According to Britter and McQuaid, tplume, the average plume correlation time, is approximately:

According to Britter and McQuaid, tplume, the average plume correlation time, is approximately:

• A. 5 minutes
• B. 10 minutes
• C. 20 minutes
• D. 60 minutes

Answer: (B)

Plume correlation time is the time scale over which concentration fluctuations from the plume at a receptor stay related to each other. It tells you how long you can expect the plume’s signal to remain coherent before turbulence and wind changes make successive readings behave more independently. Britter and McQuaid give this tplume as about ten minutes, a value that reflects typical persistence of plume structures under common atmospheric conditions. This makes ten minutes a reasonable middle ground: shorter times like five minutes assume the plume decorrelates quickly, while longer times like twenty or sixty minutes assume far more persistence than is usually observed. Using ten minutes as the reference helps capture meaningful fluctuations without overstating their persistence.

Plume correlation time is the time scale over which concentration fluctuations from the plume at a receptor stay related to each other. It tells you how long you can expect the plume’s signal to remain coherent before turbulence and wind changes make successive readings behave more independently. Britter and McQuaid give this tplume as about ten minutes, a value that reflects typical persistence of plume structures under common atmospheric conditions. This makes ten minutes a reasonable middle ground: shorter times like five minutes assume the plume decorrelates quickly, while longer times like twenty or sixty minutes assume far more persistence than is usually observed. Using ten minutes as the reference helps capture meaningful fluctuations without overstating their persistence.