Keywords: buoyant plumes, concentration fluctuations, atmospheric dispersion, elevated source, Kincaid experiment, maximum ground-, level concentrations, model evaluation, environmental impact assessment, air pollution, environmental pollution, modelling, UK, United Kingdom
The Atmospheric Dispersion Modelling System (ADMS): comparisons with data from the Kincaid experiment
In order to test the ability of a model its results must be compared with experimental data; hence validation work is an essential part of the development of any model. This paper presents the results of a validation study of the UK Atmospheric Dispersion Modelling System (UK-ADMS) version 1.06, a short-range dispersion model, against the results of the Kincaid field experiment. Predictions of inherent variability obtained from the fluctuation module incorporated in UK-ADMS are also presented. Such variability implies a limit to the accuracy that could be expected from even a 'perfect model'. Results show that UK-ADMS 1.06 tended to overpredict close to the source. A possible explanation for this could be that UK-ADMS does not take account of the residual buoyancy that very buoyant plumes have once they impact on the top of the boundary layer. Some simple adjustments were made to the model to allow for this, namely the decorrelation of the vertical component of turbulence and increased penetration of the inversion. Further comparisons with the Kincaid data showed greater agreement between the observations and the model. These improvements have been incorporated in the current version of the model.