A Gaussian Moment-Conservation Diffusion Model

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  • 1 Atmospheric Physics Section, Radiological and Environmental Research Division, Argonne National Laboratory, Argonne, IL 60439
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Abstract

A new method of solution of the advection-diffusion equation is developed; the key feature of the method is the approximate conservation of the zeroth, first and second moments of pollutant mass, with the assumption of Gaussian subgrid-scale distributions. Test cases used in evaluation of other numerical dispersion techniques are simulated with the Gaussian moment-conservation (GMC) model; the tests attempt to quantify numerical error and computation time requirements. The GMC technique is found to be computationally rapid and applicable to telescoping grid systems, and to model diffusion accurately. In a limited number of test cases, the GMC technique exhibits a phase speed lag of about 10%, with considerable pseudodiffusion and dispersion of short waves for the advective case when initial gradients are steep.

Abstract

A new method of solution of the advection-diffusion equation is developed; the key feature of the method is the approximate conservation of the zeroth, first and second moments of pollutant mass, with the assumption of Gaussian subgrid-scale distributions. Test cases used in evaluation of other numerical dispersion techniques are simulated with the Gaussian moment-conservation (GMC) model; the tests attempt to quantify numerical error and computation time requirements. The GMC technique is found to be computationally rapid and applicable to telescoping grid systems, and to model diffusion accurately. In a limited number of test cases, the GMC technique exhibits a phase speed lag of about 10%, with considerable pseudodiffusion and dispersion of short waves for the advective case when initial gradients are steep.

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