Keywords: atmospheric dispersion, concentration fluctuations, model evaluation, probability, protocols, statistical models
Evaluation of statistical models in atmospheric dispersion modelling
When a gas is released into the atmosphere, there are inevitably random fluctuations in its concentration due to turbulence. Great recent improvements in instrumentation have shown how large these are. This has been acknowledged by CEC (the Commission of the European Communities), for example in that part of its Environment and Climate Programme (Framework IV) dealing with accidents. Likewise, many governmental and commercial organisations now recognise the need for regulatory models to include the effects of fluctuations. Models have been, and still are being, developed. Such models must be stochastic if they are to be realistic; a typical output is the probability that a given concentration is exceeded at a given point and time. Current CEC policy on Model Evaluation does not deal with such models, and this paper focuses on how it may be amended to do so satisfactorily. It is, incidentally, suggested that some re-evaluation of current policy might be in order.