Some effects of an Ekman boundary-layer parameterization on various modelsof atmospheric flow

The traditional Ekman boundary-layer parameterization is introduced into th e quasigeostrophic Eady baroclinic instability model and into the deformati on flow model, to couple the planetary boundary layer with the inviscid int erior flow aloft. An explicit time-dependent version of this parameterizati on is then introduced into an unbalanced zero potential vorticity model to evaluate the initial transient response. It is noted that the adaptation of the geostrophic flow to the same parameterization is different in each of the balanced models. The characteristic flow response reflects the differen t constraints imposed by each model. Further, the zero potential vorticity condition constrains the evolution of the baroclinic geostrophic part of th e flow, which leads to an unphysical flow response when the Ekman boundary- layer parameterization is employed with this unbalanced model. The barotrop ic part of the flow does, however, evolve in a physically consistent manner spinning down to reflect the introduction of low momentum air pumped into the interior from the boundary layer. Moreover, the transient spin-up proce ss is shown to have an insignificant effect on this spin-down process.