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NATS 101 Air Pollution Meteorology. Where are your clickers?. Hazy skies over Tucson. What is Air Pollution?. AMS Glossary of Meteorology. air pollution —The presence of substances in the atmosphere, particularly those that do not occur naturally.

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nats 101 air pollution meteorology

NATS 101Air Pollution Meteorology

Where are your clickers?

Hazy skies over Tucson

ams glossary of meteorology
AMS Glossary of Meteorology
  • air pollution—The presence of substances in the atmosphere, particularly those that do not occur naturally.
  • These substances are generally contaminants that substantially alter or degrade the quality of the atmosphere.
  • The term is often used to identify undesirable substances produced by human activity, that is, anthropogenic air pollution.
  • Air pollution usually designates the collection of substances that adversely affects human health, animals, and plants; deteriorates structures; interferes with commerce; or interferes with the enjoyment of life.
how beijing looked before the 2008 olympics

How Beijing looked—before the 2008 Olympics….

Economic growth—but at what environmental cost??

China’s current industrial development is actually very similar to the experience in the U.S. and Europe.


Rapid industrialization and natural resource exploitation, necessary to maintain a high economic growth rate.

Heavy dependence on fossil fuels (coal, oil, natural gas) for the energy supply

Fewer pollution or environmental controls.

Pollution is so bad that it is a major threat to public health and the environment.

london smog smog smoke fog
London Smog(“Smog” = Smoke + Fog)

Some of the worst events in the last two centuries occurred in London.

1952 Event resulted in 4000 deaths!

Key ingredients: calm winds, fog, smoke particles from coal burning.

Motivated parliament to pass a Clean Air Act in 1956.

the u s wasn t doing any better especially in big industrial cities in the northeast and midwest
The U.S. wasn’t doing any better, especially in big industrial cities in the Northeast and Midwest.

Smog in New York City


air pollution from burning of coal
Air pollution from burning of coal

Much of the air pollution in the eastern part of the United States was and is still due to burning of coal.

Many of the coal plants today are located on or near the Ohio River


Other places with a similar story:

Rhine River Valley in Germany

Northern China (Manchuria)

the u s passed its air pollution control act in 1955

The U.S. passed its air pollution control act in 1955.

But this act left out one VERY BIG thing!

pollution from vehicle transportation sources was a rapidly growing problem

Pollution from vehicle transportation sources was a rapidly growing problem

But it was a new kind of pollution,

different from the traditional smog

of London or U.S. eastern cities.

And the worst place for it in America was (and still is) Los Angeles

pollution controls on vehicles
Pollution controls on vehicles

Photochemical smog, was a rapidly growing problem

This problem was especially prevalent in western U.S. cities, like Los Angeles.

Severe air pollution lead to the Clean Air act of 1970 and the establishment of the EPA.

This act and its subsequent additions placed emission control standards on vehicles that each state must meet.

Los Angeles in the 1960s

even with the clean air act and the epa air pollution is still a big problem in the u s today

Even with the Clean Air Act and the EPA, air pollution is still a big problem in the U.S. today.

Reason: Though today’s cars are less polluting, there are a lot more of them and people drive farther in them than three decades ago.

you ve got to have a car in l a
You’ve got to have a car in L.A.

Current L.A. freeway system

“Spaghetti Junction” in L.A.

How did it get this way?

Urban mass transit systems dismantled (i.e. trolley systems)

Freeways built and suburban development followed—along with killer commutes. Then more freeways built…

Similar story all across the United States…and it still continues today!

photochemical smog los angeles type smog

L.A. Sky Colors Dec 2000

Mark Z. Jacobson

Photochemical smog(Los Angeles type smog)

Downtown L.A. on a smoggy day

Photochemical smog: Ozone near the ground, caused by chemical reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOC) in the presence of sunlight.

What are the health effects of living in this??


But photochemical smog is not unique to Los Angeles, it occurs in every major city in the Southwest U.S.

arizona is one of the fastest growing states in america

Arizona is one of THE fastest growing states in America!

Maricopa, Arizona

Grew to a population of 40,000 people within just three years!

