSV-like tendency error to correct the model.