Título
Free and forced Rossby normal modes in a rectangular gulf of arbitrary orientation
Autor
FEDERICO GRAEF ZIEHL
Nivel de Acceso
Acceso Abierto
Referencia de datos
datasetDOI/10.1016/j.dynatmoce.2016.05.005
Materias
Resumen o descripción
A free Rossby normal mode in a rectangular gulf of arbitrary orientation is constructed by considering the reflection of a Rossby mode in a channel at the head of the gulf. Therefore, it is the superposition of four Rossby waves in an otherwise unbounded ocean with the same frequency and wavenumbers perpendicular to the gulf axis whose difference is equal to 2m!/W, where m is a positive integer and W the gulf’s width. The lower (or higher) modes with small m (or large m) are oscillatory (evanescent) in the coordinate along the
gulf;these are elucidated geometrically. However for oceanographically realistic parameter values, most of the modes are evanescent.
When the gulf is forced at the mouth with a single Fourier component, the response is in general an infinite sum of modes that are needed to match the value of the streamfunction at the gulf’s entrance. The dominant mode of the response is the resonant one, which corresponds to forcing with a frequency ω and wavenumber normalto the gulf axis # appropriate to a gulf mode: # =− ˇ sin˛/(2ω) ± M!/W, where ˛ is the angle between the gulf’s axis and the eastern direction (+ve clockwise) and M the resonant’s mode number. For zonal gulfs ω drops out of the resonance condition.
For the special cases # = 0 in which the free surface goes up and down atthe mouth with no flow through it, or a flow with a sinusoidal profile, resonant modes can get excited for very specific frequencies (only for non-zonal gulfs in the # = 0 case). The resonant mode is around the annual frequency for a wide range of gulf orientations ˛ ∈ [40◦, 130◦] or ˛ ∈ [220◦,310◦] and gulf widths between 150 and 200 km; these include the Gulf of California and the Adriatic Sea. If # is imaginary, i.e. a flow with an exponential profile, there is no resonance. In general less modes get excited if the gulf is zonally oriented.
Editor
Elsevier
Fecha de publicación
mayo de 2016
Tipo de publicación
Artículo
Versión de la publicación
Versión aceptada
Recurso de información
Formato
application/pdf
Fuente
Dynamics of Atmospheres and Oceans Vol. 75 , Págs. 46–57
Idioma
Inglés
Repositorio Orígen
Repositorio Institucional CICESE
Descargas
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