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The impact of eastern equatorial Pacific convection on the diversity of boreal winter El Niño teleconnection patterns

Abstract

It is widely recognized that no two El Niño episodes are the same; hence the predictable variations of the climate impacts associated with El Niño remain an open problem. Through an analysis of observational data and of large ensembles from six climate models forced by the observed time-varying sea surface temperatures (SSTs), this study raises the argument that the most fundamental predictable variations of boreal wintertime El Niño teleconnection patterns relate to the distinction between convective (EPC) and non-convective eastern Pacific (EPN) events. This distinction is a consequence of the nonlinear relationship between deep convection and eastern Pacific SSTs, and the transition to a convective eastern Pacific has a predictable relationship with local and tropical mean SSTs. Notable differences (EPC minus EPN) between the teleconnection patterns include positive precipitation differences over southern North America and northern Europe, positive temperature differences over northeast North America, and negative temperature differences over the Arctic. These differences are stronger and more statistically significant than the more common partitioning between eastern Pacific and central Pacific El Niño. Most of the seasonal mean composite anomalies associated with EPN El Niño are not statistically significant owing to the weak SST forcing and small sample sizes; however, the EPN teleconnection is more robust on subseasonal timescales following periods when the EPN pattern of tropical convection is active. These findings suggest that the differences between EPC and EPN climate impacts are physically robust and potentially useful for intraseasonal forecasts for lead times of up to a few weeks.

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Acknowledgments

We are grateful for stimulating discussions with Dr. Steven Feldstein, Dr. Sukyoung Lee, and Ms. Michelle L’Heureux, which enhanced this work. We also thank Dr. Andrew Wittenberg, Dr. Xiaosong Yang, and two anonymous reviewers for constructive comments that resulted in significant improvements of the manuscript. NCJ was supported by NOAA’s Climate Program Office, which includes a grant from the Modeling, Analysis, Predictions, and Projections program, award number NA14OAR4310189. YK was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan through Grant-in-Aid for Young Scientists 15H05466 and by the Japanese Ministry of Environment through the Environment Research and Technology Development Fund 2-1503. NCEP–NCAR reanalysis and FACTS climate model simulation data are provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd.

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Correspondence to Nathaniel C. Johnson.

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Johnson, N.C., Kosaka, Y. The impact of eastern equatorial Pacific convection on the diversity of boreal winter El Niño teleconnection patterns. Clim Dyn 47, 3737–3765 (2016). https://doi.org/10.1007/s00382-016-3039-1

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  • DOI: https://doi.org/10.1007/s00382-016-3039-1

Keywords

  • El Niño
  • Teleconnection patterns
  • Pacific/North American pattern
  • Convective threshold
  • Eastern Pacific
  • Subseasonal-to-seasonal climate prediction
  • Arctic amplification