SAChE Atmospheric Dispersion (ELA967) Module 2 Practice Test

In this system, atmospheric stability is described by discrete categories that reflect how turbulent the air is and how well pollutants mix. The category that corresponds to a moderate level of instability indicates there’s noticeable turbulence and vertical mixing, but not as intense as the very unstable category. This means pollutants will disperse more than in neutral or slightly stable conditions, but less than under very unstable conditions. So, the idea is that this label represents a middle ground of instability with moderate mixing, not the extremes of stability or instability. The other descriptions don’t fit: very stable conditions come from the stable end of the scale, highly unstable with strong mixing is the very unstable end, and stability isn’t defined by wind speed alone. Also, these categories aren’t meant to be averaged, but are distinct states of atmospheric stability.