The Experts below are selected from a list of 6963 Experts worldwide ranked by ideXlab platform
Monica Moroni - One of the best experts on this subject based on the ideXlab platform.
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numerical study of the daytime planetary boundary layer over an idealized urban area influence of surface properties anthropogenic heat flux and Geostrophic Wind intensity
Journal of Applied Meteorology and Climatology, 2016Co-Authors: Serena Falasca, Franco Catalano, Monica MoroniAbstract:AbstractLarge-eddy simulations of an idealized diurnal urban heat island are performed using the Weather Research and Forecasting Model. The surface energy balance over an inhomogeneous terrain is solved considering the anthropogenic heat contribution and the differences of thermal and mechanical properties between urban and rural surfaces. Several cases are simulated together with a reference case, considering different values of the control parameters: albedo, thermal inertia, roughness length, anthropogenic heat emission, and Geostrophic Wind intensity. Spatial distributions of second-moment statistics, including the turbulent kinetic energy (TKE) budget, are analyzed to characterize the structure of the planetary boundary layer (PBL). The effect of each control parameter value on the turbulent properties of the PBL is investigated with respect to the reference case. For all of the analyzed cases, the primary source of TKE is the buoyancy in the lower half of the PBL, the shear in the upper half, and t...
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numerical study of the daytime planetary boundary layer over an idealized urban area influence of surface properties anthropogenic heat flux and Geostrophic Wind intensity
Journal of Applied Meteorology and Climatology, 2016Co-Authors: Serena Falasca, Franco Catalano, Monica MoroniAbstract:AbstractLarge-eddy simulations of an idealized diurnal urban heat island are performed using the Weather Research and Forecasting Model. The surface energy balance over an inhomogeneous terrain is solved considering the anthropogenic heat contribution and the differences of thermal and mechanical properties between urban and rural surfaces. Several cases are simulated together with a reference case, considering different values of the control parameters: albedo, thermal inertia, roughness length, anthropogenic heat emission, and Geostrophic Wind intensity. Spatial distributions of second-moment statistics, including the turbulent kinetic energy (TKE) budget, are analyzed to characterize the structure of the planetary boundary layer (PBL). The effect of each control parameter value on the turbulent properties of the PBL is investigated with respect to the reference case. For all of the analyzed cases, the primary source of TKE is the buoyancy in the lower half of the PBL, the shear in the upper half, and t...
Franco Catalano - One of the best experts on this subject based on the ideXlab platform.
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numerical study of the daytime planetary boundary layer over an idealized urban area influence of surface properties anthropogenic heat flux and Geostrophic Wind intensity
Journal of Applied Meteorology and Climatology, 2016Co-Authors: Serena Falasca, Franco Catalano, Monica MoroniAbstract:AbstractLarge-eddy simulations of an idealized diurnal urban heat island are performed using the Weather Research and Forecasting Model. The surface energy balance over an inhomogeneous terrain is solved considering the anthropogenic heat contribution and the differences of thermal and mechanical properties between urban and rural surfaces. Several cases are simulated together with a reference case, considering different values of the control parameters: albedo, thermal inertia, roughness length, anthropogenic heat emission, and Geostrophic Wind intensity. Spatial distributions of second-moment statistics, including the turbulent kinetic energy (TKE) budget, are analyzed to characterize the structure of the planetary boundary layer (PBL). The effect of each control parameter value on the turbulent properties of the PBL is investigated with respect to the reference case. For all of the analyzed cases, the primary source of TKE is the buoyancy in the lower half of the PBL, the shear in the upper half, and t...
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numerical study of the daytime planetary boundary layer over an idealized urban area influence of surface properties anthropogenic heat flux and Geostrophic Wind intensity
Journal of Applied Meteorology and Climatology, 2016Co-Authors: Serena Falasca, Franco Catalano, Monica MoroniAbstract:AbstractLarge-eddy simulations of an idealized diurnal urban heat island are performed using the Weather Research and Forecasting Model. The surface energy balance over an inhomogeneous terrain is solved considering the anthropogenic heat contribution and the differences of thermal and mechanical properties between urban and rural surfaces. Several cases are simulated together with a reference case, considering different values of the control parameters: albedo, thermal inertia, roughness length, anthropogenic heat emission, and Geostrophic Wind intensity. Spatial distributions of second-moment statistics, including the turbulent kinetic energy (TKE) budget, are analyzed to characterize the structure of the planetary boundary layer (PBL). The effect of each control parameter value on the turbulent properties of the PBL is investigated with respect to the reference case. For all of the analyzed cases, the primary source of TKE is the buoyancy in the lower half of the PBL, the shear in the upper half, and t...
