A new model pdf for contaminants dispersing in the atmosphere

This paper illustrates the modelling of the probability density function for the concentration of a scalar dispersing in the atmosphere, using a simple modification of a two state distribution relevant to the hypothetical case of no molecular diffusion. The low concentration values are modelled by means of an exponential distribution, and the high concentration tails by a generalized Pareto distribution. The fits are generally better than those obtained using the beta distribution considered in earlier work. The new model links well with the α-β theory for concentration moments in turbulent flows, discussed in other papers of this special issue of Environmetrics.

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