(Most people who live there drive to the Phoenix area to work…)

Phoenix, Arizona

6th largest city in the U.S.

NEARLY THE SAME in other western U.S. cities, like Denver, Salt Lake City, Albuquerque, and Las Vegas!


Las Vegas, Nevada

Phoenix, Arizona

Denver, Colorado

Salt Lake City, Utah

you can t escape it if you leave the cities either
You can’t escape it if you leave the cities either…

Grand Canyon on a

clear day.

Grand Canyon on a

smoggy day.

two types of air pollutants
Two types of air pollutants

Primary pollutants

Enters the atmosphere directly from (anthropogenic) sources.


Secondary pollutant

Forms as a result of chemical reactions between primary pollutant(s) and/or some other atmospheric constituent.

Examples: photochemical smog and acid rain

primary pollutants
Primary Pollutants

Particulate Matter

Solid particles and liquid droplets that are small enough to remain suspended in the air

Particles less than 10 microns are more likely they are to get into the lungs and affect the body.

Since hygroscopic, they serve as cloud condensation nuclei.

Resulting wet haze is common in the eastern U.S. in the summertime.

Washington, DC in summer.

Sulfur Dioxide (SO2)

Colorless gas that comes primarily from burning of coal and oil.


more primary pollutants
More Primary Pollutants

Carbon monoxide (CO)

Forms by incomplete combustion of carbon-containing fuels. Can be lethal in high concentrations because it replaces oxygen in the blood.

Nitrogen oxides (NOx)

Gases that form when some of the nitrogen in the air reacts with oxygen during fuel combustion process. Can be harmful to respiratory and cardiovascular systems and is carcinogenic.

Volatile organic compounds (VOCs)

Mainly complex hydrocarbon compounds emitted during combustion.


formation of photochemical smog
Formation of photochemical smog

Nitrogen oxide (NOx) Part:

Photodissociation of NO2:

NO2 + sunlight  NO + O

Oxygen radical (O) combines with third molecule (M) to form ozone (O3):

O2 + O + M  O3 + M


Volatile Organic Compound (VOC) Part:

Photodissociation of ozone:

O3 + sunlight  O2 + O

Oxygen radical (O) combines with water (H2O) to form hydroxyl radicals (OH)

O + H2O  OH + OH

Hydroxyl radicals react with VOCs (RH), which then removes nitric oxide (NO)

OH + RH  R + H2O

RO2 + NO  NO2 + other products.


controls on production of photochemical smog
Controls on Productionof Photochemical Smog

Ozone production is controlled by sunlight. Maximized in the afternoon

Ozone production is either NOx limited or VOC limited. Ozone production maximized at ratio of VOC’s to NOx = 8:1

favorable factors for severe air pollution in southwest u s
Favorable factors for severe air pollution in Southwest U.S.

Big metropolitan areas with a lot of vehicles

Lots of sunshine

Meteorological conditions that “trap” the air over a metro area for a long time. Most ideal combination:

Weak winds

City is located under an inversion.

City is located in a basin or valley surrounded by mountains


meteorological conditions under an inversion
Meteorological conditions under an inversion

Recall an inversion is when temperature increases with height.

The inversion forms a ________ layer, (like a lid) which prevents the pollutants from escaping.

Pollution spreads out at the top of the inversion.

What meteorological conditions would be conducive for formation of an inversion?

topographic influence
Topographic influence

Los Angeles is located in a basin.

Surrounded on three sides by mountains

When the winds are weak, the mountains are a physical barrier that prevent pollution from escaping.

Topography of the L.A. Basin

phoenix is a lot like los angeles
Phoenix is a LOT like Los Angeles!

Satellite image of Phoenix area.


Smog trapped in a subsidence inversion in a valley.

This is something you would probably see from the mountains looking down at Los Angeles or Phoenix on a sunny and calm day.

meet mexico city the worst place for air pollution in the north america
Meet Mexico City: THE WORST place for air pollution in the North America


Located at high elevation

surrounded by very high mountains on three sides

A dry and sunny winter under a ridge of high pressure most of the time.

