The Atmosphere and Atmospheric Ozone

1
The Atmosphere and Atmospheric Ozone

• Dr. Paul A. Newman
• http//code916.gsfc.nasa.gov/People/Newman/
• NASAs Goddard Space Flight Center
• 2005 NASA Earth System Science Teacher Workshop
• NASA GSFC
• April 22, 2005

2
What are the main issues in atmospheric physics?

• Ozone depletion
• Atmospheric pollution
• Climate change
• All 3 issues are related to changing atmospheric
  composition

3
Outline

• Atmospheric Basics Solar Radiation
• Ozone basics and photochemistry
• Ozone loss in the atmosphere
• Summary
• Educational activities

4
Atmospheric Basics
5
Atmospheric Structure
Thermosphere
Mesosphere
Stratosphere
Troposphere
6
Atmospheric Structure
Thermosphere
Mesosphere
Stratosphere
Airliners fly at 30,000-40,000 feet
Troposphere
7
Atmospheric Structure
Thermosphere
Mesosphere
ER-2 flies at 70,000 feet
Stratosphere
Troposphere
8
Atmospheric Structure
Thermosphere
Mesosphere
Oxygen (21)
Nitrogen (78)
Stratosphere
Troposphere
9
Atmospheric Composition

• Nitrogen 0.781
• Oxygen 0.209
• Argon 0.009
• Water 0.014 (tropics)
• 0.002 (poles)
• 0.000004 (stratosphere)
• CO2 0.000360
• O3 0.0000100 (stratosphere)
• 0.0000001 (troposphere)

10
Solar Radiation The photochemistry driver
11
The Electromagnetic Spectrum
Scale (meters)
?-ray
X-ray
UltraViolet
Vis
InfraRed
Radio
Microwave
Baseball
Flea
Cell
E. Coli
Virus
Protein
H2O
Lower Energy
Higher Energy
1 nm 1x10-9 m 1 billionth of a meter
12
1 ?m 1x10-6 m 1 millionth of a meter
13
Absorption of UV by ozone
14
UV radiation

• Solar radiation exists at a variety of
  wavelengths, most commonly visible radiation from
  400 nm (nanometers or billionths of a meter) to
  about 700 nm.
• UV radiation extends from 1-400 nm (invisible to
  the human eye).
• http//sohowww.nascom.nasa.gov/data/realtime-image
  s.html Extreme UV images from the Extreme
  ultraviolet Imaging Telescope (EIT), and the
  Michelson Doppler Imager (MDI)
• A UV photon is more energetic than a visible
  photon, and the UV photon can break the bonds of
  biological molecules such as proteins and DNA.

677 nm visible radiation
04/18/2003 images
30.4 nm UV radiation 60,000-80,000 K
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What is ozone?
16
Atmospheric Structure
Thermosphere
Mesosphere
Stratosphere
Troposphere
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Ozone Facts
Thermosphere
Mesosphere
90 of ozone is in the stratosphere
Troposphere
0
2
4
6
8
Ozone (parts per million)
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Ozone Facts
Thermosphere
Mesosphere
Stratosphere
10 of ozone is in the troposphere
0
2
4
6
8
Ozone (parts per million)
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What does ozone do?Absorbs UV radiation
20
Ozone Facts
Ozone is the Earths natural sunscreen
UVc - 100 Absorption
UVb - 90 Absorption
UVa - 50 Absorption Scattering
Stratosphere
0
2
4
6
8
Ozone (part per million)
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Ozone Facts
Thermosphere
Mesosphere
Ozone is a pollutant, lung and esophagus irritant
Stratosphere
Troposphere
22
UV Health Facts

• UV pluses produces vitamin D in the skin -
  necessary to maintain levels of calcium and
  phosphorus (10-15 minutes twice a week)
• UV minuses
• Eye damage cataracts, photokerititus
  (snowblinding), ocular cancers
• Skin cancers basal, squamous, melanoma
• photoaging
• Damage to various land speciesDamage to aquatic
  species
• Increased pollution levels in urban environments

Cataract
Melanoma
Mexico City
23
Future cancer rate projections
Cases in excess of 1980 levels ( 2000 per
million) Without the protocol, excess cases would
have increase unchecked
24
Changes is surface UV

