Oscillations in the horizontal components of the wind velocity associated with oscillations in ai... more Oscillations in the horizontal components of the wind velocity associated with oscillations in air temperature during low–wind speed episodes are ubiquitous in the stable boundary layer and are labeled as wind meandering. The meandering structure is recognizable by a clear negative lobe in the Eulerian autocorrelation functions of the horizontal wind velocity components and of the sonic temperature and by a corresponding peak at low frequency in the velocity components and temperature spectra. These distinctive features are used to isolate meandering occurrences and to study its properties in relation to the classical description of the planetary stable boundary layer. It is shown that the ratio of the variance of the wind velocity vertical component over the variance of the composite of the wind velocity horizontal components splits the frequency distribution of meandering and nonmeandering events and divides the nocturnal boundary layer in two different regimes characterized by di...
Academia Environmental Sciences and Sustainability, May 6, 2024
An alternative solution to the asymptotic Taylor statistical diffusion theorem (variance of parti... more An alternative solution to the asymptotic Taylor statistical diffusion theorem (variance of particle dispersion) and the asymptotic variance quantifying convergence of averages is presented. The solution approach is to identify a representation of the Dirac delta function for large times in the same integral occurring in both variances. This particular function acts as an effective filter and provides a way to obtain an analytical solution. Considering these asymptotic dispersion parameters in a Gaussian diffusion model, analysis of the simulated concentration results shows that the model reproduces well the experimental ground-level concentration data. The variance between the temporal and ensemble averages is evaluated using turbulent observational data collected in a convective boundary layer. The results show that the difference between the temporal and ensemble means is of the order of 5% for an average time window of 1800 s. The present development can be used in a variety of situations involving different types of turbulence.
In this work employed the Moeng’s LES to apprise the turbulent kinetic energy budget during the d... more In this work employed the Moeng’s LES to apprise the turbulent kinetic energy budget during the daily cycle of CLP. The results obtain ed show the satisfactory description of the terms of the turbulent kinetic energy. Moreover, parameterizations were obtained for the terms of turbulent kinetic energy transport in the convective boundary layer.
The following study deals with meandering of the horizontal mean wind. The main motivation for su... more The following study deals with meandering of the horizontal mean wind. The main motivation for such investigation came from the difficulty in describing contaminant dispersion in meandering conditions. Observational field measurements point out that the autocorrelation function of the horizontal wind components, obtained for the meandering cases, displays an oscillating behavior with the presence of large negative lobes. Such negative lobes are described by an equation containing functions that represent patterns of movement associated to meandering and turbulence. As a consequence, this mathematical formulation connects the turbulence and meandering phenomenon establishing the employment of hybrid parameters in models that describe the meandering dispersion. Therefore, considering this dualistic aspect between meandering and turbulence manifestations, a new set of relations for the turbulence parameterization joined with the meandering of the wind have been developed and are availa...
Air Pollution Modeling and Its Application XIV, 2004
This paper describes the development and testing of an analytical model that simulates the disper... more This paper describes the development and testing of an analytical model that simulates the dispersion of contaminants into a convective boundary layer. The model is based on the advection-diffusion equation which is solved by the Laplace transform technique. This ...
In this work a general method to derive eddy diffusivities in a convective growing turbulence in ... more In this work a general method to derive eddy diffusivities in a convective growing turbulence in the planetary boundary layer is proposed. The method is based in a model for the budget equation describing the 3-D energy density spectrum and the Taylor statistical diffusion theory.
CNR/ISAC – Section of Lecce, Italye-mail: vanabor@smail.ufsm.brSumarioMicrobursts sao corrente de... more CNR/ISAC – Section of Lecce, Italye-mail: vanabor@smail.ufsm.brSumarioMicrobursts sao corrente descendentes intensificadas por pro-cessos termodinâmicos na camada de nuvens Cb. Estes eventos tem cau-sado varios danos e perdas de vidas humanas. Este experimento a tecnicade modelagem Large-Eddy Simulation como uma ferramenta para avaliare similar estes eventos de tempo severo.IntroductionSevere thunderstorms are a common weather feature around deworld and usually generate tornados, strong winds, rail and flash floods.Zipser et al. (2003), found the most intense thunderstorms in the Earthoccurs at Southern South America. Brooks et al. (2003) estimates theregion has up to 60 days/year with favorable severe weather conditions.During the thunderstorm life cycle complex circulations aredeveloped. First intense updrafts currents bring moisture and warm airin to the storm, the liquid water content increases and so the updraftcollapses starting raining forming downdraft currents. During this ...
A Large-Eddy Simulation study of the decay of the TKE during the evening transition in an urban b... more A Large-Eddy Simulation study of the decay of the TKE during the evening transition in an urban boundary layer was performed. A realistic LES is employed to simulatean Urban Turbulence Project in the city of Turin (Italy). The LES simulation result have demonstrated that, during the last stage of decay the t−6 behavior persists after averaging the TKE over the entire boundary layer depth.
