NATS 101

Lecture 23Air Pollution 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.

Major Air Pollution Episodes of Historic Significance

• Some of the worst events in the last two centuries occurred in London – Key ingredients: calm winds, fog, smoke particles

from coal burning

– 1873 - 700 deaths

– 1911- 1150 deaths

– 1952 - 12,000 deaths (Dec 5 - 9)

• Last event led to the Parliament passing a Clean Air Act in 1956

http://www.atmos.washington.edu/2005Q4/212/Kaufman_health.pdf

Major U.S. Air Pollution Episodes of Historic Significance

• U.S. air quality degraded shortly after the beginning of the industrial revolution

• Coal burning in Central and Midwest U.S. – 1939 St. Louis Smog Nov 28

– 1948 Donora, PA in the Monongahela River Valley

– 20 deaths, 1000’s took ill in 5 days Oct 27

• Prompted Air Pollution Control Act of 1955– Ignored automobiles

Major U.S. Air Pollution Episodes of Historic Significance

• 1960s - NYC had several severe smog episodes • 1950s onward – LA had many smog alerts from

an increase in industry and motor vehicle use• Led to passage of the Clean Air Act of 1970

(updated 1977 and 1990) – Empowered Federal Government to set emission

standards that each state had to meet

U.S. Air Pollution Examples

1963 photo of a severe smog episode in New York City. (Photo: AP/Wide World Photo, EPA Journal Jan/Feb 1990.)

Smog in San Gabriel Valley, 1972. (Photo: EPA.)

Air Pollution in Grand CanyonEven remote areas are

affected by pollution

Canyon on a clear day

Canyon on a smog day

http://apollo.lsc.vsc.edu/classes/met130/notes/ Nice link to Lyndon Valley State College that has useful material for a NATS-type course

Primary PollutantsInjected directly into atmosphere

• Carbon Monoxide (CO) – odorless, colorless, poisonous gas

– byproduct of burning fossil fuels

– body acts as if CO is O2 in blood, can result in death

• Nitrogen Oxides (NOx, NO) – NO - nitric oxide

– emitted directly by autos, industry

Primary Pollutants• Sulfur Oxides (SOx)

– SO2 - sulfur dioxide

– produced largely through coal burning

– responsible for acid rain problem

• Volatile Organic Compounds (VOCs) – highly reactive organic compounds

– released through incomplete combustion and industrial sources

• Particulate Matter (dust, ash, smoke, salt) – 10 um particles (PM10) stay lodged in your lungs

– 2.5 um particles (PM2.5) can enter blood stream

Secondary PollutantsForm in atmosphere from chemical-photochemical

reactions that involve primary pollutants

• Sulfuric Acid H2SO4 – major cause of acid rain

• Nitrogen Dioxide NO2 – brownish hue L.A. Sky Colors

Dec 2000

Mark Z. Jacobson

Secondary Pollutants

• Ozone O3 – colorless gas – has an acrid, sweet smell – oxidizing agent

• Primary and secondary pollutants are found in the two types of smog: – London-type smog – LA-type photochemical smog (LA AQMD)

SMOG = SMOKE + FOG

Human Response to One Hour Pollutant Exposure (Turco, p194)

PollutantConcentration

Part per million by mass

Symptom

CO 10-30 ppmm Time distortion (typical urban level)

100 ppmmThrobbing headache (freeway background, 100 ppmm)

300 ppmmVomiting, collapse (tobacco smoke, 400 ppmm)

600 ppmm Death

CO sticks to hemoglobin, forming carboxyhemoglobin (COHb), which reduces the capacity of hemoglobin to carry O2 to cells

Physiology of Exposure to CO

http://apollo.lsc.vsc.edu/classes/met130/notes/

COHb level is 5%-15% for cig puffers!

Human Response to One Hour Pollutant Exposure (Turco, p194)

PollutantConcentration

Parts per million by mass

Symptom

NO2 0.06-0.1 ppmmRespiratory impact (long term exposure promotes disease)

1.5-5.0 ppmm Breathing difficulty

25-100 ppmm Acute asthma

150 ppmm Death (may be delayed)

Human Response to One Hour Pollutant Exposure (Turco, p194)

PollutantConcentration

Parts per million by mass

Symptom

O3 0.02 ppmm Odor threshold (sweet)

0.1 ppmmNose and throat irritation in sensitive people

0.3 ppmm General nose and throat irritation

1.0 ppmmAirway resistance, headaches (long term lead to premature aging of lung tissue)

Human Response to One Hour Pollutant Exposure (Turco, p194)

PollutantConcentration

Parts per million by mass

Symptom

SO2 0.3 ppmm Taste threshold (acidic)

0.5 ppmm Odor threshold (acrid)

