A spectral coupled ocean-atmosphere model

Abstract

A spectral coupled ocean-atmosphere model, suitable for studying the El-Nino Southern Oscillation, has been formulated. The atmospheric component is global in its extent, while the oceanic part is a hemispheric basin representing the Pacific Ocean. Multi-decadal integrations of the model have been performed with realistic topography and seasonal variations in the atmospheric radiative forcing, and for resolutions ranging from low (rhomboidal wavenumber 15 (R15)) to intermediate (R31) to high (R60). El-Nino Southern Oscillations are produced with realistic frequency spectra, even at low resolution. The reason for this is the conserving properties of the spectral technique (in the inviscid case) and hence the model is stable with realistic and small dissipation while commonly used grid-point models require too large dissipation for stability.