Long Range Transport Mechanism

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Long Range Transport Mechanism
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Regional Scale Dispersion Processes
Day Time MixingRandom Mixing
Wind ShearAxial Mixing
Wind VeerAxial Mixing
Horizontally Spreads pollutants
Horizontally redistributes pollutants
Vertically distributes pollutants
The three transport processes that shape regional
dispersion are wind shear, veer, and eddy motion
or random mixing. Homogeneous hazy airmasses are
create through shear and veer at night followed
by vigorous vertical mixing during the day.
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Regional Scale Dispersion
The degree of of the airmass spreading after a
day of transport is independent of the horizontal
eddy diffusivity coefficient
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Airmass History Model ComparisonHY-SPLIT Vs.
CAPITA Monte Carlo Model
HY-SPLIT NGM wind fields, no mixing Monte
Carlo Model NGM wind fields, mixing
At times individual Airmass histories compared
very poorly
At times individual Airmass histories compared
very well
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Local Flows

• Current regional scale models poorly capture
  local flows
• Complex Terrain
• Land Water Boundaries
• Near source impact
• Concentration are due to local and regional
  contributions

Blumenthal et al., 1997
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Monte Carlo Transport Animations