Date of Award

12-1995

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Clifton E. Dungey, PhD

Abstract

This research was conducted to improve our understanding of the effects of vegetative canopy-induced turbulence on the dispersion of air pollution. The computer model most often used to calculate atmospheric dispersion is the Gaussian plume model, which requires some method to compute the downwind dispersions coefficients. These coefficients are a parameterization of the atmospheric stability or the level of turbulence in the atmosphere. The Environmental Protection Agency's recommended parameterization scheme is the Pasquill-Gifford method. By comparing the Pasquill-Gifford method to the Modified Mitchell method using sigma theta, the standard deviation of the horizontal wind fluctuations, the relative precision of each method is determined and their effects on a Gaussian model can be seen. Contrasting three sites with varying levels of vertical obstructions, the most effective method of measuring the turbulence level was determined to be the sigma theta method. The meteorological data show that the wind direction fluctuates up to 50% more in a forested area when compared to an open field. This larger value translates to an increase in atmospheric turbulence at the forested site, In addition, the resulting output of the Gaussian model showed the forested site having a 3.5 times greater concentration than the open field, showing the effects of the increased turbulence and channeling of wind flow introduced by the forest canopy.

AFIT Designator

AFIT-GEE-ENP-95D-05

DTIC Accession Number

ADA307286

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