Dissipation of Wave Drag in the Atmospheric Boundary Layer

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  • 1 Department of Meteorology, Uppsala University, Uppsala, Sweden
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Abstract

A simple parameterization of turbulence in an analytical study of wave drag (WD) is used upon governing equations for linearized, parallel, adiabatic, dry Boussinesq flow. Besides the known dependencies of WD on vertical profiles of the mean wind and temperature and the shape of orographic disturbance, WD also depends on eddy diffusivity, which parameterizes turbulence. Since eddy diffusivity is present, WD is not constant with height but is continuously dissipated in the atmospheric boundary layer (ABL). This dissipation is sometimes not negligible because characteristic wavelengths associated with an ABL over small ridges are short enough (λx ∼ 1 km) to experience overall turbulence. Under certain conditions and when no critical level is encountered (although critical level might be approached asymptotically here), WD can be reduced for roughly 15%–20% of its surface value. Hence, it is revealed that dissipation of WD can support turbulence in the stable ABL.

Abstract

A simple parameterization of turbulence in an analytical study of wave drag (WD) is used upon governing equations for linearized, parallel, adiabatic, dry Boussinesq flow. Besides the known dependencies of WD on vertical profiles of the mean wind and temperature and the shape of orographic disturbance, WD also depends on eddy diffusivity, which parameterizes turbulence. Since eddy diffusivity is present, WD is not constant with height but is continuously dissipated in the atmospheric boundary layer (ABL). This dissipation is sometimes not negligible because characteristic wavelengths associated with an ABL over small ridges are short enough (λx ∼ 1 km) to experience overall turbulence. Under certain conditions and when no critical level is encountered (although critical level might be approached asymptotically here), WD can be reduced for roughly 15%–20% of its surface value. Hence, it is revealed that dissipation of WD can support turbulence in the stable ABL.

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