Which statement is true about the dispersion coefficients relative to atmospheric stability?

Which statement is true about the dispersion coefficients relative to atmospheric stability?

• A. They are larger under unstable conditions than under stable conditions.
• B. They are larger under stable conditions.
• C. They are independent of stability.
• D. They depend only on temperature.

Answer: (A)

Turbulent diffusion that governs plume spread is driven by atmospheric turbulence, which is set by stability. When the air is unstable, surface heating creates buoyant eddies and strong vertical mixing, boosting turbulence and increasing dispersion coefficients. In stable conditions, vertical mixing is suppressed by stratification (inversions, calm air), so the dispersion coefficients are smaller. They clearly depend on stability and the resulting turbulence, not just temperature. So the statement that dispersion coefficients are larger under unstable conditions is the correct one.

Turbulent diffusion that governs plume spread is driven by atmospheric turbulence, which is set by stability. When the air is unstable, surface heating creates buoyant eddies and strong vertical mixing, boosting turbulence and increasing dispersion coefficients. In stable conditions, vertical mixing is suppressed by stratification (inversions, calm air), so the dispersion coefficients are smaller. They clearly depend on stability and the resulting turbulence, not just temperature. So the statement that dispersion coefficients are larger under unstable conditions is the correct one.