How does ground reflection affect the Gaussian plume concentration at ground level?

How does ground reflection affect the Gaussian plume concentration at ground level?

• A. Ground reflection creates a mirrored image of the plume, effectively altering the vertical concentration distribution near the ground.
• B. Ground reflection eliminates concentration near the ground.
• C. Ground reflection only affects horizontal distribution.
• D. Ground reflection increases concentration uniformly at all heights.

Answer: (A)

Ground reflection is treated by the method of images: a mirrored copy of the plume is placed below the ground so the boundary at z = 0 is satisfied. The total concentration is the sum of the real plume and this image plume, which changes how the concentration varies with height. Near the ground, both plumes contribute, so the vertical distribution is altered and ground-level concentrations are typically enhanced compared with no-ground effects. This reflection mainly changes the vertical profile rather than producing a uniform increase at all heights or altering only the horizontal spread.

Ground reflection is treated by the method of images: a mirrored copy of the plume is placed below the ground so the boundary at z = 0 is satisfied. The total concentration is the sum of the real plume and this image plume, which changes how the concentration varies with height. Near the ground, both plumes contribute, so the vertical distribution is altered and ground-level concentrations are typically enhanced compared with no-ground effects. This reflection mainly changes the vertical profile rather than producing a uniform increase at all heights or altering only the horizontal spread.