The dynamics of error growth and predictability in a coupled model of ENSO

Andrew M. Moore, Richard Kleeman

Research output: Contribution to journalArticle

Abstract

Using new and emerging ideas about the growth of singular vectors (Optimal perturbations') in dynamical systems, the dynamics of error growth and predictability in an intermediate coupled model of the El Niño Southern Oscillation (ENSO) is investigated. A mechanism is identified for error growth associated with penetrative-convection anomalies in the atmosphere. Conditions for error growth via this mechanism are most favourable in the central Pacific where sea surface temperatures (SSTs) are relatively warm, and where changes in SST are moderately sensitive to vertical movements of the main oceanic thermocline. The singular vectors of the coupled system were computed using the tangent-linear coupled model and its adjoint. The singular-value spectrum was found to be dominated by one singular vector at all times of the year. The potential for error growth in the coupled model, measured in terms of the growth of energy of the dominant singular vector, is found to vary seasonally, being greatest during the boreal spring. These seasonal variations are associated with the seasonal cycle in SST. During boreal spring and early summer, the SST in the central Pacific is at its maximum, at which time conditions are most favourable for error growth. Springtime is also the time of the 'predictability barrier' for ENSO. The potential for error growth is also influenced by the ENSO cycle itself. The results suggest that error growth will be enhanced during the onset of El Niño and suppressed during the onset of La Niña, which indicates that El Niño may be less predictable than La Niña.

Original languageEnglish (US)
Pages (from-to)1405-1446
Number of pages42
JournalQuarterly Journal of the Royal Meteorological Society
Volume122
Issue number534
StatePublished - Jul 1996

Fingerprint

Southern Oscillation
sea surface temperature
vertical movement
thermocline
seasonal variation
convection
perturbation
anomaly
atmosphere
summer

Keywords

  • El Niño Southern Oscillation
  • Error growth
  • Ocean-atmosphere model
  • Predictability
  • Sea surface temperatures
  • Singular vectors

ASJC Scopus subject areas

  • Atmospheric Science
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

The dynamics of error growth and predictability in a coupled model of ENSO. / Moore, Andrew M.; Kleeman, Richard.

In: Quarterly Journal of the Royal Meteorological Society, Vol. 122, No. 534, 07.1996, p. 1405-1446.

Research output: Contribution to journalArticle

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