Which stability class corresponds to very stable conditions?

Which stability class corresponds to very stable conditions?

• A. Stability Class A
• B. Stability Class B
• C. Stability Class C
• D. Stability Class F

Answer: (D)

Very stable conditions occur when the atmosphere is strongly stratified and mixing is suppressed, often with a temperature inversion and light or calm winds. In this situation, vertical mixing is minimal, so pollutants don’t disperse upward as much and can stay concentrated near the ground, which is why ground-level concentrations can build up downwind. On the common stability scale used for dispersion, conditions range from very unstable (lots of turbulence and mixing) to very stable (very little turbulence). The very stable end is the extreme category used for modeling nighttime or calm, stable atmospheres. That end of the scale represents the least mixing and the smallest vertical dispersion, leading to higher concentrations near the source. So, very stable conditions correspond to the most stable end of the scale, not the neutral, slightly stable, or unstable categories.

Very stable conditions occur when the atmosphere is strongly stratified and mixing is suppressed, often with a temperature inversion and light or calm winds. In this situation, vertical mixing is minimal, so pollutants don’t disperse upward as much and can stay concentrated near the ground, which is why ground-level concentrations can build up downwind.

On the common stability scale used for dispersion, conditions range from very unstable (lots of turbulence and mixing) to very stable (very little turbulence). The very stable end is the extreme category used for modeling nighttime or calm, stable atmospheres. That end of the scale represents the least mixing and the smallest vertical dispersion, leading to higher concentrations near the source.

So, very stable conditions correspond to the most stable end of the scale, not the neutral, slightly stable, or unstable categories.