The Britter-McQuaid plume model's performance is expected to be less reliable as wind speed approaches zero, such as under light and variable winds.

The Britter-McQuaid plume model's performance is expected to be less reliable as wind speed approaches zero, such as under light and variable winds.

• A. True
• B. False
• C. Sometimes
• D. Never

Answer: (A)

When wind is very light, the transport of a plume is dominated by diffusion and local turbulent mixing rather than steady advection. The Britter–McQuaid plume model relies on downwind transport scaling with wind speed and assumes a fairly steady, non-calm flow. As wind speed approaches zero, the advection term shrinks and the model’s assumptions break down, making predicted concentrations and plume location much more sensitive to how turbulence and near-field flows are parameterized. In such calm or highly variable conditions, the model tends to be less reliable, which is why its performance is expected to degrade under light winds.

When wind is very light, the transport of a plume is dominated by diffusion and local turbulent mixing rather than steady advection. The Britter–McQuaid plume model relies on downwind transport scaling with wind speed and assumes a fairly steady, non-calm flow. As wind speed approaches zero, the advection term shrinks and the model’s assumptions break down, making predicted concentrations and plume location much more sensitive to how turbulence and near-field flows are parameterized. In such calm or highly variable conditions, the model tends to be less reliable, which is why its performance is expected to degrade under light winds.