A Moist PBL Parameterization for Large-Scale Models and Its Application to Subtropical Cloud-Topped Marine Boundary Layers

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Abstract
A new general purpose boundary layer parameterization that permits realistic treatment of stratocumulus-capped boundary layers (SCBLs) with coarse vertical resolution is described. It combines a 1.5-order turbulent closure model with an entrainment closure at the boundary layer top. Three different implementations of the entrainment closure, in which the boundary layer height is respectively prognosed, reconstructed from thermodynamic values at the grid points, or restricted to lie on a flux level of the host model grid, are tested in a single-column modeling framework at both fine and coarse vertical resolution. The first two approaches permit a stratocumulus top and base to lie between grid levels and evolve continuously with time, but are more complicated to implement in a three-dimensional model. The model performs very well in cases of dry convection, whatever the inversion implementation and the vertical resolution. With 15-mb or better vertical resolution, all approaches properly simulate ... Abstract A new general purpose boundary layer parameterization that permits realistic treatment of stratocumulus-capped boundary layers (SCBLs) with coarse vertical resolution is described. It combines a 1.5-order turbulent closure model with an entrainment closure at the boundary layer top. Three different implementations of the entrainment closure, in which the boundary layer height is respectively prognosed, reconstructed from thermodynamic values at the grid points, or restricted to lie on a flux level of the host model grid, are tested in a single-column modeling framework at both fine and coarse vertical resolution. The first two approaches permit a stratocumulus top and base to lie between grid levels and evolve continuously with time, but are more complicated to implement in a three-dimensional model. The model performs very well in cases of dry convection, whatever the inversion implementation and the vertical resolution. With 15-mb or better vertical resolution, all approaches properly simulate ...

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