GEOPHYSICAL MONOGRAPH SERIES, VOL. 147, PP. 49-69, 2004
Westerly wind events in the tropical Pacific and their influence on the coupled ocean-atmosphere system: A review
Observational and modeling aspects about Westerly Wind Events (WWEs) and their influence on the tropical Pacific ocean-atmosphere
system are reviewed. WWEs are a large part of the intraseasonal zonal wind activity over the warm pool. They have typical
amplitudes of 7 m s−1, zonal width of 20° longitude and duration of about 8 days. Their root causes are often a combination of various factors
including the Madden-Julian Oscillation, cold surges from mid-latitudes, tropical cyclones and other mesoscale phenomena.
The relationship between WWEs and the ENSO cycle is complex, involving among others the equatorial characteristics of the
WWEs, the oceanic background state and the internal atmospheric variability. Both observational and modeling studies demonstrate
that WWEs tend to cool the far western Pacific, shift the warm pool eastward and warm the central-eastern Pacific through
the generation of Kelvin waves. They are therefore important processes for the central and eastern Pacific warming during
the onset and development phase of El Niño. The strong atmospheric feedbacks that are likely to be generated by the ocean
response to WWEs even suggest that a single WWE is capable of establishing the conditions under which El Niño can occur. The
important role played by WWEs in the evolution and amplitude of recent El Niño events may therefore strongly limit the predictability
of El Niño.
Citation: Lengaigne, M.,