1. Once released, pollutants are free to wander
RAQ Train the Trainer
February 26-28, 2007
Once released, pollutants are free to wander

2. Module 3. Meteorology and Transport of Air Pollution in the Mid-Atlantic United States
by K.G. Paterson, Ph.D., P.E. ©2007

3. RAQ Train the Trainer
February 26-28, 2007
Did You Know?
~30% of the nitrogen deposited in Chesapeake Bay is from air pollution

4. Course Goals By the end of this session, you will be able to
RAQ Train the Trainer
February 26-28, 2007
Course Goals
By the end of this session, you will be able to
Explain the role that atmospheric transport processes have on the movement of pollutants in the Mid-Atlantic
Identify atmospheric conditions that can elevate or reduce levels of air pollution

5. RAQ Train the Trainer
February 26-28, 2007
How does this happen?
Nitrogen in the waters of Chesapeake Bay can come from a mix of sources, some local, some not
About 1/3 of the N
is deposited from the air (rivers and runoff are other major sources)
Emissions from basin states (PA, MD, VA, DE, NY, WV) account for about 1/2 of the atmospheric deposition. The other half is transported from more distant sources.
Adapted from:

6. Theory: Global Circulation
Driven by tropical heating
Strong convection in tropics (aids rainfall)
Strong downward air near sub-tropics (dries air)
Influences general placement of certain ecosystems (deserts and rain forests, for example)

7. Theory: Pressure Systems
High pressure system air movement
Clockwise
Downward
Outward
High pressure systems often create
Clear skies (Canadian high)
Hazy skies (Continental high)
Limited vertical mixing
Stagnation
in northern hemisphere

8. Theory: Pressure Systems
RAQ Train the Trainer
February 26-28, 2007
Theory: Pressure Systems
Low pressure systems
Counter clockwise
Upward
Inward
Low pressure systems often create
Rain/storms
Strong mixing
Dispersion
Improved air quality
in northern hemisphere

9. Application: Pressure Systems
RAQ Train the Trainer
February 26-28, 2007
Application: Pressure Systems
A common problem in the summer for the Mid-Atlantic U.S. is the formation of the Bermuda High
Persistent high pressure
Weeks of hot, humid weather
Elevates air pollution levels, particularly haze and PM
Brings upwind emissions to Mid-Atlantic states
Often combines with continental high that builds up pollutant levels through stagnation
Decreases natural cleansing (e.g. rainout, dispersion) of atmosphere from storms

10. Theory: Fronts Fronts are the boundaries between air masses
Cold front: colder (drier) air moving into area of warmer (moist) air
Forces warm air upward, causing storms, cleaning air
Cold air is typically quite clean, thus ending air pollution episodes
Warm front: warm (moist) air moving into area of colder (drier) air
More gradual transition, causing less intense rain, frontal zone is general cleaned of pollutants

11. Theory: Winds Aloft
Low level jet: rapid winds that form at low-altitudes (above surface inversions) during the night.
More common where plains meet mountains due to temperature differences at same altitude above these land features
Form in absence of of fronts and storms
Flows from the SW to NE in the Mid-Atlantic, along the contours of the Appalachians

12. Application: Winds Aloft
This diagram depicts where and when the low level jet forms. Note the dependence on a nighttime surface inversion.

13. Application: Appalachian Trough
RAQ Train the Trainer
February 26-28, 2007
Application: Appalachian Trough
The Appalachian Lee Side Trough diverts the regional transport to the northeast, thereby connecting emissions in the Midwest and Southeast to receptors in the Mid-Atlantic

14. Theory: Sea/Land Breezes
RAQ Train the Trainer
February 26-28, 2007
Theory: Sea/Land Breezes
Coastal locations are prone to additional transport influences from the land/sea interface, driven by temperature differences
Morning Land heats more quickly than sea and creates circulation pattern with a sea breeze
Evening Land cools more quickly and creates circulation pattern with a land breeze
Sun
Sun
radiative
cooling
convection
Land
Sea
Land
Sea

15. Theory: Inversions
Inversion: when a layer of the atmosphere has an inverted temperature profile; temperature increases with altitude
Highly stable layer of air
Suppresses vertical movement of air
Pollution accumulates within or below inversion

16. Application: Inversions
The brown haze from NO2 and other pollutants makes an excellent marker for inversion identification
Elevated inversion
Surface inversion

17. Theory: Inversions Topographical Influences
Valleys, mountains, hills can limit dispersion and allow inversions to persist U U z T Ga Ga U
city
ocean

18. Application: Stability
RAQ Train the Trainer
February 26-28, 2007
Application: Stability
Stability is a measure of the tendency for air to move vertically.
Emission plumes can be an estimator of the stability
Vertical mixing influences ground level concentrations.
Fanning
stable
Looping
unstable
Coning
neutral
Fumigation
elevated inversion
Lofting
ground inversion

19. RAQ Train the Trainer
February 26-28, 2007
Theory: Transport
Transport connects air pollutant point of release to point of impact
Source = Point of release
Receptor = Point of impact
Airshed: The physical extent of all sources which can affect a receptor of interest

20. Theory: Transport Processes
RAQ Train the Trainer
February 26-28, 2007
Theory: Transport Processes
Any given pollutant can be transported by one or more of the following processes in the Mid-Atlantic
Large-scale transport
Global circulation
High/low pressure
Fronts
Smaller-scale transport
Winds aloft
Appalachian trough
Sea/land breezes
Vertical mixing inhibition (inversions)

21. Application: Long Range Transport
RAQ Train the Trainer
February 26-28, 2007
Application: Long Range Transport
For some air quality issues, the Mid-Atlantic U.S. receives considerable upwind contributions from far away, like NOx, as shown here.
©2002 Connecticut Department of Environmental Protection

22. Application: Long Range Transport
Long-range transport can influence local air quality. Example: Canadian forest fires (red dots) affected the Mid-Atlantic U.S. with particulate pollution during this July 7, 2002 event. A high pressure to the southwest of the fires created the southerly flow and a smoke plume several hundred miles in length.
Source: NASA GSFC,

23. Further Learning
Pollutant Transport Analyses, one of the PAMS workshops on ozone transport,
Unisys Weather, online meteorological observations and forecasting,
A Guide to Mid-Atlantic Regional Air Quality, Part III: Meteorology and Transport in Air Pollution Episodes, pp
UCAR Supporting Military Emergency Response During Hazardous Releases.

24. Reflection: Transport
Question: Can we do anything about air pollution transported to our city?
Action: As a class, discuss the ramifications of “living downwind”
Time: 5 minutes

25. Thanks for making this a great class!