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Large-Eddy Simulation of the Daytime Boundary Layer in an Idealized Valley Using the Weather Research and Forecasting Numerical Model
Boundary-Layer Meteorology, 2010Co-Authors: Franco Catalano, Chinhoh MoengAbstract:A three-dimensional numerical meteorological model is used to perform large-eddy simulations of the upslope flow circulation over a periodic ridge-valley terrain. The subgrid-scale quantities are modelled using a prognostic turbulence kinetic energy (TKE) scheme, with a grid that has a constant horizontal resolution of 50 m and is stretched along the vertical direction. To account for the grid anisotropy, a modified subgrid length scale is used. To allow for the response of the surface fluxes to the valley-flow circulation, the soil surface temperature is imposed and the surface heat and momentum fluxes are computed based on Monin–Obukhov similarity theory. The model is designed with a symmetrical geometry using periodic boundary conditions in both the x and y directions. Two cases are simulated to study the influence of along-valley Geostrophic Wind forcing with different intensities. The presence of the orography introduces numerous complexities both in the mean properties of the flow and in the turbulent features, even for the idealized symmetric geometry. Classical definitions for the height of the planetary boundary layer (PBL) are revisited and redefined to capture the complex structure of the boundary layer. Analysis of first- and second-moment statistics, along with TKE budget, highlights the different structure of the PBL at different regions of the domain.
Serena Falasca - One of the best experts on this subject based on the ideXlab platform.
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numerical study of the daytime planetary boundary layer over an idealized urban area influence of surface properties anthropogenic heat flux and Geostrophic Wind intensity
Journal of Applied Meteorology and Climatology, 2016Co-Authors: Serena Falasca, Franco Catalano, Monica MoroniAbstract:AbstractLarge-eddy simulations of an idealized diurnal urban heat island are performed using the Weather Research and Forecasting Model. The surface energy balance over an inhomogeneous terrain is solved considering the anthropogenic heat contribution and the differences of thermal and mechanical properties between urban and rural surfaces. Several cases are simulated together with a reference case, considering different values of the control parameters: albedo, thermal inertia, roughness length, anthropogenic heat emission, and Geostrophic Wind intensity. Spatial distributions of second-moment statistics, including the turbulent kinetic energy (TKE) budget, are analyzed to characterize the structure of the planetary boundary layer (PBL). The effect of each control parameter value on the turbulent properties of the PBL is investigated with respect to the reference case. For all of the analyzed cases, the primary source of TKE is the buoyancy in the lower half of the PBL, the shear in the upper half, and t...
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numerical study of the daytime planetary boundary layer over an idealized urban area influence of surface properties anthropogenic heat flux and Geostrophic Wind intensity
Journal of Applied Meteorology and Climatology, 2016Co-Authors: Serena Falasca, Franco Catalano, Monica MoroniAbstract:AbstractLarge-eddy simulations of an idealized diurnal urban heat island are performed using the Weather Research and Forecasting Model. The surface energy balance over an inhomogeneous terrain is solved considering the anthropogenic heat contribution and the differences of thermal and mechanical properties between urban and rural surfaces. Several cases are simulated together with a reference case, considering different values of the control parameters: albedo, thermal inertia, roughness length, anthropogenic heat emission, and Geostrophic Wind intensity. Spatial distributions of second-moment statistics, including the turbulent kinetic energy (TKE) budget, are analyzed to characterize the structure of the planetary boundary layer (PBL). The effect of each control parameter value on the turbulent properties of the PBL is investigated with respect to the reference case. For all of the analyzed cases, the primary source of TKE is the buoyancy in the lower half of the PBL, the shear in the upper half, and t...
Rachel Honnert - One of the best experts on this subject based on the ideXlab platform.
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grey zone turbulence in the neutral atmospheric boundary layer
Boundary-Layer Meteorology, 2019Co-Authors: Rachel HonnertAbstract:The turbulence generated by Wind shear is described at grey-zone resolutions using a theoretical neutral boundary layer based on atmospheric conditions constructed from measurements from the CASES-99 field campaign. Six-metre-resolution large-eddy simulations (LES) are performed to access the “true” resolved turbulence for two cases, corresponding to a forcing of the boundary layer by zonal Geostrophic Wind speeds of $$10\,\text {m}\,\text {s}^{-1}$$ and $$20\,\text {m}\,\text {s}^{-1}$$ . The LES fields are subject to a coarse-graining procedure in order to compute turbulence diagnostics in the grey zone, with the robustness and weakness of various averaging procedures tested, for which simple top-hat averaging is found to be both suitable and accurate. In addition, the “true” resolved and subgrid-scale fluxes, variances, turbulent kinetic energy and production terms are quantified on various scales. The grey zone of turbulence is defined as the range of scales where 10–90% of turbulence is resolved, which here ranges from resolutions of 25– $$800\,\hbox {m}$$ ( $$0.03<\Delta x/h<1$$ , where $$\Delta x$$ is the horizontal resolution, and h is the boundary-layer height). The subgrid/resolved partitioning of the variances of the velocity components depends on the Geostrophic Wind speed, which is not the case for the momentum-flux partitioning. Dynamic production terms show that fine-scale turbulence is isotropic ( $$\Delta x/h<0.03$$ ) and is quasi one-directional, oriented in the direction of the Geostrophic Wind vector at the mesoscale ( $$\Delta x/h>1$$ ). The turbulence parametrizations, which are tested in the Meso-NH model by running simulations at resolutions from the LES scale to the mesoscale, fail to produce the correct turbulence regardless of resolution.
