A Model for Describing the Evolution of the Energy Density Spectrum in the Convective Boundary Layer Growth

2007 ◽  
pp. 692-694
Author(s):  
Antonio Goulart ◽  
Haroldo F. Campos Velho ◽  
Gervásio Annes Degrazia ◽  
Domenico Anfossi ◽  
Otávio Acevedo ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Energy Density ◽  
Convective Boundary Layer ◽  
Layer Growth ◽  
Convective Boundary ◽  
Density Spectrum ◽  
Boundary Layer Growth

A MATHEMATICAL MODEL FOR THE DECAYING ENERGY DENSITY SPECTRUM IN A CONVECTIVE BOUNDARY LAYER: ISOTROPIC CASE

2002 ◽  
Vol 4 (1-2) ◽  
pp. 6
Author(s):  
A. Goulart ◽  
Gervasio Annes Degrazia ◽  
Domenico Anfossi ◽  
Marco T. Vilhena ◽  
Claudia Rejane Jacondino de Campos
Keyword(s):  
Boundary Layer ◽  
Mathematical Model ◽  
Energy Density ◽  
Convective Boundary Layer ◽  
Isotropic Case ◽  
Convective Boundary ◽  
Density Spectrum

scholarly journals DIFFERENT PARAMETERIZATIONS FOR WIND VARIANCE APPLIED TO THE CONVECTIVE BOUNDARY LAYER GROWTH MODEL

2013 ◽  
Vol 0 (0) ◽  
Author(s):  
André Nunes ◽  
Prakki Satyamurty ◽  
Haroldo De Campos Velho ◽  
Maria Eugenia Welter
Keyword(s):  
Boundary Layer ◽  
Growth Model ◽  
Convective Boundary Layer ◽  
Layer Growth ◽  
Convective Boundary ◽  
Boundary Layer Growth

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 Some Observational Evidence for Dry Soils Supporting Enhanced Relative Humidity at the Convective Boundary Layer Top

2012 ◽  
Vol 13 (4) ◽  
pp. 1347-1358 ◽  
Author(s):  
D. Westra ◽  
G. J. Steeneveld ◽  
A. A. M. Holtslag
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Conceptual Framework ◽  
Convective Boundary Layer ◽  
Land Surface ◽  
Layer Growth ◽  
Observational Evidence ◽  
Cloud Formation ◽  
Semiarid Region ◽  
Convective Boundary

Abstract The tendency of the relative humidity at the top of a clear convective boundary layer (RHtop) is studied as an indicator of cloud formation over a semiarid region within the conceptual framework introduced by Ek and Holtslag. Typically the tendency of RHtop increases if the evaporative fraction at the land surface increases, which supports boundary layer moistening but only when boundary layer growth is limited by atmospheric factors. This regime was supported by Cabauw observations in the original study. Here, new observational evidence that the tendency of RHtop can also increase as the surface becomes more dry, as is consistent with another regime of the conceptual framework, is provided. The observations used are from the African Monsoon Multidisciplinary Analyses (AMMA) intensive observational campaign near Niamey, Niger, 20–25 June 2006. In addition, the authors evaluate whether various versions of the Weather Research and Forecasting single-column model confirm the different regimes of the conceptual framework for a typical day in the AMMA campaign. It appears that the model confirms that dryer soils can support cloud formation.

scholarly journals Observational and Numerical Evidence of Depressed Convective Boundary Layer Heights near a Mountain Base

2008 ◽  
Vol 47 (4) ◽  
pp. 1017-1026 ◽  
Author(s):  
Stephan F. J. De Wekker
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Layer Growth ◽  
Air Pollutant ◽  
Convective Boundary ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Numerical Studies ◽  
Thermally Driven ◽  
Show Evidence

Abstract Recent field and numerical studies show evidence of the existence of a convective boundary layer height depression near a mountain base. This depression can have implications for air pollutant transport and concentrations in complex terrain. To investigate the mechanisms underlying this phenomenon, idealized simulations with a mesoscale numerical model are performed and combined with available observations. The idealized simulations with a single mountain ridge of various dimensions suggest that the depression evolves in time, is most pronounced in the late afternoon, and becomes larger as slope steepness increases. Observations and modeling results show that the atmosphere is heated more intensely near the mountain base than far away from the mountain base, not only inside the boundary layer but also above. The enhanced heating aloft affects boundary layer growth near the mountain base and is associated with the boundary layer height depression. An analysis of the different terms in the temperature tendency equation indicates that vertical and horizontal advection of warm air, associated with the thermally driven circulation along the mountain slope, play a role in this enhanced heating aloft.

scholarly journals Parameterization of Inversion Breakup in Idealized Valleys. Part I: The Adjustable Model Parameters

2006 ◽  
Vol 45 (4) ◽  
pp. 600-608 ◽  
Author(s):  
N. M. Zoumakis ◽  
G. A. Efstathiou
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Convective Boundary Layer ◽  
Sensible Heat Flux ◽  
Layer Growth ◽  
Heat Fluxes ◽  
Future Research ◽  
Model Parameters ◽  
Sensible Heat ◽  
Convective Boundary

Abstract The factors that affect the atmospheric energy budget approach used in the thermodynamic valley inversion destruction model of Whiteman and McKee are investigated theoretically. The height at which the sinking inversion top meets the rising convective boundary layer to destroy valley inversions can be uniquely determined by the topographic characteristics of the valley and an adjustable model parameter, relating to the fraction of sensible heat flux going to convective boundary layer growth, through a simple parabolic relationship. The time required to break a temperature inversion can be expressed with very good approximation as a simple power-law function of the topographic parameters and the fraction of extraterrestrial solar flux that is partitioned to sensible heat flux in the valley atmosphere. The theoretical estimates compare very favorably to predictions from the bulk thermodynamic model of Whiteman and McKee. A new approach to handle time-dependent sensible heat fluxes is outlined. The paper ends with recommendations for future research.

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