Towards a seamlessly diagnosable expression for the energy flux associated with both equatorial and mid-latitude waves

Aiki, Hidenori, Greatbatch, Richard John and Claus, Martin (2017) Towards a seamlessly diagnosable expression for the energy flux associated with both equatorial and mid-latitude waves Progress in Earth and Planetary Science, 4 (1). Art. No. 11. DOI 10.1186/s40645-017-0121-1.

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Abstract

For mid-latitude Rossby waves (RWs) in the atmosphere, the expression for the energy flux for use in a model diagnosis, and without relying on a Fourier analysis or a ray theory, has previously been derived using quasi-geostrophic equations and is singular at the equator. By investigating the analytical solution of both equatorial and mid-latitude waves, the authors derive an exact universal expression for the energy flux which is able to indicate the direction of the group velocity at all latitudes for linear shallow water waves. This is achieved by introducing a streamfunction as given by the inversion equation of Ertel’s potential vorticity, a novel aspect for considering the energy flux. For ease of diagnosis from a model, an approximate version of the universal expression is explored and illustrated for a forced/dissipative equatorial basin mode simulated by a single-layer oceanic model that includes both mid-latitude RWs and equatorial waves. Equatorial Kelvin Waves (KWs) propagate eastward along the equator, are partially redirected poleward as coastal KWs at the eastern boundary of the basin, and then shed mid-latitude RWs that propagate westward into the basin interior. The connection of the equatorial and coastal waveguides has been successfully illustrated by the approximate expression of the group-velocity-based energy flux of the present study. This will allow for tropical-extratropical interactions in oceanic and atmospheric model outputs to be diagnosed in terms of an energy cycle in a future study.

Document Type: Article
Keywords: Group velocity; Model diagnosis; Equatorial Rossby waves; Equatorial mixed Rossby-gravity waves; Equatorial inertia-gravity waves; Equatorial Kelvin waves; Coastal Kelvin waves; Mid-latitude Rossby waves; Mid-latitude inertia-gravity waves; Tropical-extratropical interactions
Research affiliation: OceanRep > SFB 754 > A9
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > SFB 754
Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1186/s40645-017-0121-1
ISSN: 2197-4284
Projects: SFB754, SACUS, PREFACE
Date Deposited: 03 Apr 2017 08:13
Last Modified: 03 Apr 2017 09:12
URI: http://eprints.uni-kiel.de/id/eprint/37344

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