An intercomparison of subgrid models for large‐eddy simulation of katabatic flows. (11th September 2013)

• Record Type: Journal Article
• Authors: Smith, Craig M.; Porté‐Agel, Fernando
• Is Part Of: Quarterly journal of the Royal Meteorological Society. Volume 140:Number 681(2014:Apr.)
• Page Start: 1294
• Page End: 1303
• Publication Date: 2013-09-11
• Subjects: Meteorology -- Periodicals; 551.5
• DOI: 10.1002/qj.2212
• Languages: English
• ISSNs: 0035-9009

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>We present an intercomparison of three subgrid‐scale (SGS) models for large‐eddy simulation (LES) of katabatic flows. The SGS closures we study include the Smagorinsky formulation, a scale‐invariant dynamic model, and a scale‐dependent dynamic model. Downslope fluxes of mass and buoyancy deficit are highly sensitive to SGS closure choice. Due to strong shear and strong stratification, the dynamic models show a reduction of the Smagorinsky coefficient near the surface relative to the Smagorinsky model. Furthermore, results from both scale‐dependent dynamic models suggest that the assumptions of scale invariance in the dynamic model are violated. We present a second set of experiments which focus on grid resolution requirements of eddy‐resolving simulations of drainage flows. Downslope buoyancy and mass flux predictions produced by the scale‐dependent dynamic model are more robust with respect to grid resolution and grid anisotropy than the scale‐invariant dynamic and Smagorinsky SGS models. Predictions of vertically integrated downvalley mass and buoyancy fluxes are more sensitive to vertical grid resolution than horizontal grid resolution.</p> </abstract>