• Over the last 2 decades, UV radiation that causes
  sunburns has increased about 8 in the northern
  mid-latitudes

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Ozone Photochemistry
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Ozone Absorption of UV
2. An O2 reacts with An O atom to reform O3
1. O3 is split by UV radiation
UV radiation (200-300 nm) converted to heat Net
O3 h? ? O3 At 30 km, this reaction takes 0.1
seconds
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Ozone Production
UV ? lt 240 nm
O O2 M ? O3 M
O2 h? ? 2 O
Ozone is created by oxygen molecules and
energetic UV radiation Net O2 h? ? 2 O3
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Catalytic Ozone Loss
1.

• 1. O3 h? ? O2 O
• 2. O3 X ? O2 XO
• 3. XO O ? O2 X
• Net 2 O3 ? 3 O2

3.
2.
Principal ingredients for ozone loss UV
radiation and a free radical X OH, NO, Cl, Br
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Photochemical balance
30
Source gases for ozone loss
31
Man-made gases destroy ozone
32
Source Gases

• Cl is much more abundant than Br
• Br is about 50 times more effective at O3
  destruction

From Ozone FAQ - see http//www.unep.org/ozone/faq
.shtml
33
Atmospheric Chlorine Trends from NOAA/CMDL -HATS
Group
102 years
CFC-12
50 years
Steady growth of CFCs up to 1992
5 years
42 years
85 years
Figure from Trends of the Commonly Used Halons
Below Published by Butler et al. 1998
34
Photochemical balance
35
Digression - Refrigerant Replacements
36
Whats happened to polar ozone?
37
Antarctic Measurements
Aurora over Halley Bay Station, Antarctica,
75.6ºS 26.5ºE Brunt Ice Shelf, Coats Land 105
days of continuous darkness, twice per year
re-supply Population 65 in summer, 15 in winter
38
Digression Dobson Units

• Total Ozone is a measure of the total column
  amount above us. Measured in Dobson Units
• If we bring all of the ozone above us down to the
  Earths surface
• The thickness would be about 3 millimeters (0.1
  inches) 300 Dobson Units (approximately the
  global average)
• 100 Dobson Units 1 millimeter in thickness

ozone layer
2
10
3 mm 300 Dobson Units

• The Dobson Unit is a convenient unit of
  measurement for total column ozone

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October Antarctic Ozone

• Halley Bay October Averages
• ? Minimum value of October TOMS average

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TOMS - August 31, 2003
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The 2003 Movie
Greg Shirah, NASA/GSFC SVS
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October Average Ozone Hole
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Arctic Antarctic Trends
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Polar Stratospheric Clouds
HCl and ClONO2 react on the surface of cloud
particles, releasing Cl2. As the sun rises in
the spring, the Cl2 is photolyzed by visible
light, starting a catalytic reaction that
depletes ozone 1-2 per day!
Central, Sweden January 14, 2003 - P. Newman
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Global Total Ozone
60S-60N
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Future of Global Ozone Levels
Globally averaged TOMS observations provide the
basis for testing models
47
Whats being done?
48
Atmospheric Chlorine Trends from NOAA/CMDL -HATS
Group
CFC-12
Figure from Trends of the Commonly Used Halons
Below Published by Butler et al. 1998
49
NASA continues to measure ozone and gases that
destroy ozone
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Future Antarctic Ozone Levels
1.Will CFCs and halons decrease as expected?
2. Greenhouse gas warming of the lower atmosphere
has a cooling affect in the stratosphere,
increasing polar O3 loss
3. Stratospheric water vapor increases (of
unknown origin) will increase polar O3 loss
WMO Assessment 2003
51
What Can You Do?

• Avoid excessive solar exposure (limit sun between
  11AM and 2PM).
• Wear and encourage others to wear sunscreen (SPF
  rating of 15). Even with sunscreen, prolonged
  exposure is not smart.
• Check your skin regularly.
• Wear sunglasses that screen UV.
• Hats and other coverings
• Make note of the UV index on the news or web
  http//www.epa.gov/sunwise/uvindex.html

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Summary

• Stratospheric ozone is a critical gas for
  screening solar UV radiation.
• Human produced ozone destroying substances (ODS)
  have caused large losses of ozone over both poles
  and small global losses.
• ODSs have been regulated under international
  agreements and are slowly decreasing. Ozone
  levels should recover within the next 50-70
  years.

