Barotropic Equatorial Waves: The Nonuniformity of the Equatorial Beta-Plane

Abstract

Some equatorially trapped motions cannot be modeled by the equatorial beta-plane. Our proof is a counter-example: if the zonal wavenumber m is large, barotropic Rossby-Haurwitz waves decay with latitude outside a narrow band about the equator and can be approximated by Hermite functions. The rather subtle effects of spherical geometry which create thew barotropic equatorial waves have important implications for short zonal wavelength motion in the tropics.