Linear parameterization of large-scale eddy transports

A method for the parameterization of the large-scale meridional transports of heat and vorticity is proposed which rests entirely upon data and does not invoke theories of large-scale turbulence. This method is tested for the case of a two-dimensional (zonally averaged) quasi-geostrophic model (M2). The necessary data are gained from the three-dimensional Lorenz model (M3). The parameterization is a linear one and the coefficients of the parameterization are determined so that the results of M2 come as close as possible to the results of M3. It turns out that M2 simulates the behaviour of M3 with great accuracy as long as the heat forcing does not depend on time. Once we introduce a variation of the heating in a rough similarity to the annual variation of the solar heating, our parameterization scheme behaves less satisfactorily. It then exhibits about the same quality as parameterization methods based on the Austausch concept.