A non-Gaussian puff model

A model for the dispersion of passive non-Gaussian puffs is presented. The model is based on a general technique for solving the K-equation on the basis of the truncated Gram-Charlier expansion of the concentration field. The model performances are evaluated against experimental ground-level concentrations, using meteorological data collected near the ground

Air pollution model and neural network: An integrated modelling system

It is well known that neural networks can work as universal approximators of non-linear functions and they have become a useful tool either where any precise phenomenological model is available or when uncertainty complicates the application of deterministic modelling as, for example, in environmental systems. Usually, NN models are using as regression tool. We have developed an integrated modelling system coupling an air dispersion model with a neural network method both to simulate the influence of important parameters on air pollution models and to minimize the input neural net variables. In our approach, an optimised 3-Layer Perception is used to filter the air pollution concentrations evaluated by means of the non-Gaussian analytical model ADMD. We applied this methodology to the wellknown Indianapolis urban data set which deals with a release of pollutants from an elevated emission source

Sensitivity analysis of an operational advanced Gaussian model to different turbulent regimes

A non-reactive air pollution model evaluating ground level concentration is presented. It relies on a new Gaussian formulation (LUPINI R. and TIRABASSI T., J. Appl. Meteor., 20 (1981) 565-570; TIRABASSI T. and RIZZA U., Atmos. Environ., 28 (1994) 611-615) for transport and vertical diffusion in the Atmospheric Boundary Layer (ABL). In this formulation, the source height is replaced by a virtual height expressed by simple functions of meteorological variables. The model accepts a general profile of wind u(z) and eddy diffusivity coefficient Kz . The lateral dispersion coefficient is based on Taylor’s theory (TAYLOR G. I., Proc. London Math. Soc., 20 (1921) 196-204). The turbulence in the ABL is subdivided into various regimes, each characterized by different parameters for length and velocity scales. The model performances under unstable conditions have been tested utilizing two different data sets

THE GROUND LEVEL CONCENTRATION FROM A POINT SOURCE

The Advection-Diffusion Equation (ADE) is solved for a constant pollutant emission from a point-like source placed inside an unstable Atmospheric Boundary Layer (ABL). The solution is obtained adopting the novel analytical approach named Generalized Integral Laplace Transform Technique (GILTT). The concentration solution of the equation is expressed through an infinite series expansion. After setting a realistic scenario through the wind and diffusivity parameterizations the Ground Level Concentration (GLC) is worked out, then an explicit approximate expression is provided for it allowing an analytic simple expression for the position and value of the maximum. Remarks arise on the ability to express value and position of the GLC as an explicit function of the parameters defining the ABL scenario and the source height

Carbon monoxide concentrations evaluated by traffic noise data in urban areas

It is shown that variations in carbon monoxide concentrations can be evaluated by measuring environmental noise, wind velocity and vertical Thermal stability. The results can be justified on the basis of the theory of the street canyon effect. The methodology proposed was verified in two Italian cities with different characteristics: Milan and Ravenna

A surface energy-budget model coupled with a Skewed Puff Model for investigating the dispersion of radionuclides in a sub-tropical area of Brazil

An air pollution model (Skewed Puff Model, SPM) based on the Monin-Obukhov similarity theory was applied to investigate the atmospheric radionuclide dispersion at Iperó in Brazil, the location of a nuclear industrial installation. The SPM numerical simulations were carried out using as input 5-minute averaged wind speed and direction observed at 11.5 m, friction velocity and the Monin-Obukhov length supplied by the surface energy-budget model, along with PBL height, estimated from empirical equilibrium expressions for the nighttime and Mixed-Layer model for the daytime. The agreement between the observed and simulated sensible and latent heat fluxes, friction velocity and Monin-Obukhov length, within a level of confidence of 99.9% indicates that the internal parameters chosen for the surface energy-budget model are representative of the interface soil-vegetation conditions at Iperó. The mean concentration field at the surface was estimated assuming that a hypothetical accident at Iperó produced a continuous emission from a 10 m high point source for 18 hours during the summer of 1993 and for 36 hours during the winter of 1992. The results indicated that, in the case of an accident, the highest concentration values are located near to the source and most of the contaminated area is within a 5 kilometers range, in both seasons. The shape of the contaminated area is defined by the wind speed pattern

A model for the estimation of standard deviation of air pollution concentration in different stability conditions

We propose to estimate the standard deviations of the air pollution concentration in the horizontal and vertical direction, σy and σz, based on Pasquill’s well-known equation, in terms of the wind variance and the Lagrangian integral time scales, on the basis of an atmospheric turbulence spectra model. The main advantage of the spectral model is its treatment of turbulent kinetic energy spectra as the sum of buoyancy and a shear produced part, modelling each one separately. The formulation represents both shear and buoyant turbulent mechanisms characterizing the various regimes of the Planetary Boundary Layer, and gives continuous values at any elevation and all stability conditions from unstable to stable. As a consequence, both the wind variance and the Lagrangian integral time scales in the dispersion parameters are more general than those found in literature, because they are not derived from diffusion experiments as most parameterizations. Furthermore, they provide a formulation continuous for the whole boundary layer resulting more physically consistent. The σy, σz parameters, included in a Gaussian model have been tested and compared with a dispersion scheme reported in the literature, using experimental data in different emission conditions (low and tall stacks) and in several meteorological conditions ranging from stable to convective. Results show that the dispersion model with the sigmas parameterisation included, produces a good fitting of the measured ground-level concentration data in all the experimental conditions considered, performing slightly better than other state-of-art models

Turbulent dispersion from tall stack in the unstable boundary layer: a comparison between Gaussian and K-diffusion modelling for non buoyant emissions

Most air quality dispersionmo dels used for regulatory applications are based onGaussianan d K-diffusionform ulations. The reliability of such models strongly depends on how dispersion parameters and eddy diffusivities are computed on the basis of the update understanding of the Planetary Boundary Layer (PBL) meteorology. In this paper, we compare the performances in simulating pollutants released from continuous point source, by using some Gaussian and K-diffusion models with different assumptions concerning the parameterisation of the dispersionpro cesses. Results show that the Gaussianmo del, inwhic h the dispersion parameters are directly related to spectral peak of turbulence energy, gives the best overall performances. This could be due to a more realistic description of spreading processes occurring into the PBL. This suggests that, in the context of the regulatory applications, this model cangiv e the best combinationb etweengroun d level concentration estimates and computer requirements

A closed form solution for pollutant dispersion in atmosphere considering nonlocal closure of the turbulent diffusion

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Solução Analítica da Equação de Advecção-difusão Considerando Fechamento não-local da Turbulência e Condições de Vento Fraco

Neste trabalho consideramos o fechamento não-local da difusãoturbulenta na equação de advecção-difusão. Obtemos uma solução analíticapara a equação de advecção-difusão usando o método GILTT (GeneralizedIntegral Laplace Transform Technique). Para testar a nova solução analítica,as concentrações máximas obtidas são comparadas com os dados experimentaisdo experimento de ITT Delhi para condições de vento fraco