Revisiting entrainment relationships for shear-free and sheared convective boundary layers through large-eddy simulations

2018 ◽  
Vol 144 (716) ◽  
pp. 2182-2195 ◽  
Author(s):  
Cheng Liu ◽  
Evgeni Fedorovich ◽  
Jianping Huang
Keyword(s):  
Boundary Layers ◽  
Large Eddy Simulations ◽  
Convective Boundary ◽  
Large Eddy ◽  
Convective Boundary Layers

Representing Sheared Convective Boundary Layer by Zeroth- and First-Order-Jump Mixed-Layer Models: Large-Eddy Simulation Verification

2006 ◽  
Vol 45 (9) ◽  
pp. 1224-1243 ◽  
Author(s):  
David Pino ◽  
Jordi Vilà-Guerau de Arellano ◽  
Si-Wan Kim
Keyword(s):  
Large Eddy Simulation ◽  
Boundary Layers ◽  
Mixed Layer ◽  
Convective Boundary ◽  
First Order ◽  
Eddy Simulation ◽  
Jump Model ◽  
Large Eddy ◽  
Entrainment Zone ◽  
Convective Boundary Layers

Abstract Dry convective boundary layers characterized by a significant wind shear on the surface and at the inversion are studied by means of the mixed-layer theory. Two different representations of the entrainment zone, each of which has a different closure of the entrainment heat flux, are considered. The simpler of the two is based on a sharp discontinuity at the inversion (zeroth-order jump), whereas the second one prescribes a finite depth of the inversion zone (first-order jump). Large-eddy simulation data are used to provide the initial conditions for the mixed-layer models, and to verify their results. Two different atmospheric boundary layers with different stratification in the free atmosphere are analyzed. It is shown that, despite the simplicity of the zeroth-order-jump model, it provides similar results to the first-order-jump model and can reproduce the evolution of the mixed-layer variables obtained by the large-eddy simulations in sheared convective boundary layers. The mixed-layer model with both closures compares better with the large-eddy simulation results in the atmospheric boundary layer characterized by a moderate wind shear and a weak temperature inversion. These results can be used to represent the flux of momentum, heat, and other scalars at the entrainment zone in general circulation or chemistry transport models.

scholarly journals Analysis of Resolved and Parameterized Vertical Transports in Convective Boundary Layers at Gray-Zone Resolutions

2013 ◽  
Vol 70 (10) ◽  
pp. 3248-3261 ◽  
Author(s):  
Hyeyum Hailey Shin ◽  
Song-You Hong
Keyword(s):  
Boundary Layers ◽  
Numerical Models ◽  
Potential Temperature ◽  
Grid Size ◽  
Gray Zone ◽  
Subgrid Scale ◽  
Convective Boundary ◽  
Bottom Up ◽  
Large Eddy ◽  
Convective Boundary Layers

Abstract The gray zone of a physical process in numerical models is defined as the range of model resolution in which the process is partly resolved by model dynamics and partly parameterized. In this study, the authors examine the grid-size dependencies of resolved and parameterized vertical transports in convective boundary layers (CBLs) for horizontal grid scales including the gray zone. To assess how stability alters the dependencies on grid size, four CBLs with different surface heating and geostrophic winds are considered. For this purpose, reference data for grid-scale (GS) and subgrid-scale (SGS) fields are constructed for 50–4000-m mesh sizes by filtering 25-m large-eddy simulation (LES) data. As relative importance of shear increases, the ratio of resolved turbulent kinetic energy increases for a given grid spacing. Vertical transports of potential temperature, momentum, and a bottom-up diffusion passive scalar behave in a similar fashion. The effects of stability are related to the horizontal scale of coherent large-eddy structures that change in the different stability. The subgrid-scale vertical transport of heat and the bottom-up scalar are divided into a nonlocal mixing owing to the coherent structures and remaining local mixing. The separate treatment of the nonlocal and local transports shows that the grid-size dependency of the SGS nonlocal flux and its sensitivity to stability predominantly determine the dependency of total (nonlocal plus local) SGS transport.

Sign in / Sign up

Export Citation Format

Share Document