scholarly journals Implementing a new formulation in WRF-LES for Buoyant Plume Simulations: bPlume-WRF-LES model

2021 ◽  
Author(s):  
Sudheer R Bhimireddy ◽  
Kiran Bhaganagar
Keyword(s):  
Boundary Layer ◽  
Ambient Air ◽  
Turnover Time ◽  
Wind Forcing ◽  
Atmospheric Conditions ◽  
Large Area ◽  
Convective Boundary ◽  
Production Term ◽  
New Formulation ◽  
Les Model

AbstractA new formulation - bPlume-WRF-LES model - was implemented within the Weather Research and Forecast (WRF) model to simulate the two-way coupling between the atmospheric boundary layer (ABL) and gas plume (denser and lighter) released into the atmosphere. The existing WRF-large eddy simulation (WRF-LES) modeling system was modified by coupling an additional transport equation for the plume gas mixture and by accounting for the buoyant production term in the turbulence kinetic energy equation. The focus of the work was to understand the effect of atmospheric forcings on plume rise, plume mixing and plume dynamics during the early stages of plume development. For this purpose, the bPlume-WRF-LES model was used to simulate the release of buoyant plumes from a large area source into different atmospheric conditions with varying stratification and mean wind forcing values. Plumes released in a convective ABL background rise according to the 2/3 power law with time before reaching the boundary layer top and spreading laterally. The convective ABL eddy turnover time scale (t*) dictates the rate at which plume mixes with the ambient air inside the convective boundary layer (CBL) and the plume dilution rate scales as . Both the stratification and wind forcing enhance the plume mixing from the early plume development stage, and dilute the plume much faster. An increase in the mean winds within the CBL contributes to uniform mixing and greater bent-over plume behavior at a shorter downwind distance from the source.

The impact of large-scale winds on thermally driven flows and exchange processes over mountainous terrain

2020 ◽  
Author(s):  
Jan Weinkaemmerer ◽  
Ivan Bašták Ďurán ◽  
Jürg Schmidli
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Volume Effect ◽  
Turbulent Heat ◽  
Atmospheric Conditions ◽  
Free Atmosphere ◽  
Convective Boundary ◽  
Mean Values ◽  
Mountainous Regions ◽  
The Impact

<p>In the convective boundary layer over mountainous regions, the mean values and the fluxes of quantities like heat, mass, and momentum are strongly influenced by thermally induced flows. Several studies have pointed out that the enhanced warming of the air inside a valley can be explained by the valley-volume effect whereas the cross-valley circulation leads to a net export of heat to the free atmosphere. We are interested in the influence of an upper-level wind on the local circulations and the boundary-layer properties, both locally and in terms of the horizontal mean, as this aspect has not yet received much attention. LES are carried out over idealized, two-dimensional topographies using the CM1 numerical model. For the analysis, turbulent, mean-circulation, and large-scale contributions are systematically distinguished. Also, budget analyses are performed for the turbulence kinetic energy and the turbulent heat and mass flux. Based on the first results for periodic topographies, no crucial influence on the horizontally averaged heat-flux and temperature profile can be observed, even though the flow pattern of the thermal wind is qualitatively changed. In addition to that, the impact on moisture transport will be evaluated and simulations over different topographies as well as for different atmospheric conditions and surface properties will be presented.</p>

A New Mixing-Length Formulation for the Parameterization of Dry Convection: Implementation and Evaluation in a Mesoscale Model

2004 ◽  
Vol 132 (11) ◽  
pp. 2698-2707 ◽  
Author(s):  
J. Teixeira ◽  
J. P. Ferreira ◽  
P. M. A. Miranda ◽  
T. Haack ◽  
J. Doyle ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Large Scale ◽  
Mesoscale Model ◽  
Climate Impact ◽  
Layer Growth ◽  
Mixing Length ◽  
Convective Boundary ◽  
Realistic Representation ◽  
New Formulation

