A passive release refers to a release where the COTA cloud moves at the same speed and direction as the ambient wind.

A passive release refers to a release where the COTA cloud moves at the same speed and direction as the ambient wind.

• A. The COTA cloud moves at the same speed and direction as the ambient wind
• B. The COTA cloud moves faster than the ambient wind
• C. The COTA cloud moves slower than the ambient wind
• D. The COTA cloud moves perpendicular to the wind

Answer: (A)

A passive release acts like a tracer in the air. The released material has no self-propulsion or buoyant force to push it differently from the surrounding air, so it is carried along by the local wind. As a result, the cloud’s bulk motion matches the ambient wind’s speed and direction, while turbulent diffusion spreads the plume over time. If the cloud moved faster, slower, or perpendicular to the wind, that would indicate additional forces or motions (buoyancy, drag, or shear effects) beyond simple advection, which is not characteristic of a passive release.

A passive release acts like a tracer in the air. The released material has no self-propulsion or buoyant force to push it differently from the surrounding air, so it is carried along by the local wind. As a result, the cloud’s bulk motion matches the ambient wind’s speed and direction, while turbulent diffusion spreads the plume over time. If the cloud moved faster, slower, or perpendicular to the wind, that would indicate additional forces or motions (buoyancy, drag, or shear effects) beyond simple advection, which is not characteristic of a passive release.