1.5 ppmmBronchiolar constriction Respiratory infection

Table 12-2, p.328

Beijing Air Pollution

http://www.terradaily.com/news/pollution-05zs.html

Beijing smog during 2008 summer olympics

Record Pollution Levels AQI > 300 - Hazardous 11-5-2005 AFP Photo

Where’s Beijing? 11-4-2005

NASA MODIS Visible

Fig. 12-4, p.322

Pollution Knows No Boundaries

April 2001 China Dust Transport Across Pacific

U.S. Pollutant Trends1940-1995

• Most pollutants decreased after the 1970 Clean Air Act

LeadParticulates SO2

VOC’sCONO2 is Leveling Off

Fig. 12-9, p.328

Fig. 12-10, p.329

AQI > 150 for CO, SO2, NO2, O3 and PM

http://www.arb.ca.gov/research/health/fs/pm-03fs.pdf

Table 12-1, p.320

90% total pollutants

10% total pollutants

Fig. 12-2a, p.320

Percentage of Primary

Pollutants

Fig. 12-2b, p.320

Percentage of Primary Sources

Air Pollution Weather

• Strong low-level inversion

Subsidence inversion that diurnal heating does not break or weaken significantly

• Weak surface winds

Persistent surface anticyclone

• Sunny weather for photochemical smog

• Hot weather to accelerate O3 production

Fig. 12-12, p.333

Fig. 12-13, p.333

Top of Mixing Layer

Fig. 12-15, p.334

Valleys Trap PollutantsL.A. is in a basin surrounded by mountains that trap pollutants and usually has onshore flow that creates frequent inversions.

Pollutants can only escape through narrow canyons

Fig. 12-14, p.333

Leading Edge of Sea Breeze and “Smog Front” over Inland SoCal

Air Pollution Dispersion

• Air pollution dispersion is often studied with simple models, termed Box Models.  How is a box defined for the LA basin?

Box Model Boundaries for the LA Basin• Ventilation factor is a simple way of relating concentrations

of pollutants to parameters that modulate the dispersion of pollutants in a local environments.

• An increase in either the mixing height or the wind speed increases the effective volume in which pollutants are allowed to mix.

• The larger the volume, the lower the pollution concentration.• How does a box model work?

Ventilation Factor (VF)

Mixing Height

Length = Wind Speed Time

VF = Mixing Height Wind Speed

Volume ~ Length Height

Acid Rain and Deposition

• Sulfur dioxide (SO2) and oxides of nitrogen (NOx) within clouds (including fog) form acidic particles when they react with water:

SO2 + H2O H2SO4 (sulfuric acid) NOx + H2O HNO3 (nitric acid)

• Acid Rain is worse downstream of the point sources of pollution

• Acid Rain affects Trees, Lakes, Structures• Acid Deposition is a world-wide problem

Fig. 12-17, p.338

pH is logarithmic scale. An one unit change denotes a factor of 10 difference.

pH = 5.6 for pristine rain

Fig. 12-19, p.339

Acidified Forest in Czechoslovakia

http://www.atmos.washington.edu/2005Q4/212/AcidDepositionSlides.pdf

Impact on Aquatic Organisms

http://www.epa.gov/airmarkets/acidrain/effects/surfacewater.html#fish

Sandstone Figure in Germany

1908 1968

Herr Schmidt-ThomsenHerr Schmidt-Thomsen

http://www.atmos.washington.edu/2005Q4/212/AcidDepositionSlides.pdf

Summary

• 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 ActBut It is Degrading in Emerging Economies

• Air Pollution Weather and Air Dispersion• Acid Rain

NATS 101

Lecture Ozone Depletion

Supplemental References for Today’s Lecture

Danielson, E. W., J. Levin and E. Abrams, 1998: Meteorology. 462 pp. McGraw-Hill. (ISBN 0-697-21711-6)

Moran, J. M., and M. D. Morgan, 1997: Meteorology, The Atmosphere and the Science of Weather, 5th Ed. 530 pp. Prentice Hall. (ISBN 0-13-266701-0)

Review: Ultraviolet (UV)

Absorption O2 and O3 absorb UV

(shorter than 0.3 m)

Therefore, reductions in the level of O3 would increase the amount of UV radiation that penetrates to the surface

IR

Ahrens, p 36

UV Visible

Hazards of Increased UV

• Increase number of cases of skin cancers

• Increase in eye cataracts and sun burning

• Suppression of human immune system

• Damage to crops and animals

• Reduction in ocean phytoplankton

Natural Balance of Ozone

Danielson et al, Fig 2.28

Disassociation of O2 absorbs UV < 0.2 mO2 + UV O + O

O3 forms when O2 and O molecules collideO2 + O O3

Disassociation of O3 absorbs 0.2-0.3 m UVO3 + UV O2 + O

Balance exists between O3 creation-destruction

CFC’s disrupts balance

Sources of CFC’s• CFC’s make up many

important products

Refrigerants

Insulation Materials

Aerosol Propellants

Cleaning Solvents

Commonly Used CFC’s

Name Formula Primary Use Residence Time (50% decrease)

CFC-11 CCl3F Propellant ~55 years

CFC-12 CCl2F2 Refrigerant ~100 years

CFC-113 C2Cl3F3 Cleaning Solvent ~65 years

It would take 10-20 years for CFC levels to start falling if all production ended today due to leakage of CFC’s from

old appliances, etc.

