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

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

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

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

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: http://www.deq.state.va.us/air/pdf/air/nitrogen.pdf

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)

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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, http://veimages.gsfc.nasa.gov/3339/Canada.A2002188.1635.2km.jpg

Further Learning Pollutant Transport Analyses, one of the PAMS workshops on ozone transport, http://epa.gov/oar/oaqps/pams/analysis/transport/txpsac.html Unisys Weather, online meteorological observations and forecasting, http://www.wxp.unisys.com A Guide to Mid-Atlantic Regional Air Quality, Part III: Meteorology and Transport in Air Pollution Episodes, pp. 31-46. http://www.marama.org/reports/Guide-MidAtlantic_RegAQ_Final.pdf UCAR Supporting Military Emergency Response During Hazardous Releases. http://www.meted.ucar.edu/dispersion/afwa http://www.meted.ucar.edu/dispersion/basics

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

Thanks for making this a great class!