Interaction of equatorially trapped waves and a background shear: numerical and theoretical issues.
Date
2011-01-19T20:01:48Z
Authors
Namazi, Maryam
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Abstract
The equatorial atmosphere harbours a large spectrum of waves that are trapped
near and travel along the equator. These equatorially trapped waves interact nonlinearly
with each other, with the extra-tropics and with the planetary-barotropic
waves. Here, we consider advected shallow water equations that represent interactions
of these equatorial waves, associated with the first baroclinic mode, with prescribed
meridional-barotropic shears. We present three well-known numerical schemes for
handling this system and discuss the risk of applying them crudely to equatorial
waves. We study the properties of these waves, such as their phase speed and their
trapping around the equator, using two approaches: linear analysis and the time evolutions
of the system derived by meridional projection of the barotropic-first baroclinic
system. We show that in the sheared environment the symmetric (anti-symmetric)
equatorial waves excite other symmetric (anti-symmetric) equatorial waves of the
same wavenumber and of different strengths.
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Keywords
Equatorially trapped waves, barotropic shear, Numerical schemes, Finite volumes, Galerkin projection, Wave shear-interactions