Prediction of Wind Speed, Direction and Diffusivity under Neutral Conditions for Tall Stacks

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  • 1 Centre for Atmospheric Sciences, Indian Institute of Technology, India
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Abstract

A one dimensional model of the neutral planetary boundary layer is used to predict the wind velocity and coefficient of eddy diffusivity throughout the 2-km planetary boundary layer. Comparison with routine radiosonde observations show that at 500 m, the model predictions of wind speed are within 1.2σ of the observed values where σ is the probable error of the observed values. An interesting correlation between the height of maximum diffusion and length scale (u*/f) of the neutral boundary layer has emerged out of this study.

The velocity and diffusivity profiles from the PBL model are then used in the solution of a three-dimensional advection diffusion equation for the dispersal of nonreactive pollutants in the atmosphere. The results indicate that it is possible to select stack heights to ensure maximum dilution of a pollutant immediately on release and thereby minimize its long-range transport.

Abstract

A one dimensional model of the neutral planetary boundary layer is used to predict the wind velocity and coefficient of eddy diffusivity throughout the 2-km planetary boundary layer. Comparison with routine radiosonde observations show that at 500 m, the model predictions of wind speed are within 1.2σ of the observed values where σ is the probable error of the observed values. An interesting correlation between the height of maximum diffusion and length scale (u*/f) of the neutral boundary layer has emerged out of this study.

The velocity and diffusivity profiles from the PBL model are then used in the solution of a three-dimensional advection diffusion equation for the dispersal of nonreactive pollutants in the atmosphere. The results indicate that it is possible to select stack heights to ensure maximum dilution of a pollutant immediately on release and thereby minimize its long-range transport.

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