If the surrounding air cools at the same rate as the plume, what is the expected tendency of the plume?

If the surrounding air cools at the same rate as the plume, what is the expected tendency of the plume?

• A. The plume will rise rapidly.
• B. There will be no tendency for the plume to rise or fall due to temperature differences.
• C. The plume will sink to the ground.
• D. The plume will disperse only with wind shear.

Answer: (B)

When buoyancy drives vertical motion, a plume rises if it’s warmer (less dense) than the surrounding air and sinks if it’s cooler (denser). If the surrounding air cools at the same rate as the plume, their density difference stays the same, so there’s no change in buoyancy. The plume becomes neutrally buoyant and has no tendency to rise or fall due to temperature differences. Any further movement would come from its initial momentum, ambient winds, or turbulence rather than buoyancy.

When buoyancy drives vertical motion, a plume rises if it’s warmer (less dense) than the surrounding air and sinks if it’s cooler (denser). If the surrounding air cools at the same rate as the plume, their density difference stays the same, so there’s no change in buoyancy. The plume becomes neutrally buoyant and has no tendency to rise or fall due to temperature differences. Any further movement would come from its initial momentum, ambient winds, or turbulence rather than buoyancy.