Some Effects Of An Ekman Boundary-Layer Parameterization On Various Models Of Atmospheric Flow |
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| Authors: | William Blumen |
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| Institution: | (1) Program in Atmospheric and Oceanic Sciences, University of Colorado, Boulder, Colorado 80309, USA |
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| Abstract: | The traditional Ekman boundary-layer parameterization is introduced into the quasigeostrophic Eady baroclinic instability model and into the deformation flow model, to couple the planetary boundary layer with the inviscid interior flow aloft. An explicit time-dependent version of this parameterization 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 thedifferent constraints imposed by each model. Further, the zero potential vorticity condition constrains the evolution of the baroclinic geostrophic part of the flow, which leads to an unphysical flow response when the Ekman boundary-layer parameterization is employed with this unbalanced model. The barotropic 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 processis shown to have an insignificant effect on this spin-down process. |
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| Keywords: | Ekman boundary-layer parameterization Spin-down Time-dependent Ekman pumping Zero potential vorticity model |
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