The Zonally Averaged Transport Characteristics of the GFDL General Circulation/Transport Model

Abstract The GFDL general circulation/tracer model has been used to generate the transport coefficients required in two-dimensional (zonally averaged) transport formulations. This was done by assuming a flux-gradient relationship and then, given gradient and flux statistics from two independent (and contrived) model tracer experiments, to derive the coefficients by inversion of this relation. Given the mean meridional circulation from the GCM, the antisymmetric and symmetric parts of the coefficients tensor determine the advective and diffusive contributions to the net meridional transport in the model. The effective transport circulation thus defined differs substantially from the Lagrangian mean and residual circulations and is in fact a simpler representation of the model circulation than either of these. The diffusive component is coherently structured, comprising the following components: (i) Strong quasi-horizontal mixing (Dyy ∼ 1 × 106 m2 s−1) in the midlatitude lower troposphere, apparently associ...