摘要
The skill of most ENSO prediction models has declined significantly since 2000.This decline may be due to a weakening of the correlation between tropical predictors and ENSO.Moreover,the effects of extratropical ocean variability on ENSO have increased during this period.To improve ENSO predictability,the authors investigate the influence of the extratropical Atlantic and Pacific oceans on ENSO during the pre-2000 and post-2000 periods,and find that the influence of the northern tropical Atlantic sea surface temperature(NTA SST)on ENSO has significantly increased since 2000.Furthermore,there is a much earlier and stronger correlation between NTA SST and ENSO over the central-eastern Pacific during June-July-August in the post-2000 period compared with the pre-2000 period.The extratropical Pacific SST predictors for ENSO retain an approximate 10-month lead time after 2000.The authors use SST signals in the extratropical Atlantic and Pacific to predict ENSO using a statistical prediction model.This results in a significant improvement in ENSO prediction skill and an obvious decrease in the spring predictability barrier phenomenon of ENSO.These results indicate that extratropical Atlantic and Pacific SSTs can make substantial contributions to ENSO prediction,and can be used to enhance ENSO predictability after 2000.
本文利用1979–2017年的再分析逐月资料,首先探讨了2000年前后ENSO海温(Niño3.4指数)与太平洋和其他海域的ENSO海温前兆信号(WWV:VM:vSPQ:NTA SST)之间的关系变化。结果表明由于热带太平洋信号WWV自身方差的骤减,WWV在2000年后并不能在超前6个月以上成为一个很好的预测因子;而南北太平洋区域的海温信号(VM:SPQ)与Niño3.4指数的超前关系保持稳定:值得注意的是,NTA SST与ENSO之间的关系较2000年前更好,且仍有增强趋势。其次,结合分析结果,将热带外ENSO前兆信号加入到一个ENSO统计预测模型之中,原模型预测技巧均得到提升,超前一年左右的时间预测结果与观测相关系数均大于0.7,并且在一定程度上降低了原模型的春季可预报障碍(SPB)现象的强度。
基金
This research was supported by the National Natural Science Foundation of China[grant number 41975070]
the Identification and mechanism study of global warming‘hiatus’phenomenon of 973 project of China[grant number 2016YFA0601801].
