engleski

Generalizing the local mixing length-scale for stable atmospheric boundary layers

Excessively diffusive and much-too-deep modeled stable ABL flow is remedied by using a new generalized „ zless“ mixing length-scale, Λ , including the vertical wind shear, S explicitly. This generalization of Λ is based on a simplified turbulent kinetic energy (TKE) eqn. yielding Λ ~ (TKE)1/2/|S|, almost regardless of other parameterization details. The proportionality depends on known model constants and a function of Ri and turbulent Prandtl number, Pr ; Λ approaches Ozmidov scale (determined by the turbulent dissipation and buoyancy frequency) in the limit Ri >> 1. Tests with mesoscale MIUU model and a calibrated 1D semi-analytic Prandtl model prove this generalization of Λ correct and useful.

ICAM; katabatic flow; modeling; parameterization; Prandtl; Richardson number; strongly stratified turbulence

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