A population of about 9 million people.

Lower environmental standards than U.S.

Smog in Mexico City


no the world
No, the World!

Air pollution is a major health issue in the world’s megacities, especially in developing and relatively poor countries

national air quality standards
National Air Quality Standards

These are the federal standards for air pollution measurements.

If pollution levels exceed these standards, then an area is in “non-attainment”


Our environmental record DOES show some progress in reducing air pollution, but we still have a long way to go.



Though London-type smog in the eastern U.S. has lessened in recent years, coal burning in the Ohio Valley and surrounding areas is associated with another problem…

Why does most acid rain in North America occur north and east of this region?

Ohio River coal power plant

brief review of basic chemistry of acids and bases
Brief Review of Basic Chemistry of Acids and Bases

Acidity: Refers to the concentration of hydrogen (H+) ions.

Alkalinity: Refers to the concentration of hydroxide (OH-) ions.

The degree of acidity or alkalinity is given by the pH scale (1-14).

Acids are at the low end of the scale

pH of 7 is neutral

Bases are at the high end of the scale

Characteristics of strong acids

Sting and burn the skin

Highly corrosive


ph scale degree of acidity and alkalinity
pH Scale: Degree of Acidity and Alkalinity

Natural rain is slightly very weakly acidic (pH = 5 to 6)

Acid rain has a pH of about 4 to 4.5

The pH is scale is LOGARITHMIC, so for each numerical value lower on the scale, it is ______ times more acidic.

Acid rain is about __________ times more acidic than natural rain.

acid rain chemistry
Acid rain chemistry
  • Sulfur dioxide (SO2) and nitrogen oxides (NOx) are emitted as primary pollutants, mainly from coal burning.
  • When these primary pollutants interact with a cloud water drop, acidic particles are formed:
    • SO2 + H2O  H2SO4 (Sulfuric acid)
    • NOx + H2O  HNO3 (Nitric acid)
  • The clouds carrying the acidic drops are carried downwind of the pollution source(s) by the prevailing winds.

In the mid-latitudes, acid rain typically occurs ______________ of polluting sources because of the path of mid-latitude cyclones.

acid rain in the u s
Acid Rain in the U.S.

Most acidic rain in the eastern part of the country, downwind of coal plants in the Ohio River Valley area. Where are the worst places?

effects of acid rain
Effects of Acid Rain

In many eastern U.S. forests, acid rain has lead to severe tree damage by changing the soil chemistry.

Freshwater aquatic ecosystems are particularly sensitive to changes in acidity.

Many small lakes in New York’s Adirondack Park, for example, are no longer able to support fish populations.

Damaged trees in the Smoky Mountains

central and eastern europe have also been severely affected by the acid rain problem

Central and Eastern Europe have also been severely affected by the acid rain problem


Downwind of Rhine industrial zone in Northern Germany

Old and highly polluting coal plants (that are still operating) in former communist countries, like Czechoslovakia, Poland, and former East Germany

acid rain effects on buildings and monuments
Acid Rain Effects on Buildings and Monuments

Same figure


Sandstone figure in Germany


  • Air Pollutants – Long History
    • Primary: CO, NOx, SOx, VOC, PM
    • Secondary: H2SO4, NO2, O3
  • Global Problem - Knows No Boundaries!
    • Serious Health Consequences
  • US Air Improving - Clean Air Act

But It is Degrading in Emerging Economies

  • Air Pollution Weather and Air Dispersion
  • Acid Rain
assignment for next lecture ozone hole climate change
Assignment for Next LectureOzone Hole, Climate Change
  • Reading-Ahrens

3rd: 319-324; 371-396

4th: 325-327+330; 373-399

5th: 334-337; 383-411

  • Homework11-D2L (Due Monday May 7)

3rd-Pg 336: 12.10, 11; Pg. 396: 14.5, 6, 7, 10

4th-Pg 340: 12.10, 11; Pg. 399: 14.5, 6, 7, 10

5th-Pg 350: 12.10, 11; Pg. 412: 14.5, 6, 7, 10