Abstract
Many models exist for predicting the atmospheric transport and dispersion of material following its release into the atmosphere. The purpose of these models may be to support air quality assessments and/or to predict the hazard resulting from releases of harmful materials to inform emergency response actions. In either case it is essential that the user understands the level of predictive accuracy that might be expected. However, contrary to expectation, this is not easily determined from published comparisons of model predictions against data from dispersion experiments. The paper presents and reviews the methods adopted and issues involved in comparing the predictive performance of atmospheric transport and dispersion models to experimental data, by reference to a number of experimental data sets and comparison results. It then presents an approach which is designed to make the performance of atmospheric dispersion models more transparent, through clearly defining the basis on which the comparison is made, and comparing the performance of the chosen model to that of a reference model. Such an approach establishes a clear baseline against which the accuracy of models can be evaluated and the performance benefits of more sophisticated approaches quantified. The use of a simple analytic reference model applicable to continuous ground level releases in open terrain and urban areas is shown as a proof-of-principle.
Highlights
The need to be able to predict urban air quality, regulate emissions from industrial plants and predict the consequences of unexpected releases of hazardous materials, has led to the development of a large number of atmospheric transport and dispersion (AT&D) models of varying levels of complexity
It has led to the development of initiatives, such as harmonisation within atmospheric dispersion modelling for regulatory purposes (HARMO), in order to promote the standardisation and development of AT&D models, and the development of best practice guides and model evaluation protocols, such as that developed under the Cooperation in Science and Technology
The range of performance metrics typically used in model evaluations; The limitations inherent in comparisons made against data obtained from field and wind tunnel experiments; How decisions in the evaluation process affect the results
Summary
The need to be able to predict urban air quality, regulate emissions from industrial plants and predict the consequences of unexpected releases of hazardous materials, has led to the development of a large number of atmospheric transport and dispersion (AT&D) models of varying levels of complexity. RANS and The the LES approaches appear innately superior methods, fields, are well known and solutions are less accurate for low wind speed regions [8,9] Britter and both rely on a series of modelling assumptions, commonly including the eddy-viscosity. Both RANS and the LES approaches appear innately superior to Gaussian methods, Hanna [10]. RANS methods may produce reasonable gradient-diffusion hypotheses The limitations of these approximations, even in the simplest flow both rely on a series of modelling assumptions, commonly including the eddy-viscosity and qualitative results for mean flows, their performance may be speed little better than thatBritter of simple fields, are well known and solutions areactual less accurate forapproximations, low wind regions and flow gradient-diffusion hypotheses. Regardless of the AT&D model used it is essential that robust verification and performance evaluation procedures exist that are applicable to both open terrain and complex urban environments to ‘provide assurance of the robustness of predictions and to guide improvements in the modelling techniques’ [15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
