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A possible role for unstable coupled waves affected by resonance between Kelvin waves and seasonal warming in the development of the strong 1997-1998 El NiA[+ or -]o

Authors :
Toyoda, T.
Masuda, S.
Sugiura, N.
Mochizuki, T.
Igarashi, H.
Kamachi, M.
Ishikawa, Y.
Awaji, T.
Source :
Deep-Sea Research. Part I, Oceanographic Research Papers. April, 2009, Vol. 56 Issue 4, p495, 18 p.
Publication Year :
2009

Abstract

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2008.12.002 Byline: T. Toyoda (a), S. Masuda (a), N. Sugiura (a), T. Mochizuki (a), H. Igarashi (b), M. Kamachi (c), Y. Ishikawa (d), T. Awaji (a)(d) Keywords: Air-sea coupled process; El NiA[+ or -]o; Data assimilation; 4D-VAR Abstract: Time-varying air-sea coupled processes in the central to eastern equatorial Pacific associated with strong El NiA[+ or -]o development during the 1997-1998 period are examined using a newly developed reanalysis dataset obtained from four-dimensional variational ocean-atmosphere coupled data assimilation experiments. The time series of this data field exhibits realistic features of El NiA[+ or -]o evolution. Our analysis indicates that resonance between eastward-propagating oceanic downwelling Kelvin waves and the seasonal rise of sea-surface temperature (SST) in the central to eastern equatorial Pacific generates relatively persistent high SST conditions accompanied by a deeper thermocline and more relaxed easterly winds than usual. The surface condition resulting from the wave-seasonal SST resonance represents a preconditioned state that leads to an enhancement in incident downwelling Kelvin waves to levels sufficient to induce large-amplitude unstable coupled waves in the central to eastern equatorial region. Heat balance estimates using our reanalysis dataset suggest that the unstable coupled waves are categorized within the intermediate regime of coupled Kelvin and Rossby waves and have the potential to grow rapidly. We argue that the seasonal resonance and the unstable coupled waves should play crucial roles in the development of the largest historical El NiA[+ or -]o event, which was recorded between late 1997 and early 1998. Author Affiliation: (a) Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan (b) Marine-Earth Data and Information Department, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan (c) Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan (d) Department of Geophysics, Graduate School of Science, Kyoto University, Kyoto, Japan Article History: Received 29 December 2007; Revised 1 December 2008; Accepted 4 December 2008

Details

Language :
English
ISSN :
09670637
Volume :
56
Issue :
4
Database :
Gale General OneFile
Journal :
Deep-Sea Research. Part I, Oceanographic Research Papers
Publication Type :
Academic Journal
Accession number :
edsgcl.195077091