Large-Eddy Simulation of Stratified Turbulence. Part II: Application of the Stretched-Vortex Model to the Atmospheric Boundary Layer

Matheou, Georgios; Chung, Daniel

doi:10.1175/jas-d-13-0306.1

Cited by 86 publications

(103 citation statements)

References 82 publications

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“…First, four different cooling rates are applied at the surface 1 that increase the overall level of stratification in the SBL compared to GABLS1 and, second, three levels of 1 Huang and Bou-Zeid (2013) Beare et al (2006) and Beare and Macvean (2004) used finest resolution meshes with spacing D 5 (1, 2) m, respectively, Huang and Bou-Zeid (2013) use a fine mesh (Dx, Dy, Dz) 5 (5:0, 5:0, 2:5) m, and Matheou and Chung (2014) also use D 5 2 m. Thus the finer spatial resolution and the grid mesh variation of more than 5 times in each coordinate direction used in the present simulations is a clear advance over past work.…”

Section: Design Of Les Experimentsmentioning

confidence: 99%

Turbulent Winds and Temperature Fronts in Large-Eddy Simulations of the Stable Atmospheric Boundary Layer

Sullivan

Weil

Patton

et al. 2016

Journal of the Atmospheric Sciences

120

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The nighttime high-latitude stably stratified atmospheric boundary layer (SBL) is computationally simulated using high-Reynolds number large-eddy simulation on meshes varying from 200 3 to 1024 3 over 9 physical hours for surface cooling rates C r 5 [0.25, 1] K h 21 . Continuous weakly stratified turbulence is maintained for this range of cooling, and the SBL splits into two regions depending on the location of the lowlevel jet (LLJ) and C r . Above the LLJ, turbulence is very weak and the gradient Richardson number is nearly constant: Ri ; 0:25. Below the LLJ, small scales are dynamically important as the shear and buoyancy frequencies vary with mesh resolution. The heights of the SBL and Ri noticeably decrease as the mesh is varied from 200 3 to 1024 3 . Vertical profiles of the Ozmidov scale L o show its rapid decrease with increasing C r , with L o , 2 m over a large fraction of the SBL for high cooling. Flow visualization identifies ubiquitous warm-cool temperature fronts populating the SBL. The fronts span a large vertical extent, tilt forward more so as the surface cooling increases, and propagate coherently. In a height-time reference frame, an instantaneous vertical profile of temperature appears intermittent, exhibiting a staircase pattern with increasing distance from the surface. Observations from CASES-99 also display these features. Conditional sampling based on linear stochastic estimation is used to identify coherent structures. Vortical structures are found upstream and downstream of a temperature front, similar to those in neutrally stratified boundary layers, and their dynamics are central to the front formation.

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Section: Design Of Les Experimentsmentioning

confidence: 99%

Turbulent Winds and Temperature Fronts in Large-Eddy Simulations of the Stable Atmospheric Boundary Layer

Sullivan

Weil

Patton

et al. 2016

Journal of the Atmospheric Sciences

120

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“…Their results indicate sensitivity to both horizontal and vertical grid spacing, as well as to the way surface fluxes and longwave radiation is modeled. While the studies mentioned above use anisotropic gridboxes, Matheou and Chung [] simulate the RF01 DYCOMS‐II case using the so‐called buoyancy‐adjusted stretched‐vortex SGS model [ Chung and Matheou , ] and isotropic gridboxes; they find that decreasing the grid spacing in all three directions from 10 to 2.5 m leads to higher cloud cover and LWP.…”

Section: Introductionmentioning

confidence: 99%

“…We note that these tendencies are observed in multiple studies, including most of those mentioned here, with the results of Stevens et al . [] and Matheou and Chung [] indicating stronger sensitivity to changes in the vertical grid spacing than to changes in the horizontal directions. The lack of sensitivity to horizontal resolution reported by Stevens et al .…”

Section: Introductionmentioning

confidence: 99%

Resolution and domain‐size sensitivity in implicit large‐eddy simulation of the stratocumulus‐topped boundary layer

