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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Resonant Wave Interactions in the Equatorial Waveguide

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Raupp, Carlos F. M. [1] ; Dias, Pedro L. Silva [1] ; Tabak, Esteban G. [2] ; Milewski, Paul [3]
Total Authors: 4
[1] Univ Sao Paulo, Dept Atmospher Sci, Inst Astron Geophys & Atmospher Sci, BR-05508 Sao Paulo - Brazil
[2] NYU, Courant Inst Math Sci, New York, NY - USA
[3] Univ Wisconsin, Dept Math, Madison, WI 53706 - USA
Total Affiliations: 3
Document type: Journal article
Source: JOURNAL OF THE ATMOSPHERIC SCIENCES; v. 65, n. 11, p. 3398-3418, NOV 2008.
Web of Science Citations: 9

Weakly nonlinear interactions among equatorial waves have been explored in this paper using the adiabatic version of the equatorial beta-plane primitive equations in isobaric coordinates. Assuming rigid lid vertical boundary conditions, the conditions imposed at the surface and at the top of the troposphere were expanded in a Taylor series around two isobaric surfaces in an approach similar to that used in the theory of surface-gravity waves in deep water and capillary-gravity waves. By adopting the asymptotic method of multiple time scales, the equatorial Rossby, mixed Rossby-gravity, inertio-gravity, and Kelvin waves, as well as their vertical structures, were obtained as leading-order solutions. These waves were shown to interact resonantly in a triad configuration at the O(epsilon) approximation. The resonant triads whose wave components satisfy a resonance condition for their vertical structures were found to have the most significant interactions, although this condition is not excluding, unlike the resonant conditions for the zonal wavenumbers and meridional modes. Thus, the analysis has focused on such resonant triads. In general, it was found that for these resonant triads satisfying the resonance condition in the vertical direction, the wave with the highest absolute frequency always acts as an energy source (or sink) for the remaining triad components, as usually occurs in several other physical problems in fluid dynamics. In addition, the zonally symmetric geostrophic modes act as catalyst modes for the energy exchanges between two dispersive waves in a resonant triad. The integration of the reduced asymptotic equations for a single resonant triad shows that, for the initial mode amplitudes characterizing realistic magnitudes of atmospheric flow perturbations, the modes in general exchange energy on low-frequency (intraseasonal and/or even longer) time scales, with the interaction period being dependent upon the initial mode amplitudes. Potential future applications of the present theory to the real atmosphere with the inclusion of diabatic forcing, dissipation, and a more realistic background state are also discussed. (AU)

FAPESP's process: 02/09683-9 - Impact of non-linearity of the interaction between the tropical and extratropical atmospheric circulations
Grantee:Carlos Frederico Mendonça Raupp
Support type: Scholarships in Brazil - Doctorate