Oscillations in the horizontal components of the wind velocity associated with oscillations in ai... more Oscillations in the horizontal components of the wind velocity associated with oscillations in air temperature during low–wind speed episodes are ubiquitous in the stable boundary layer and are labeled as wind meandering. The meandering structure is recognizable by a clear negative lobe in the Eulerian autocorrelation functions of the horizontal wind velocity components and of the sonic temperature and by a corresponding peak at low frequency in the velocity components and temperature spectra. These distinctive features are used to isolate meandering occurrences and to study its properties in relation to the classical description of the planetary stable boundary layer. It is shown that the ratio of the variance of the wind velocity vertical component over the variance of the composite of the wind velocity horizontal components splits the frequency distribution of meandering and nonmeandering events and divides the nocturnal boundary layer in two different regimes characterized by di...
Academia Environmental Sciences and Sustainability, May 6, 2024
An alternative solution to the asymptotic Taylor statistical diffusion theorem (variance of parti... more An alternative solution to the asymptotic Taylor statistical diffusion theorem (variance of particle dispersion) and the asymptotic variance quantifying convergence of averages is presented. The solution approach is to identify a representation of the Dirac delta function for large times in the same integral occurring in both variances. This particular function acts as an effective filter and provides a way to obtain an analytical solution. Considering these asymptotic dispersion parameters in a Gaussian diffusion model, analysis of the simulated concentration results shows that the model reproduces well the experimental ground-level concentration data. The variance between the temporal and ensemble averages is evaluated using turbulent observational data collected in a convective boundary layer. The results show that the difference between the temporal and ensemble means is of the order of 5% for an average time window of 1800 s. The present development can be used in a variety of situations involving different types of turbulence.
In this work employed the Moeng’s LES to apprise the turbulent kinetic energy budget during the d... more In this work employed the Moeng’s LES to apprise the turbulent kinetic energy budget during the daily cycle of CLP. The results obtain ed show the satisfactory description of the terms of the turbulent kinetic energy. Moreover, parameterizations were obtained for the terms of turbulent kinetic energy transport in the convective boundary layer.
The following study deals with meandering of the horizontal mean wind. The main motivation for su... more The following study deals with meandering of the horizontal mean wind. The main motivation for such investigation came from the difficulty in describing contaminant dispersion in meandering conditions. Observational field measurements point out that the autocorrelation function of the horizontal wind components, obtained for the meandering cases, displays an oscillating behavior with the presence of large negative lobes. Such negative lobes are described by an equation containing functions that represent patterns of movement associated to meandering and turbulence. As a consequence, this mathematical formulation connects the turbulence and meandering phenomenon establishing the employment of hybrid parameters in models that describe the meandering dispersion. Therefore, considering this dualistic aspect between meandering and turbulence manifestations, a new set of relations for the turbulence parameterization joined with the meandering of the wind have been developed and are availa...
Air Pollution Modeling and Its Application XIV, 2004
This paper describes the development and testing of an analytical model that simulates the disper... more This paper describes the development and testing of an analytical model that simulates the dispersion of contaminants into a convective boundary layer. The model is based on the advection-diffusion equation which is solved by the Laplace transform technique. This ...
In this work a general method to derive eddy diffusivities in a convective growing turbulence in ... more In this work a general method to derive eddy diffusivities in a convective growing turbulence in the planetary boundary layer is proposed. The method is based in a model for the budget equation describing the 3-D energy density spectrum and the Taylor statistical diffusion theory.
CNR/ISAC – Section of Lecce, Italye-mail: vanabor@smail.ufsm.brSumarioMicrobursts sao corrente de... more CNR/ISAC – Section of Lecce, Italye-mail: vanabor@smail.ufsm.brSumarioMicrobursts sao corrente descendentes intensificadas por pro-cessos termodinâmicos na camada de nuvens Cb. Estes eventos tem cau-sado varios danos e perdas de vidas humanas. Este experimento a tecnicade modelagem Large-Eddy Simulation como uma ferramenta para avaliare similar estes eventos de tempo severo.IntroductionSevere thunderstorms are a common weather feature around deworld and usually generate tornados, strong winds, rail and flash floods.Zipser et al. (2003), found the most intense thunderstorms in the Earthoccurs at Southern South America. Brooks et al. (2003) estimates theregion has up to 60 days/year with favorable severe weather conditions.During the thunderstorm life cycle complex circulations aredeveloped. First intense updrafts currents bring moisture and warm airin to the storm, the liquid water content increases and so the updraftcollapses starting raining forming downdraft currents. During this ...
A Large-Eddy Simulation study of the decay of the TKE during the evening transition in an urban b... more A Large-Eddy Simulation study of the decay of the TKE during the evening transition in an urban boundary layer was performed. A realistic LES is employed to simulatean Urban Turbulence Project in the city of Turin (Italy). The LES simulation result have demonstrated that, during the last stage of decay the t−6 behavior persists after averaging the TKE over the entire boundary layer depth.
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