The Determination of Lateral Diffusivity in Diabatic Conditions near the Ground from Diffusion Experiments

Giichi Yamamoto U.S. Weather Bureau, Washington, D.C.

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Atsushi Shimanuki Geophysical Institute, Tohoku University, Sendai, Japan

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Abstract

The three-dimensional equation of diffusion is solved numerically. Vertical diffusivity derived from the turbulent transfer theory is used, as is an assumed form for the lateral diffusivity containing an unknown parameter with respect to stability. The parameter is determined as a function of stability by comparing the theoretical distribution of concentration with observations made during projects Prairie Grass and Green Glow. The dependence on the averaging time of the lateral diffusivity of smoke concentration is also estimated by use of these experiments. The diffusion patterns in different stability and surface conditions are expressed fairly well by the calculations.

Abstract

The three-dimensional equation of diffusion is solved numerically. Vertical diffusivity derived from the turbulent transfer theory is used, as is an assumed form for the lateral diffusivity containing an unknown parameter with respect to stability. The parameter is determined as a function of stability by comparing the theoretical distribution of concentration with observations made during projects Prairie Grass and Green Glow. The dependence on the averaging time of the lateral diffusivity of smoke concentration is also estimated by use of these experiments. The diffusion patterns in different stability and surface conditions are expressed fairly well by the calculations.

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