Abstract A realistic representation of the evolution of the dry convective boundary layer in mesoscale and large-scale atmospheric models has been an elusive goal for many years. In this paper the performance of a new mixing-length formulation for the dry convective boundary layer is evaluated in the context of the Coupled Ocean– Atmosphere Mesoscale Prediction System (COAMPS). In this new formulation, the mixing length is proportional to a time scale and to the square root of the turbulent kinetic energy. The model results are tested against observations from the Climate Impact of Changes in Land Use (CICLUS) field experiment in the south of Portugal. It is shown that COAMPS with the new formulation produces a more realistic simulation of the boundary layer growth. A data assimilation experiment performed with COAMPS shows that the improvements provided by the new formulation are significant, particularly in terms of the humidity vertical distribution. Finally, one-dimensional simulations are used to confirm that the new formulation provides more accurate results because of a more realistic representation of the entrainment and of the vertical mixing in general.

scholarly journals Local Convection and Turbulence in the Amazonia Using Large Eddy Simulation Model

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 399 ◽  
Author(s):  
Theomar Neves ◽  
Gilberto Fisch ◽  
Siegfried Raasch
Keyword(s):  
Boundary Layer ◽  
Sensible Heat Flux ◽  
Convective Boundary ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Forest Sites ◽  
Resolution Model ◽  
Turbulent Kinetic Energy Equation ◽  
High Resolution Model ◽  
Les Model

Using a high resolution model of Large Eddies Simulation (LES), named PALM from PArallel LES Model, a set of simulations were performed to understand how turbulence and convection behave in a pasture and forest sites in Amazonia during the dry and rainy seasons. Related to seasonality, dry period presented higher differences of values (40 W m−2) and patterns over the sites, while in the wet period have more similar characteristics (difference of −10 W m−2). The pasture site had more convection than the forest, with effective mixing and a deeper boundary layer (2600 m). The vertical decrease of sensible heat flux with altitude fed convection and also influenced the convective boundary layer (CBL) height. Regarding the components of turbulent kinetic energy equation, the thermal production was the most important component and the dissipation rate responded with higher growth, especially in cases of greatest mechanical production at the forest surface reaching values up to −20.0.

A New Moist Turbulence Parameterization in the Community Atmosphere Model

2009 ◽  
Vol 22 (12) ◽  
pp. 3422-3448 ◽  
Author(s):  
Christopher S. Bretherton ◽  
Sungsu Park
Keyword(s):  
Boundary Layer ◽  
Climate Models ◽  
Global Climate ◽  
Companion Paper ◽  
Cumulus Parameterization ◽  
Convective Boundary ◽  
Turbulence Parameterization ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
New Formulation

Abstract A new moist turbulence parameterization is presented and implemented in the Community Atmosphere Model (CAM). It is derived from Grenier and Bretherton but has been heavily modified to improve its numerical stability and efficiency with the long time steps used in climate models. A goal was to provide a more physically realistic treatment of marine stratocumulus-topped boundary layers than in the current CAM. Key features of the scheme include use of moist-conserved variables, an explicit entrainment closure for convective layers, diagnosis of turbulent kinetic energy (TKE) for computation of turbulent diffusivities, an efficient new formulation of TKE transport as a relaxation to layer-mean TKE, and unified treatment of all turbulent layers in each atmospheric column. The scheme is compared with the default turbulence parameterizations in the CAM using three single-column modeling cases, using both operational and high vertical and time resolution. Both schemes performed comparably well on the dry convective boundary layer case. For a stable boundary layer case, the default CAM overdeepens the boundary layer unless its free-tropospheric mixing length is greatly reduced, whereupon the new scheme and default CAM again both perform well at both tested resolutions. A nocturnal stratocumulus case was much better simulated by the new scheme than the default CAM, with much less resolution sensitivity. Global climate simulations with the new scheme in tandem with a new shallow cumulus parameterization are presented in a companion paper.

scholarly journals Erosion of the nocturnal boundary layer in the central Amazon during the dry season

2020 ◽  
Vol 50 (1) ◽  
pp. 80-89 ◽  
Author(s):  
Rayonil Gomes CARNEIRO ◽  
Gilberto FISCH ◽  
Camilla Kassar BORGES ◽  
Alice HENKES
Keyword(s):  
Boundary Layer ◽  
Microwave Radiometer ◽  
Sensible Heat Flux ◽  
Nocturnal Boundary Layer ◽  
Dry Season ◽  
Convective Boundary ◽  
Central Amazon ◽  
Resolution Model ◽  
Using Data ◽  
Les Model

