Questions and Answers
What are the stability classes in the Stability Class system?
What is the dispersion coefficient?
A function of atmospheric conditions and the distance downwind of the release.
What conditions characterize the Convective Boundary Layer?
Stability classes A-D with most mixing occurring in stability class A.
What are the characteristics of Stable Boundary Layer conditions?
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What does Meander refer to in atmospheric conditions?
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What does stability class indicate and why is it important?
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What are the differences between unstable, neutral, and stable atmospheric conditions?
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During what time of day can stable atmospheric conditions typically occur?
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What is surface roughness and how is it related to mean obstacle height?
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What causes plume meander?
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How is the concentration of a passive contaminant at a given location related to the mass release rate?
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How is the concentration of a passive contaminant at a given location related to wind speed?
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How does atmospheric stability relate to the concentration of a passive contaminant?
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How are passive atmospheric diffusion coefficients related to atmospheric stability?
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What is the effect of meander on the concentration of a plume?
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What is the effect of meander on the concentration of a puff?
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What is the difference between a puff and a plume release?
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What is the difference between a continuous and instantaneous release?
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Study Notes
Atmospheric Stability Class
- Stability classes range from A to F, indicating different levels of atmospheric conditions.
- Class A represents very unstable conditions, causing significant turbulence and mixing.
- Class D is neutrally stable, neither aiding nor hindering mixing.
- Class F indicates very stable conditions, resulting in minimal mixing.
Dispersion Coefficients
- These coefficients vary based on atmospheric conditions and the distance from the release point.
- σx indicates the standard deviation of concentration downwind.
- σy represents the standard deviation of concentration across the wind direction.
- σz measures the standard deviation of concentration vertically.
Boundary Layer Conditions
- Convective Boundary Layer (CBL) includes stability classes A-D, characterized by active mixing, particularly class A.
- Stable Boundary Layer (SBL) includes classes D-F, with most mixing in class D and least in class F. Mixing is weaker in SBL than in CBL.
Wind Meander
- Refers to the fluctuation in wind direction, causing a winding path.
- Plume meander is influenced by submesocale wind motions.
Atmospheric Stability Significance
- Stability class indicates atmospheric turbulence, which is crucial for predicting pollutant movement.
- Unstable conditions foster high mixing; stable conditions result in low mixing.
Time of Occurrence for Stable Conditions
- Stable atmospheric conditions typically occur during the night.
Surface Roughness
- Surface roughness relates to the density of obstacles affecting air mixing.
- Rural areas are generally rougher than urban areas, enhancing mixing due to more obstacles like trees.
- Wind profile correlates with mean obstacle height; larger obstacles increase wind speed and mixing.
Passive Contaminant Concentration
- Concentration is directly proportional to the mass release rate; increases with higher mass release.
- Concentration is inversely proportional to wind speed; higher wind reduces concentration.
- Atmospheric stability affects dispersion coefficients. Increased stability leads to higher concentrations but lower dispersion coefficients.
Meander Effects on Plume and Puff Concentration
- Meander reduces plume concentration downwind, covering a larger area and altering direction.
- Meander has no effect on puff concentration but changes the puff's location downwind.
Puff vs. Plume Releases
- Puff releases are instantaneous, averaging 20 seconds, modeled as spherical, with no need to account for meander.
- Plume releases are continuous, averaging 10 minutes, may need adjustments for meander, and have a longer release time relative to travel time.
Continuous vs. Instantaneous Releases
- Continuous releases (plume): extended duration, gradual dispersion.
- Instantaneous releases (puff): occur swiftly, usually within seconds.
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Description
This quiz covers essential concepts related to atmospheric stability classes and dispersion coefficients. You'll learn about the stability classification based on wind speed and sunlight, as well as the significance of dispersion coefficients in atmospheric studies. Perfect for students preparing for an exam on environmental science or meteorology.
