Horizontal diffusion in the atmosphere: A Lagrangian-dynamical theory

A form of Langevin's equation is derived that is applicable to the atmospheric diffusion problem. The resulting equation for the particle displacement variance σ2y has limits at small and large diffusion times equal to asymptotic predictions of statistical diffusion theories but provides, in addition, estimates over the broad, middle range of diffusion, which is important in regional and larger-scale atmospheric applications. Predictions of the theory compare well with standard atmospheric diffusion data sets over a range of diffusion times, from seconds to days. When parameters of the theory are determined from short-range plume diffusion data, the theory predicts large-scale eddy diffusivity, K, in the known atmospheric range, a striking confirmation of the ability of this theory to describe atmospheric diffusion.

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