The IDEMIX Model: Parameterization of Internal Gravity Waves for Circulation Models of Ocean and Atmosphere

Abstract

The IDEMIX concept is an energetically consistent framework to describe wave effects in circulation models of ocean and atmosphere. It is based on the radiative transfer equation for an internal gravity wave field in physical and wavenumber space and was shown to be successful for ocean applications. An improved IDEMIX model for the ocean will be constructed and extended by a new high-frequency, high vertical wavenumber compartment, forcing by mesoscale eddy dissipation, anisotropic tidal forcing, and wave--mean flow interaction. It will be validated using observational and model estimates. A novel concept for gravity wave parameterization in atmospheric circulation models is developed. As for the ocean, the wave field is represented by the wave energy density in physical and wavenumber space, and its prognostic computation is performed by the radiative transfer equation. This new concept goes far beyond conventional gravity wave schemes which are based on the single-column approximation and, in particular, on the strong assumptions of a stationary mean flow and a stationary wave energy equation. The radiative transfer equation has---to our knowledge---never been considered in the atmospheric community as a framework for subgrid-scale parameterization. The proposed parameterization will, for the first time, (1) include all relevant sources continuously in space and time and (2) accommodate all gravity wave sources (orography, fronts, and convection) in a single parameterization framework. Moreover, the new scheme is formulated in a precisely energy-preserving fashion. The project will contribute to a transfer of knowledge from the oceanic community to the atmospheric community and vice versa. We give a brief description of the oceanic and atmospheric internal wave fields, the most important processes of generation and interactions, and the ingredients of the model IDEMIX.