title: A new Approach to El Niño Prediction beyond the Spring Season.
abstract: The enormous societal importance of accurate El Niño forecasts has long been recognized. Nonetheless, our predictive capabilities were once more shown to be inadequate in 2014 when an El Nino event was widely predicted by international climate centers but failed to materialize. This result highlighted the problem of the opaque spring persistence barrier, which severely restricts longer-term, accurate forecasting beyond boreal spring. Here we show that the role played by tropical seasonality in the evolution of the El Niño is changing on pentadal (five-year) to decadal timescales and thus that El Niño predictions beyond boreal spring will inevitably be uncertain if this change is neglected. To address this problem, our new coupled climate simulation incorporates these long-term influences directly and generates accurate hindcasts for the 7 major historical El Niños. The error value between predicted and observed sea surface temperature (SST) in a specific tropical region (5°N-5°S and 170°-120°W) can consequently be reduced by 0.6 Kelvin for one-year predictions. This correction is substantial since an "El Niño" is confirmed when the SST anomaly becomes greater than +0.5 Kelvin. Our 2014 forecast is in line with the observed development of the tropical climate.
authors.affiliation: Research and Development Center for Global Change, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Masuda
authors.affiliation: Environmental Satellite Applications, Llys Awel, Mount Street, Menai Bridge LL595BW, UK.|Institute of Liberal Arts and Sciences, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: John Philip
authors.initials: JP
authors.lastname: Matthews
authors.affiliation: The Center for Earth Information Science and Technology, JAMSTEC, Yokohama 236-0001, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ishikawa
authors.affiliation: Project Team for Risk Information on Climate Change, JAMSTEC, Yokohama 236-0001, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Mochizuki
authors.affiliation: The Center for Earth Information Science and Technology, JAMSTEC, Yokohama 236-0001, Japan.
authors.forename: Yuusuke
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Headquarters, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Awaji