Equatorial Kelvin-like waves on slowly rotating and/or small-sized spheres: Application to Venus and Titan

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Equatorial Kelvin waves, which have been observed in planetary fluids, produce superrotation and climatological variability. Although the meridional flow component is zero on Earth's beta-plane in the absence of background basic flow, it cannot be neglected on spheres in some planetary fluids when the Lamb parameter is small. For a vertically propagating Kelvin-like wave in the absence of background wind shear, meridional flows produce equatorward heat transport, i.e., a downward Eliassen-Palm flux. The vertical momentum transport caused by the equatorward heat flux has a theoretical upper limit, and the normalized flux is analytically expressed as a simple function that is independent of the Lamb parameter. On a slowly rotating and/or small-sized planet, we need to consider the meridional flow component of the equatorial Kelvin-like wave and its related heat flux on the sphere, and further consider their modification owing to background flow shear through coupling with high-latitude Rossby waves.