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The effect of El Niño on intraseasonal Kelvin waves
Author(s) -
Benestad Rasmus E.,
Sutton Rowan T.,
Anderson David L. T.
Publication year - 2002
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/003590002320373292
Subject(s) - kelvin wave , climatology , dissipation , el niño southern oscillation , oscillation (cell signaling) , environmental science , atmospheric sciences , geology , physics , biology , genetics , thermodynamics
Intraseasonal Kelvin waves represent an important aspect of tropical ocean dynamics. There has been considerable speculation about whether intraseasonal Kelvin waves generated by intraseasonal wind events can trigger El Niño Southern Oscillation (ENSO) events, and therefore play a potentially important role in the prediction of El Niño. This study considers the different but related issue of how ENSO conditions influence intraseasonal Kelvin waves. Understanding this issue is an important part of clarifying the total role of scale interactions in the ENSO cycle. Numerical experiments carried out with an ocean general circulation model forced with European Centre for Medium‐Range Weather Forecasts re‐analysis surface fluxes show that both the west‐to‐east energy transmission and speed of propagation of intraseasonal Kelvin waves are strongly influenced by the phase of ENSO. The waves are much more strongly damped during La Niña conditions than during El Niño, primarily as a result of increased viscous dissipation associated with enhanced vertical shear. We suggest that this mechanism represents a significant source of nonlinearity between El Niño and La Niña states. It may influence the onset, the lifetime and the magnitude of warm or cold anomalies. Copyright © 2002 Royal Meteorological Society