In a very stable atmosphere, how does it influence the time for a plume to reach a given ground height?

In a very stable atmosphere, how does it influence the time for a plume to reach a given ground height?

• A. It speeds up vertical mixing.
• B. It slows vertical mixing, keeping the plume lower for longer.
• C. It has no effect on the time.
• D. It causes the plume to dry out before reaching ground.

Answer: (B)

In very stable air, vertical motion and turbulence are strongly suppressed. The atmosphere resists lifting and mixing, so the plume’s buoyant rise and entrainment of surrounding air are limited. As a result, the plume stays confined to lower altitudes for a longer time and spreads more horizontally rather than lofting upward quickly. This means it takes more time for the plume to reach a given ground height (especially higher elevations or receptors at greater heights). So the stable conditions slow vertical mixing, keeping the plume lower for longer.

In very stable air, vertical motion and turbulence are strongly suppressed. The atmosphere resists lifting and mixing, so the plume’s buoyant rise and entrainment of surrounding air are limited. As a result, the plume stays confined to lower altitudes for a longer time and spreads more horizontally rather than lofting upward quickly. This means it takes more time for the plume to reach a given ground height (especially higher elevations or receptors at greater heights). So the stable conditions slow vertical mixing, keeping the plume lower for longer.