Large Eddy Simulation of an Inhomogeneous Atmospheric Boundary Layer under Neutral Conditions

Lin, Ching‐Long; Glendening, John W.

doi:10.1175/1520-0469(2002)059<2479:lesoai>2.0.co;2

Cited by 20 publications

(13 citation statements)

References 35 publications

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“…These issues range from the basic theoretical applicability of Monin-Obukhov similarity theory (Khanna and Brasseur, 1997) to the role of land surface heterogeneity on boundary layer dynamics (Lin and Glendening, 2002) and 3404 N. A. Brunsell et al: Surface heterogeneity and boundary layer partitioning the role of surface roughness and blending heights (Bou-Zeid et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Brunsell

Mechem

Anderson³

2011

Atmos. Chem. Phys.

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Abstract. The role of land-atmosphere interactions under heterogeneous surface conditions is investigated in order to identify mechanisms responsible for altering surface heat and moisture fluxes. Twelve coupled land surface -large eddy simulation scenarios with four different length scales of surface variability under three different horizontal wind speeds are used in the analysis. The base case uses Landsat ETM imagery over the Cloud Land Surface Interaction Campaign (CLASIC) field site for 3 June 2007. Using wavelets, the surface fields are band-pass filtered in order to maintain the spatial mean and variances to length scales of 200 m, 1600 m, and 12.8 km as lower boundary conditions to the model (approximately 0.25, 1.2 and 9.5 times boundary layer height). The simulations exhibit little variation in net radiation. Rather, there is a pronounced change in the partitioning of the surface energy between sensible and latent heat flux. The sensible heat flux is dominant for intermediate surface length scales. For smaller and larger scales of surface heterogeneity, which can be viewed as being more homogeneous, the latent heat flux becomes increasingly important. The simulations showed approximately 50 Wm −2 difference in the spatially averaged latent heat flux. The results reflect a general decrease of the Bowen ratio as the surface conditions transition from heterogeneous to homogeneous. Air temperature is less sensitive to variations in surface heterogeneity than water vapor, which implies that the role of surface heterogeneity may be to maximize convective heat fluxes through modifying and maintaining local temperature gradients. More homogeneous surface conditions (i.e. smaller length scales), on the other hand, tend to maximize latent heat flux. The intermediate scale (1600 m) this does not hold, and is a more complicated interaction of scales.Correspondence to: N. A. Brunsell (brunsell@ku.edu) Scalar vertical profiles respond predictably to the partitioning of surface energy. Fourier spectra of the vertical wind speed, air temperature and specific humidity (w,T andq) and associated cospectra (wT ,wq andTq), however, are insensitive to the length scale of surface heterogeneity, but the near surface spectra are sensitive to the mean wind speed.

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Section: Introductionmentioning

confidence: 99%

Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Brunsell

Mechem

Anderson³

2011

Atmos. Chem. Phys.

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“…Li et al (1990) used a higher-order turbulence closure model to examine the momentum budget at a grassland-to-forest interface. Budgets of TKE, momentum and uw covariance downwind of a step increase of surface roughness were studied by Antonia and Luxton (1971) in a wind tunnel and by Lin and Glendening (2002) using a LES model. In these two studies, the rough surface was set at the same level as the smooth surface.…”

Section: Introductionmentioning

confidence: 99%

Large-eddy Simulation of Turbulent Flow across a Forest Edge. Part II: Momentum and Turbulent Kinetic Energy Budgets

Yang

Morse

Shaw

et al. 2006

Boundary-Layer Meteorol

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Momentum and turbulent kinetic energy (TKE) budgets across a forest edge have been investigated using large-eddy simulation (LES). Edge effects are observed in the rapid variation of a number of budget terms across this vegetation transition. The enhanced drag force at the forest edge is largely balanced by the pressure gradient force and by streamwise advection of upstream momentum, while vertical turbulent diffusion is relatively insignificant. For variance and TKE budgets, the most important processes at the forest edge are production due to the convergence (or divergence) of the mean flow, streamwise advection, pressure diffusion and enhanced dissipation by canopy drag. Turbulent diffusion, pressure redistribution and vertical shear production, which are characteristic processes in homogeneous canopy flow, are less important at the forest transition. We demonstrate that, in the equilibrated canopy flow, a substantial amount of TKE produced in the streamwise direction by the vertical shear of the mean flow is redistributed in the vertical direction by pressure fluctuations. This redistribution process occurs in the upper canopy layers. Part of the TKE in the vertical velocity component is transferred by turbulent and pressure diffusion to the lower canopy levels, where pressure redistribution takes place again and feeds TKE back to the streamwise direction. In this TKE cycle, the primary source terms are vertical shear production for streamwise velocity variance and pressure redistribution for vertical velocity variance. The evolution of these primary source terms downwind of the forest edge largely controls the adjustment rates of velocity variances.

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“…In addition, many LES studies using traditional SGS models have been performed using data collected from field studies over spatially distributed non-homogeneous surfaces with varying roughness or fluxes as lower boundary conditions (e.g. Hechtel et al 1990;Avissar and Schmidt 1998;Albertson and Parlange 1999a, b;Albertson et al 2001;Lin and Glendening 2002).…”

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confidence: 99%

Application of Dynamic Subgrid-scale Models for Large-eddy Simulation of the Daytime Convective Boundary Layer over Heterogeneous Surfaces

Huang

Stevens

Margulis

2007

Boundary-Layer Meteorol

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The sensitivity of large-eddy simulation (LES) to the representation of subgrid-scale (SGS) processes is explored for the case of the convective boundary layer (CBL) developing over surfaces with varying degrees of spatial heterogeneity. Three representations of SGS processes are explored: the traditional constant Smagorinsky-Lilly model and two other dynamic models with Lagrangian averaging approaches to calculate the Smagorinsky coefficient (C S ) and SGS Prandtl number (Pr). With initial data based roughly on the observed meteorology, simulations of daytime CBL growth are performed over surfaces with characteristics (i.e. fluxes and roughness) ranging from homogeneous, to striped heterogeneity, to a realistic representation of heterogeneity as derived from a recent field study. In both idealized tests and the realistic case, SGS sensitivities are mostly manifest near the surface and entrainment zone. However, unlike simulations over complex domains or under neutral or stable conditions, these differences for the CBL simulation, where large eddies dominate, are not significant enough to distinguish the performance of the different SGS models, irrespective of surface heterogeneity.

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Large Eddy Simulation of an Inhomogeneous Atmospheric Boundary Layer under Neutral Conditions

Cited by 20 publications

References 35 publications

Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Large-eddy Simulation of Turbulent Flow across a Forest Edge. Part II: Momentum and Turbulent Kinetic Energy Budgets

Application of Dynamic Subgrid-scale Models for Large-eddy Simulation of the Daytime Convective Boundary Layer over Heterogeneous Surfaces

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