In plume models with long averaging times, a correction factor is needed when the hazard time scale th is less than t_plume. Which relation best represents this condition?

In plume models with long averaging times, a correction factor is needed when the hazard time scale th is less than t_plume. Which relation best represents this condition?

• A. <t plume
• B. >t plume
• C. =t plume
• D. not related to plume time

Answer: (A)

The key idea is how the duration of the hazard compares to the time the plume influences a location. When the hazard time scale is shorter than the plume’s residence or averaging time, the short-lived event can be diluted by the long average. In that case, a correction factor is necessary to account for the peak or brief hazard that the long average would otherwise smooth out. This condition corresponds to the hazard time scale being less than the plume time scale.

The key idea is how the duration of the hazard compares to the time the plume influences a location. When the hazard time scale is shorter than the plume’s residence or averaging time, the short-lived event can be diluted by the long average. In that case, a correction factor is necessary to account for the peak or brief hazard that the long average would otherwise smooth out. This condition corresponds to the hazard time scale being less than the plume time scale.