El Nino/Southern Oscillation Research

This page describes ongoing research on the El Nino-Southern Oscialltion, more commonly known as the El Nino and La Nina phenomenons. El Nino and La Nina are coupled atmosphere-ocean interactions centered in the tropical Pacific that has impact on global weather patterns.

Ed Harrison and Sim Larkin have been working to detail the lifecycles of El Nino and La Nina events since the mid-1990s. This work has resulted in the first description of the statistically significant weather impacts of El Nino and La Nina events, the first description of the robust lifecycles of El Nino, La Nina, and their assymetries, and discussion of the importance of the exact definition of El Nino and La Nina to their usefulness.

Research: Global Lifecycles of El Nino and La Nina U.S. Seasonal Weather Impacts Global Seasonal Weather Impacts Implications of ENSO defintion Paper References and PDFs

Data Access and Maps: View El Nino Composite Maps - global lifecycles, U.S. and global weather imapcts View UPDATED El Nino Composite Maps (including 1997 El Nino event)

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Global Lifecycles of El Nino and La Nina Events

Our work has shown that El Nino and La Nina events have robust lifecycles of sea surface temperature, sea level pressure, and surface wind patterns that occur in all or nearly all events.

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Papers in this series are:

• First description of the robust El Nino SLP lifecycle
  Harrison and Larkin, 1996; J. Climate
• First description of the robust El Nino SST, wind, (and SLP) lifecycle
  Harrison and Larkin, 1998; Rev. of Geophys
• First description of the robust La Nina lifecycle
  Larkin and Harrison, 2002; J. Climate
• Comparison of El Nino and La Nina lifecycles
  Larkin and Harrison, 2005; J. Climate
• Comparison of the 1997-98 El Nino event with previous events
  Larkin and Harrison, 2008; J. Climate (in review)

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U.S. Seasonal Weather Impacts

Our work was the first to document the statistically significant seasonal weather associations with El Nino and La Nina.

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Papers in this series are:

• First description of the statistically significant El Nino / U.S. seasonal weather associations
  Harrison and Larkin, 1998; GRL
• First description of the statistically significant La Nina / U.S. seasonal weather associations
  Harrison and Larkin, 2002; book chapter in "La Nina"
• Implications of new El Nino definition on U.S. / El Nino seasonal weather associations
  Larkin and Harrison, 2005a; GRL

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Global Seasonal Weather Impacts

Our work has shown the statistically significant coarse scale global seasonal weather impacts and their connection with the definition of El Nino.

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Papers in this series are:

• Implications of El Nino definition on global El Nino impacts
  Larkin and Harrison, 2005b; GRL
• Comparison of the 1997-98 El Nino with previous events
  Larkin and Harrison, 2008; J. Climate (in review)

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El Nino Definition

Our work showed that the 2003 El Nino definition adopted by NOAA and the WMO Region IV had negative impacts on seasonal weather associations with El Nino, thereby reducing the statistical signficance of El Nino for seasonal forecasting. Since this work NOAA has altered the way it uses El Nino impacts in seasonal forecasting.

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Papers in this series are:

• Implications for U.S. seasonal weather associations
  Larkin and Harrison, 2005a; GRL
• Implications for global seasonal weather associations
  Larkin and Harrison, 2005b; GRL

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Complete ENSO Paper List

• Harrison D.E., Larkin N.K. 1996. The COADS sea level pressure signal: a near-global El Niño composite and time series view, 1946-1993. J. Climate, 9 (12), 3025-3055. PDF
• Harrison D.E., Larkin N.K. 1998. Seasonal U.S. temperature and precipitation anomalies associated with El Niño: Historical results and comparison with 1997-98. Geophys. Res. Lett., 25 (21), 3959-3962. PDF
• Harrison, D.E., and N.K. Larkin. 1998. El Niño-Southern Oscillation sea surface temperature and wind anomalies. Rev. of Geophys, 36 (3), 353-399. PDF
• Larkin N.K. 2000. Ph.D. Thesis: ENSO warm (El Niño) and cold (La Niña) events: global historical patterns, symmetries, asymmetries, and their implications. University of Washington School of Oceanography, Seattle, Washington. 317pp.
• Larkin N.K., Harrison D.E. 2001. Tropical Pacific ENSO cold events, 1946-1995: SST, SLP and surface wind composite anomaly patterns. J. Climate, 14, 3904-3931. PDF
• Harrison D.E., Larkin N.K. 2001. Comments on Smith et al. (1999) ?Comparison of 1997-98 U.S. temperature and precipitation anomalies to historical ENSO warm phases.? J. Climate, 14, 1894-1895.
• Harrison D.E., Larkin N.K. 2002. Cold events: anti-El Niño? In: Cold Events, ed. M. Glantz, United Nations Univ. Press., Tokyo, Japan, pp. 237-241.
• Larkin N.K., Harrison D.E. 2002. ENSO Warm (El Niño) and Cold (La Niña) event life cycles: ocean surface anomaly patterns, their symmetries, asymmetries, and implications. J. Climate, 15, 1118-1140. PDF
• Larkin N.K., Harrison D.E. 2005. ?On the definition of El Niño and associated seasonal average U.S. weather anomalies.? Geophys. Res. Lett., 32, L13705, doi:10.1029/2005GL022738. PDF
• Larkin N. K., Harrison D.E. 2005. ?Global seasonal temperature and precipitation anomalies during El Niño autumn and winter.? Geophys. Res. Lett., 32, L16705, doi:10.1029/2005GL022860. PDF