SAChE Atmospheric Dispersion (ELA967) Module 2 Practice Test

This term is the vertical Gaussian distribution that describes how the concentration from an emission located at height H is spread and diminishes with height difference. It forms the vertical shape factor of the plume, showing how concentration at height z falls off as the distance from the source height (z − H) increases, scaled by the vertical dispersion parameter σ_z. The larger σ_z is, the more the plume spread in the vertical, and the slower the concentration drops with height. If ground reflection is included, you’d also add a second similar term with (z + H) to represent particles that reflect off the ground and arrive at height z from an image source below the ground. That makes the total vertical profile the sum of the direct contribution and the reflected one. This exponential is not a wind speed correction, which would enter differently in the solution, nor a standalone vertical diffusive adjustment. It specifically encodes the direct vertical distribution of the plume from the source height.