Experimental Studies of the Turbulence Structure Parameters of the Convective Boundary Layer

Druilhet, A.; Frangi, Jean-Pierre; Guédalia, D.; Fontan, J.

doi:10.1175/1520-0450(1983)022<0594:esotts>2.0.co;2

Cited by 58 publications

(47 citation statements)

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“…This scale was used by MW89 to scale their top-down variances and by Druilhet et al (1983) to scale aircraft data of humidity variances. In the same way as s * is only suited for scaling scalar statistics in a surface-flux dominated ABL, s * e is only suited for situations where the entrainment flux dominates.…”

Section: Requirements For the Generalised Scalar Scalesupporting

confidence: 92%

“…Another objection may be that the entrainment flux is an internal parameter rather than an external forcing parameter. To circumvent one or both problems one could replace s * e in Equation (5) by another interface scale, for example, the interface scale of Druilhet et al (1983), based on a zeroorder jump model (Garratt, 1992):…”

Section: Applicabilitymentioning

confidence: 99%

“…The scalar entrainment flux is not coupled to the scalar surface flux, and therefore can have any value or sign and can dominate over the influence of the surface flux on scalar statistics. Examples of the ABL in which the statistics of scalars (e.g., water vapour, CO 2 and reactive species) are mainly determined by the entrainment process can be found in e.g., Druilhet et al (1983), Sorbjan (1991), Michels andJochum (1995), De Arellano et al (2004) and Jonker et al (2004).…”

Section: Introductionmentioning

confidence: 99%

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Scaling Variances of Scalars in a Convective Boundary Layer Under Different Entrainment Regimes

Moene

Michels

Holtslag

2006

Boundary-Layer Meteorol

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Abstract.For the presentation and analysis of atmospheric boundary-layer (ABL) data, scales are used to non-dimensionalise the observed quantities and independent variables. Usually, the ABL height, surface sensible heat flux and surface scalar flux are used. This works well, so long as the absolute values of the entrainment ratio for both the scalar and temperature are similar. The entrainment ratio for temperature naturally ranges from −0.4 to −0.1. However, the entrainment ratio for passive scalars can vary widely in magnitude and sign. Then the entrainment flux becomes relevant as well. The only customary scalar scale that takes into account both the surface flux and the entrainment flux is the bulk scalar scale, but this scale is not well-behaved for large negative entrainment ratios and for an entrainment ratio equal to −1. We derive a new scalar scale, using previously published large-eddy simulation results for the convective ABL. The scale is derived under the constraint that scaled scalar variance profiles are similar at those heights where the variance producing mechanisms are identical (i.e., either near the entrainment layer or near the surface). The new scale takes into account that scalar variance in the ABL is not only related to the surface flux of that scalar, but to the scalar entrainment flux as well. Furthermore, it takes into account that the production of variance by the entrainment flux is an order of magnitude larger than the production of variance by the surface flux (per unit flux). Other desirable features of the new scale are that it is always positive (which is relevant when scaling standard deviations) and that the scaled variances are always of order 1-10.

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Section: Requirements For the Generalised Scalar Scalesupporting

confidence: 92%

Section: Applicabilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Scaling Variances of Scalars in a Convective Boundary Layer Under Different Entrainment Regimes

Moene

Michels

Holtslag

2006

Boundary-Layer Meteorol

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“…4f), and in agreement with observations (e.g. Druilhet et al 1983). Secondary peaks of C 2 T and C 2 q that can be observed at 800 m (at 0700 UTC) can be ascribed to turbulent fluctuations at the top of the residual layer during the morning transition.…”

Section: Mean Profilesmentioning

confidence: 99%

The Effect of Surface Heterogeneity on the Structure Parameters of Temperature and Specific Humidity: A Large-Eddy Simulation Case Study for the LITFASS-2003 Experiment