Chronology of Ozone Depletion

1881 Discovery of ozone layer in stratosphere

1928 Synthesis of CFC’s for use as a refrigerant

1950s Rapid increase in use of CFC’s

1974 Description of ozone loss chemical reactions

1979 Ban of CFC use in most aerosol cans in U.S.

1980s Growth of CFC use worldwide

1985 Discovery of Antarctic ozone hole

1987 Adoption of Montreal Protocol calling for a 50% reduction in use of CFC’s by 1998

Chronology of Ozone Depletion

1989 Confirmation of ozone declines in mid-latitudes of Northern Hemisphere and in the Arctic

1990 Montreal Protocol amended to require a complete phase out of all ozone depleting chemicals by 2000

1990 U.S. requirement for recycling of CFC’s

1992 Discovery of high levels of ClO over middle and high latitudes of Northern Hemisphere

1992 Further amendment of Montreal Protocol calling for an accelerated phase out by ozone depleting chemicals

2100 Time needed for ozone layer to heal completely?

How O3 is Measured: Dobson Unit

• Ozone can be measured by the depth of ozone if all ozone in a column of atmosphere is brought to sea-level temperature and pressure.

• One Dobson unit corresponds to a 0.01 mm depth at sea-level temperature and pressure

• The ozone layer is very thin in Dobson units.

There are only a few millimeters (few hundred Dobsons) of total ozone in a column of air.

Mean Monthly Total Ozone

Huge decrease in O3 over Antarctica during the period 1979-92.

Setting the StageConditions over Antarctica promote

ozone loss.

Circumpolar vortex keeps air over Antarctica from mixing with warmer air from middle latitudes.

Temperatures drop to below -85oC in stratosphere.

Chemical reactions unique to extreme cold occur in air isolated inside vortex.

Williams, The Weather Book

How Ozone is Destroyed

June: Winter begins.

Polar vortex strengthens and temperatures begin to fall.

July-August: The temperatures fall to below -85oC.

Ice clouds form from water vapor and nitric acid.

Chemical reactions that can occur on ice crystals, but not in air, free chlorine atoms from the CFC.

Williams, The Weather Book

How Ozone is Destroyed

Sept: As sunlight returns in early Spring, stratospheric temperatures begin to rise. Clouds then evaporate, releasing chlorine atoms into air that were ice locked. Free chlorine atoms begin destroying ozone.

Oct: Lowest levels of ozone are detected in early spring.

Nov: Vortex weakens and breaks down, allowing ozone poor air to spread.

Danielson et al, Fig 2.29

Chemistry of the Ozone Hole

Chlorine atoms can be freed from CFC’s by UV reaction

CCl3F + UV CCl2F + Cl

CCl2F2 + UV CClF2 + Cl

C2Cl3F3 + UV C2Cl2F3 + Cl

Once a chlorine atom is freed, it can destroy thousands of ozone molecules before being removed from the air

Cl + O3 O2 + ClO

ClO + O O2 + Cl

Moran and Morgan, Fig 2.19

CFC-11

Annual Cycle of Ozone over SP

http://www.cmdl.noaa.gov/ozwv/ozsondes/spo/index.htmlhttp://www.cmdl.noaa.gov/ozwv/ozsondes/images/ozone_anim2001.avi

Mean Monthly Total Ozone

Decrease in O3 over N.H. during the period 1979 to 1993.

NASA web site

Ozone Hole Statistics

• Daily max ozone hole area (2009): 24 million km2 on 17 September.

• Daily min ozone value area (2009): 94 DU on 26 September.

• Largest ozone hole ever observed: 24 Sept 2006.

Key Points: Ozone Hole

• Chlorofluorocarbons (CFCs) disrupt the natural balance of O3 in S.H. stratosphere

CFCs responsible for the ozone hole over SP!

Responsible for lesser reductions worldwide.

• Special conditions exist in stratosphere over Antarctica that promote ozone destruction:

Air trapped inside circumpolar vortex

Cold temperatures fall to below -85oC

Key Points: Ozone Hole

• CFCs stay in atmosphere for ~100 years

One freed chlorine atom destroys thousands of O3 molecules before leaving stratosphere

• Montreal Protocol mandated total phase out of ozone depleting substances by 2000.

• Even with a complete phase out, O3 levels

Would not increase for another 10-20 years

Would not completely recover for ~100 years