Seminário: Nonlinear Interaction of Kelvin and Eastward Yanai Waves in the Equatorial Waveguide

11/12/2015 - 14:00
Auditório 2 do IAG (Rua do Matão, 1226, Cidade Universitária)

O seminário do Departamento de Ciências Atmosféricas será apresentado pelo Prof. Dr. Carlos Mendonça Raupp (ACA/IAG/USP).

Nonlinear Interaction of Kelvin and Eastward Yanai Waves in the Equatorial Waveguide
Equatorially trapped wave motion is a remarkable feature of tropical dynamics. Since the pioneering work of [1], observational evidence of the equatorial wave types has been analyzed in last decades, and space-time power spectra of these waves have been obtained (e.g., see [2]). These observational studies have shown significant spectral peak bands in intermediate to short spatial scales for both tropospheric Kelvin and eastward propagating Yanai waves. Here we attempt to provide a possible theoretical explanation for these observed spectral peak bands. 
 Large and planetary scale Kelvin waves are believed to be excited by deep convection forcing (e.g., see [3]). Consequently, a possible conjecture for explaining the excitation of intermediate and small scale Kelvin waves is the Kelvin wave frontogenesis theory developed by [4] and [5]. In fact, as the Kelvin wave is non-dispersive, its nonlinear dynamics is governed by the well known Burger's like equation, which allows wave breaking and shock formation in a finite time. Here, we extend the nonlinear Kelvin wave theory mentioned above to include its nonlinear coupling with short-wavelength eastward propagating Yanai modes and argue that this nonlinear coupling might explain the strong spectral peak band in intermediate to short scale eastward propagating Yanai modes found in observational studies. 
[1] MATSUNO,  T., 1966: Quasi-geostrophic motions in the equatorial area. J. Meteor. Soc. Japan, 44, 25-43.
[2] KILADIS, G. N.; WHEELER, M. C.; HAERTEL, P. T.; STRAUB, K. H.; ROUNDY, P. E., 2009:  Convectively coupled equatorial waves. Rev. Geophys., 47 (RG2003). 
[3] GILL, A..E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. R. Met. Soc.,106, 447-462.
[4] RIPA, P., 1982:  Nonlinear wave-wave interactions in a One-Layer Reduced-Gravity Model on the equatorial -plane. J. Phys. Oceanogr., 12, 97-111.
[5] BOYD, J. P., 1980: The nonlinear equatorial Kelvin wave. J. Phys. Oceanogr., 10, 1-11.