Maronga

Hartogensis

Raasch

et al. 2014

Boundary-Layer Meteorol

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We conduct a high-resolution large-eddy simulation (LES) case study in order to investigate the effects of surface heterogeneity on the (local) structure parameters of potential temperature C 2 T and specific humidity C 2 q in the convective boundary layer (CBL). The kilometre-scale heterogeneous land-use distribution as observed during the LITFASS-2003 experiment was prescribed at the surface of the LES model in order to simulate a realistic CBL development from the early morning until early afternoon. The surface patches are irregularly distributed and represent different land-use types that exhibit different roughness conditions as well as near-surface fluxes of sensible and latent heat. In the analysis, particular attention is given to the Monin-Obukhov similarity theory (MOST) relationships and local free convection (LFC) scaling for structure parameters in the surface layer, relating C 2 T and C 2 q to the surface fluxes of sensible and latent heat, respectively. Moreover we study possible effects of surface heterogeneity on scintillometer measurements that are usually performed in the surface layer. The LES data show that the local structure parameters reflect the surface heterogeneity pattern up to heights of 100-200 m. The assumption of a blending height, i.e. the height above the surface where the surface heterogeneity pattern is no longer visible in the structure parameters, is studied by means of a two-dimensional correlation analysis. We show that no such blending height is found at typical heights of scintillometer measurements for the studied case. Moreover, C 2 q does not follow MOST, which is ascribed to the entrainment of dry air at the top of the boundary layer. The application of MOST and LFC scaling to elevated C 2 T data still gives reliable estimates of the surface sensible heat flux. We show, however, that this flux, derived from scintillometer data, is only representative of the footprint area of the scintillometer, whose size depends strongly on the synoptic conditions.

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“…é a taxa de dissipação molecular (Druilhet et al, 1983). O quarto coeficiente de difusão testado foi desenvolvido por Ulke (2000), e é expresso por:…”

Section: Coeficientes De Difusão Verticaisunclassified

Um Estudo Comparativo Entre Coeficientes de Difusão Verticais na Simulação da Dispersão de Poluentes em uma Camada Limite Convectiva

Leite

Moreira

2016

Rev. bras. meteorol.

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Este trabalho apresenta um estudo comparativo entre diferentes coeficientes de difusão verticais aplicados em um modelo de dispersão para determinação da concentração de poluentes atmosféricos em uma camada limite convectiva. O modelo de dispersão é uma solução semi-analítica da equação de difusão-advecção tridimensional e estacionária, sendo que os resultados das simulações foram confrontados com dados experimentais da literatura. As melhores performances foram obtidas com o coeficiente de difusão proveniente da teoria estatística de Taylor e propriedades espectrais. Entretanto, resultados menos satisfatórios foram obtidos com a parametrização Asymmetric Convective Model version 2 (ACM2), muito usada como uma das opções para camada limite atmosférica no modelo de mesoescala Weather Research and Forecasting (WRF). Palavras-chave: coeficiente de difusão; equação de difusão-advecção; camada limite convectiva. Comparison Between Vertical Eddy Diffusivities in the Simulation of Pollutant Dispersion in a Convective Boundary Layer AbstractThis work presents a comparative study between different vertical eddy diffusivities applied in a dispersion model to determine the concentration of air pollutants in a convective boundary layer. The dispersion model is a semi-analytical solution of stationary three-dimensional advection-diffusion equation and the simulation results were compared with experimental data from literature. The best performances were obtained with the eddy diffusivity from Taylor's statistical theory and spectral properties. However, less satisfactory results were obtained with the parameterization Asymmetric Convective Model version 2 (ACM2), often used as one of the options for the atmospheric boundary layer in the mesoscale model Weather Research and Forecasting (WRF). Keywords: eddy diffusivity; advection-diffusion equation; convective boundary layer. Introdução.Os processos de industrialização e urbanização têm sido crescentes e constantes, de forma que os grandes centros urbanos vivenciam os impactos que a degradação da qualidade do ar acarreta na qualidade de vida da população e também no meio ambiente de modo geral. Em consequência disto, a comunidade científica vêm buscando meios que visem o entendimento dos processos de dispersão das emissões de poluentes na atmosfera e o seu controle, de forma que os modelos de dispersão surgem como uma alternativa prática e rápida por permitirem estudar a dispersão de poluentes de forma controlada.A eficácia dos modelos de dispersão Eulerianos (teoria K) está relacionada diretamente a uma adequada parametrização do coeficiente de difusão (K), por estes serem os responsáveis pela descrição do comportamento físico da difusão de poluentes na atmosfera. Vários pesquisadores Revista Brasileira de Meteorologia, v. 31, n. 4, [518][519][520][521][522][523][524][525][526] 2016

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Experimental Studies of the Turbulence Structure Parameters of the Convective Boundary Layer

Cited by 58 publications

References 0 publications

Scaling Variances of Scalars in a Convective Boundary Layer Under Different Entrainment Regimes

Scaling Variances of Scalars in a Convective Boundary Layer Under Different Entrainment Regimes

The Effect of Surface Heterogeneity on the Structure Parameters of Temperature and Specific Humidity: A Large-Eddy Simulation Case Study for the LITFASS-2003 Experiment

Um Estudo Comparativo Entre Coeficientes de Difusão Verticais na Simulação da Dispersão de Poluentes em uma Camada Limite Convectiva

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