Catálogo de publicaciones - libros

A way to solve the problem of closing the advection-diffusion equation is based on the transport hypothesis by gradient that, in analogy with molecular diffusion, assumes that the turbulent flux of concentration is proportional to the magnitude of the gradient of medium concentration. This work differs from the traditional method; a generic equation is used for the turbulent diffusion being considered that the flux more yours derived is proportional to the medium gradient. This way, an equation is obtained that takes into account the asymmetry in the process of dispersion of atmospheric pollutants. Therefore, the proposal of this work is to obtain an analytic solution of this new equation using the Laplace Transform technique, considering the Convective Boundary Layer (CBL) as a multilayer system. To investigate the influence of the nonlocal effects in the turbulent dispersion process, the model is evaluated against atmospheric dispersion experiments that were carried out in Copenhagen under unstable conditions.

The aim of this work is the formulation of a mathematical model for reacting turbulent flows and its validation through comparison with other models and experimental data. The model is based on the Lagrangian statistical description of the turbulent diffusion, developed firstly for the turbulent dispersion of one particle in homogeneous flows and later gradually extended to non homogeneous flows (Van Dop, 1985) and two-particle dispersion (Durbin, 1980, Thomson, 1990, Borgas and Sawford, 1994).

Three Canadian numerical air quality models: CHRONOS (Canadian Hemispheric and Regional Ozone and NOx System), AURAMS (A Unified Regional Air quality Modelling System) and GEM-AQ (Global Environmental Multiscale – Air Quality model) present different modelling approaches as well as different degrees of complexity in the way they represent the physicochemical interactions of the atmosphere. Large differences also exist in the way these three models are used or the kind of evaluations they have been subjected to. In order to establish a benchmark comparison, the three models will be evaluated over a one month period, starting in August, 2003. Ozone concentrations measured during the same period by air quality monitoring networks will constitute the evaluation database for this work. The three models will be compared in their native mode.

A fundamental problem in the development of an air quality forecast system is the implementation of an evaluation protocol. Traditionally, statistics are computed to compare the model output to the observations. These methods are limited in that they are generally insensitive to location and timing error. In this paper, we describe a framework to address these limitations. This framework adopts a region-based approach and encompasses both formalism and a software tool that is under active development. More specifically, the framework permits the specification and manipulation of invariants associated with topological elements of an air quality forecast.

The spatial distribution of air pollution on the local scale of parts of the territory in Czech Republic is simulated by means of Charles University Lagrangian puff model SMOG nested in NWP model ETA. The results are used for the assessment of the concentration fields of ozone, nitrogen oxides and other ozone precursors. A current improved version of the model based on Bednar et al. (2001) covers up to 18 groups of basic compounds and it is based on trajectory computation and puff interaction both by means of Gaussian diffusion, mixing and chemical reactions of basic species. Results of summer photochemical smog episode simulations are compared to results obtained by another couple adopted in the framework of the national project as a basis for further development of data assimilation techniques, Eulerian CTM CAMx nested in NWP model MM5. There are measured data from field campaigns for some episodes as well as air-quality monitoring station data available for comparison of model results with reality.

MC2-AQ is a multiscale meteorological model combined with an atmospheric air quality module. It is capable of simulating meteorological phenomena and atmospheric chemistry in a wide range of scales, from the regional to the agglomeration scale. High-resolution models, containing comprehensive descriptions of atmospheric chemistry are nowadays applied at spatial resolutions of one kilometre or even higher, despite numerous deficiencies in the available emissions inventories. Hence, a highly important question – quite apart from the general performance assessment of a given model – regarding the results’ reliability limitations due to the quality of the emission database.

In this paper, the problem of forecasting tropospheric ozone concentration is approached by means of nonlinear black-box modeling techniques1. In particular Neuro-Fuzzy, Auto Regressive Ciclostationary and Nonlinear Set Membership models are identified and tested in the one day ahead forecast of daily maximum ozone concentration in Brescia, a highly populated and industrialized area in the Po Valley (Northern Italy). The model performances are assessed by means of indexes and statistical indicators suggested by the European Environment Agency.

The inorganic species of sulfate, nitrate and ammonium constitute a major fraction of atmospheric aerosols. The behavior of nitrate is one of the most intriguing aspects of inorganic atmospheric aerosols because particulate nitrate concentrations depend not only on the amount of gas-phase nitric acid, but also on the availability of ammonia and sulfate, together with temperature and relative humidity. Particulate nitrate is produced mainly from the equilibrium reaction between two gas-phase species, HNO3 and NH3.