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grey zone turbulence in the neutral atmospheric boundary layer
Boundary-Layer Meteorology, 2019Co-Authors: Rachel HonnertAbstract:The turbulence generated by Wind shear is described at grey-zone resolutions using a theoretical neutral boundary layer based on atmospheric conditions constructed from measurements from the CASES-99 field campaign. Six-metre-resolution large-eddy simulations (LES) are performed to access the “true” resolved turbulence for two cases, corresponding to a forcing of the boundary layer by zonal Geostrophic Wind speeds of \(10\,\text {m}\,\text {s}^{-1}\) and \(20\,\text {m}\,\text {s}^{-1}\). The LES fields are subject to a coarse-graining procedure in order to compute turbulence diagnostics in the grey zone, with the robustness and weakness of various averaging procedures tested, for which simple top-hat averaging is found to be both suitable and accurate. In addition, the “true” resolved and subgrid-scale fluxes, variances, turbulent kinetic energy and production terms are quantified on various scales. The grey zone of turbulence is defined as the range of scales where 10–90% of turbulence is resolved, which here ranges from resolutions of 25–\(800\,\hbox {m}\) (\(0.03 1\)). The turbulence parametrizations, which are tested in the Meso-NH model by running simulations at resolutions from the LES scale to the mesoscale, fail to produce the correct turbulence regardless of resolution.
Chinhoh Moeng - One of the best experts on this subject based on the ideXlab platform.
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Large-Eddy Simulation of the Daytime Boundary Layer in an Idealized Valley Using the Weather Research and Forecasting Numerical Model
Boundary-Layer Meteorology, 2010Co-Authors: Franco Catalano, Chinhoh MoengAbstract:A three-dimensional numerical meteorological model is used to perform large-eddy simulations of the upslope flow circulation over a periodic ridge-valley terrain. The subgrid-scale quantities are modelled using a prognostic turbulence kinetic energy (TKE) scheme, with a grid that has a constant horizontal resolution of 50 m and is stretched along the vertical direction. To account for the grid anisotropy, a modified subgrid length scale is used. To allow for the response of the surface fluxes to the valley-flow circulation, the soil surface temperature is imposed and the surface heat and momentum fluxes are computed based on Monin–Obukhov similarity theory. The model is designed with a symmetrical geometry using periodic boundary conditions in both the x and y directions. Two cases are simulated to study the influence of along-valley Geostrophic Wind forcing with different intensities. The presence of the orography introduces numerous complexities both in the mean properties of the flow and in the turbulent features, even for the idealized symmetric geometry. Classical definitions for the height of the planetary boundary layer (PBL) are revisited and redefined to capture the complex structure of the boundary layer. Analysis of first- and second-moment statistics, along with TKE budget, highlights the different structure of the PBL at different regions of the domain.
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entrainment processes in the convective boundary layer with varying Wind shear
Boundary-Layer Meteorology, 2003Co-Authors: S W Kim, Soonugn Park, Chinhoh MoengAbstract:Large-eddy simulations (LES) are performed to investigate the entrainment andthe structure of the inversion layer of the convective boundary layer (CBL) withvarying Wind shears. Three CBLs are generated with the constant surface kinematicheat flux of 0.05 K m s-1 and varying Geostrophic Wind speeds from 5 to 15m s-1. Heat flux profiles show that the maximum entrainment heat flux as afraction of the surface heat flux increases from 0.13 to 0.30 in magnitude withincreasing Wind shear. The thickness of the entrainment layer, relative to the depthof the well-mixed layer, increases substantially from 0.36 to 0.73 with increasingWind shear. The identification of vortices and extensive flow visualizations nearthe entrainment layer show that concentrated vortices perpendicular to the meanboundary-layer Wind direction are identified in the capping inversion layer for thecase of strong Wind shear. These vortices are found to develop along the mean Winddirections over strong updrafts, which are generated by convective rolls and to appearas large-scale wavy motions similar to billows generated by the Kelvin–Helmholtzinstability. Quadrant analysis of the heat flux shows that in the case of strong Windshear, large fluctuations of temperature and vertical velocity generated by largeamplitude wavy motions result in greater heat flux at each quadrant than that inthe weak Wind shear case.