Springer Online Journal Archives 1860-2000
Abstract A method for calculating turbulent diffusion in the planetary boundary layer is developed based on Donaldson's second-order closure approach. The resulting partial differential equation for the turbulent mass flux has a hyperbolic character for early times when the plume scale is small compared with the ambient turbulent scale, with a smooth transition to a parabolic, gradient-diffusion-type character when the plume scale is large. Calculations are compared with available estimates from the literature for different values of Rossby number and Richardson number in the ambient atmosphere. Comparison of model predictions with laboratory simulation of diffusion in a free convection, mixed layer is good, with the model able to predict the maximum concentration rising from the ground as observed.
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