What does a superadiabatic lapse rate indicate about plume dispersion?

What does a superadiabatic lapse rate indicate about plume dispersion?

• A. It indicates a stable atmosphere where the plume tends to sink.
• B. It indicates an unstable condition where the plume disperses readily.
• C. It indicates no buoyant force acting on the plume.
• D. It indicates inversion near the ground.

Answer: (B)

A superadiabatic lapse rate means the temperature drops with height faster than the dry adiabatic rate. In this setup, a rising parcel—like a plume—becomes warmer and less dense than its surroundings as it ascends, so buoyancy continues to act upward. That ongoing buoyancy drives strong vertical motion and mixes the plume efficiently into the atmosphere, leading to rapid dispersion. This is the sign of an unstable environment. In contrast, stable conditions (no buoyant rise) or an inversion near the ground would suppress dispersion, and no buoyant force would not explain the enhanced rise. So the correct interpretation is that the atmosphere is unstable and the plume disperses readily.

A superadiabatic lapse rate means the temperature drops with height faster than the dry adiabatic rate. In this setup, a rising parcel—like a plume—becomes warmer and less dense than its surroundings as it ascends, so buoyancy continues to act upward. That ongoing buoyancy drives strong vertical motion and mixes the plume efficiently into the atmosphere, leading to rapid dispersion. This is the sign of an unstable environment. In contrast, stable conditions (no buoyant rise) or an inversion near the ground would suppress dispersion, and no buoyant force would not explain the enhanced rise. So the correct interpretation is that the atmosphere is unstable and the plume disperses readily.