Pedersen

Malinowski

Grabowski

2016

J Adv Model Earth Syst

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As a complement to measurements, numerical modeling facilitates improved understanding of the complex turbulent processes in the stratocumulus-topped boundary layer (STBL). Due to limited computational resources simulations are often run at too coarse resolutions to resolve details of cloud-top turbulence and potentially in computational domains too small to account for the largest scales of boundary layer circulations. The effects of such deficiencies are not fully understood. Here the influence of resolution/ anisotropy of the computational grid and domain size in under-resolved implicit large-eddy simulation of the STBL is investigated. The performed simulations are based on data from the first research flight of the DYCOMS-II campaign. Regarding cloud cover and domain-averaged liquid water path, simulations with horizontal/vertical grid spacing of 35/5 m, 70/10 m, and 105/15 m are found to agree better with measurements than more computationally expensive simulations with isotropic grid boxes, e.g., with 10/10 m or 15/15 m grid spacing. While decreasing the vertical grid spacing allows more representative simulation of the thin, turbulent, stably stratified interfacial layer between the STBL and the free troposphere, coarsening the horizontal resolution dampens vertical velocity fluctuations in this region and mimics the observed anisotropy of stably stratified small-scale turbulence near the cloud top. The size of the computational domain is found to have almost no impact on mean cloud properties. However, increasing it from 3:533:5 km 2 to 14314 km 2 does lead to the occurrence of larger coherent updraft structures. Increasing it further to 21321 km 2 shows little or no increase in the updraft size.

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“…The LES model and the case details are described in Ref. [4].The images correspond to a snapshot from the LES and show the complex multiscale structure of turbulence in the atmospheric boundary layer. The panels show horizontal (Fig.…”

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confidence: 99%

Large-eddy simulation of a stratocumulus cloud

2017

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Stratocumulus clouds form near the surface, covering about 20% of the Earth's surface, and typically appear as a lumpy cloud layer. Stratocumulus have a large effect on the Earth's energy balance because they strongly reflect incoming solar radiation. Climate projections are sensitive to the amount of cloud cover and small variations in the stratocumulus area coverage can produce energy-balance changes comparable to those due to greenhouse gases [1].Large-eddy simulation (LES) can be used to gain insight into the cloud physics and the factors controlling the cloud amount. LES is challenging, requiring very fine grid resolutions because of the sharp inversion (temperature increase) at the cloud top and the fine-scale forcing of buoyant convection that drives the turbulent flow. Turbulence is mainly generated by shear near the surface, (positively) buoyant plumes rising from the surface, and (negatively) buoyant fluid created near the cloud top by radiative cooling.The simulation corresponds to the conditions of the DYCOMS II campaign [2]. The computational domain is 5.12 2 × 1.5 km in the horizontal and vertical directions, and the grid resolution is 1.25 m with 4096 2 × 1200 grid points. The simulation utilizes the buoyancy adjusted stretched-vortex subgrid scale (SGS) model [3]. The LES model and the case details are described in Ref. [4].The images correspond to a snapshot from the LES and show the complex multiscale structure of turbulence in the atmospheric boundary layer. The panels show horizontal (Fig. 1) and vertical ( Fig. 2) cross sections of total water mixing ratio [q t = (mass of water vapor + liquid)/mass of dry atmosphere]. The total water mixing ratio is an active scalar and the main component of buoyancy. Near the surface, shear dominates the turbulence structure with streaks aligned with the mean wind direction. Higher up in the subcloud layer turbulence transitions to the cellularlike structure that is *

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Large-Eddy Simulation of Stratified Turbulence. Part II: Application of the Stretched-Vortex Model to the Atmospheric Boundary Layer

Cited by 86 publications

References 82 publications

Turbulent Winds and Temperature Fronts in Large-Eddy Simulations of the Stable Atmospheric Boundary Layer

Turbulent Winds and Temperature Fronts in Large-Eddy Simulations of the Stable Atmospheric Boundary Layer

Resolution and domain‐size sensitivity in implicit large‐eddy simulation of the stratocumulus‐topped boundary layer

Large-eddy simulation of a stratocumulus cloud

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