ABSTRACT In this study, the erosion of the nocturnal boundary layer (NBL) was analyzed in the central Amazon during the dry season of 2014, using data from the GoAmazon 2014/5 Project and high-resolution model outputs (PArallelized Les Model - PALM). The dataset consisted of in situ (radiosonde) and remote sensing instruments measurements (Ceilometer, Lidar, Wind Profiler, microwave radiometer, and SODAR). The results showed that the NBL erosion occurred, on average, two hours after sunrise (06:00 local time), and the sensible heat flux provided more than 50% of the sensible heating necessary for the erosion process to occur. After the erosion, the convective phase developed quickly (175.2 m h-1). The measurements of the remote sensors showed that the Ceilometer, in general, presented satisfactory results in relation to the radiosondes for measuring the height of the planetary boundary layer. The PALM simulations represented well the NBL erosion, with a small underestimation (≈ 20 m) at the beginning of this phase. In the final phase of NBL erosion and in the initial stage of the development of the convective boundary layer (CBL), the model presented satisfactory results, with heights of CBL ranging from 800 m to 1,650 m, respectively.

scholarly journals An Approximate Footprint Model for Flux Measurements in the Convective Boundary Layer

2006 ◽  
Vol 23 (10) ◽  
pp. 1384-1394 ◽  
Author(s):  
Weiguo Wang ◽  
Kenneth J. Davis ◽  
Daniel M. Ricciuto ◽  
Martha P. Butler
Keyword(s):  
Boundary Layer ◽  
Stochastic Model ◽  
Convective Boundary Layer ◽  
Vertical Direction ◽  
Atmospheric Conditions ◽  
Flux Footprint ◽  
Convective Boundary ◽  
Obukhov Length ◽  
Footprint Model ◽  
Flux Measurements

Abstract An explicit footprint model for flux measurements of passive scalars in the lower part of the convective boundary layer (CBL) is introduced. A simple footprint model is derived analytically in an idealized CBL. The simple model can simulate the overall characteristics of the flux footprint. Then a method is proposed to adjust the analytical solutions to those from a Lagrangian stochastic model that considers more realistic atmospheric conditions in the vertical direction. The adjusted footprint model is a function of Monin–Obukhov length (L), roughness length, receptor height, and CBL depth (h). Comparison between the results from the adjusted footprint model and stochastic model suggests that the adjusted footprint model can well simulate the streamwise extent of the footprint within the dimensionless upwind distance X < 1, which accounts for a majority of the footprint. The model applies to stabilities of –L/h between 0.01 and 0.1 and roughness lengths between 10−5 and 2 × 10−3h in the lower part of the mixed layer (from 0.1h to 0.6h).

scholarly journals Vertical Velocity and Buoyancy Characteristics of Coherent Echo Plumes in the Convective Boundary Layer, Detected by a Profiling Airborne Radar

2006 ◽  
Vol 45 (6) ◽  
pp. 838-855 ◽  
Author(s):  
Qun Miao ◽  
Bart Geerts ◽  
Margaret LeMone
Keyword(s):  
Boundary Layer ◽  
Great Plains ◽  
Convective Boundary Layer ◽  
Ambient Air ◽  
Doppler Velocity ◽  
Convective Boundary ◽  
Millimeter Wave Radar ◽  
Radar Echoes ◽  
Temperature Excess ◽  
Wave Radar

Abstract Aircraft and airborne millimeter-wave radar observations are used to interpret the dynamics of radar echoes and radar-inferred updrafts within the well-developed, weakly sheared continental convective boundary layer. Vertically pointing radar reflectivity and Doppler velocity data collected above and below the aircraft, flying along fixed tracks in the central Great Plains during the International H2O Project (IHOP_2002), are used to define echo plumes and updraft plumes, respectively. Updraft plumes are generally narrower than echo plumes, but both types of plumes have the dynamical properties of buoyant eddies, especially at low levels. This buoyancy is driven both by temperature excess and water vapor excess over the ambient air. Plumes that are better defined in terms of reflectivity or updraft strength tend to be more buoyant.

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