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Educational Activities and Resources

• Jeannie Allen (Sr. Science Education Specialist)
  Jeannette_Allen_at_ssaihq.com 301-614-6627
• See handout prepared by Jeannie
• Chem Matters http//chemistry.org/education/chemma
  tters.html

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END
Jan. 10, 2003 - local noon, Kiruna, Sweden
55
Ozone Basic Facts
O3 Ozone is composed of 3 oxygen atoms. O3
inhalation becomes a problem at concentrations
greater than 80 parts per billion sustained
during a continuous 8-hour period (EPA). O3
absorbs harmful solar ultraviolet radiation. A
necessary condition for life. O3 is mainly found
in the the stratosphere. O3 heats the
stratosphere. O3 concentrations are small (peak
concentrations are about 10 parts per million at
an altitude of about 32 km (20 miles). Mass
(Billion Metric Tons) Sun 1,9900,000,000,000,000
,000 Earth 5,980,000,000,000 Global
atmosphere 5,300,000 Global ozone 3
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Digression - Satellite Total Ozone Observations
Solar UV

• First satellite total ozone observations on
  Nimbus-4 in 1970
• Total Ozone Mapping Spectrometer (TOMS) launched
  on Nimbus-7 in 1978
• 90 of UV absorbed by ozone in stratosphere, 90
  of UV reflected by ozone in troposphere
• TOMS uses differential UV absorption to measure
  column ozone

Nimbus-7
UV is absorbed as it passes through the ozone
layer More absorption at shorter wavelength
57
Ozone and climate change

• Ozone change is not a primary cause of climate
  change.
• Ozone depleting substances contribute to climate
  change.
• Ozone changes causes a climate response that is
  generally larger than the Halocarbon response.
• Climate change may seriously impact ozone levels.

See Climate Change 2001 The Scientific Basis
58
What About Global Warming?
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Without the greenhouse effect, the average
surface temperature would be 0º F!
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(No Transcript)
61
(No Transcript)
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Variations of the Earths surface temperature
for the past 1,000 years
63
The last 160,000 years (from ice cores) and the
next 100 years
700
600
500
400
CO2 concentration (ppmv)
CO2 now
300
10
Temperature difference from today C
200
0
10
100
160
120
80
40
Now
Time (thousands of years)
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ATMOSPHERE
OCEANS
LAND

• Only about ½ of the CO2 emitted each year shows
  up in the atmosphere. The rest is absorbed by
  the ocean or by plants on land.

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Feedbacks make predicting future climate
challenging!
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Global Trends
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Global Total Ozone
Data and model show downward trend through 1980s
and 1990s with an apparent solar cycle
superposed. Both have interannual
variability. Model has perturbations from El
Chichon and Pinatubo aerosols. Deduction of
the magnitude of their effect is not obvious
without further analysis.
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Tropospheric Pollution
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Tropospheric Ozone
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Monitoring Timeline
Nimbus-4 BUV
Nimbus-7 SBUV
Nimbus-7 TOMS
NOAA-9
NOAA-11
Meteor-3 TOMS
NOAA-14
Earth Probe TOMS
NOAA-16
Sciamachy
EOS Aura OMI
NPOESS OMPS
2010
1970
1980
1990
2000
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Seasonal changes in the UV index
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Are CFCs are too heavy to get into the
stratosphere?No.
CF4
CFC-12
CFC-12 decreases rapidly because it is photolyzed
by UV radiation
Molecular weights Dry Air 29 CF4 88 CFC-12
121
CFCs are heavier than dry air and could settle
out of a completely still atmosphere. However,
turbulent diffusion mix gases uniformly over the
lowest 100 km of the atmosphere. Above the
homopause, molecular diffusion dominates, and
gases become layered by molecular weight.
Source Report of Concentrations, Lifetimes, and
Trends of CFCs, Halons, and Related Species (NASA
1339)
73
Can we produce ozone to replace the depleted
ozone?Yes, but it would be pointless.

• Ozone is in a photochemical balance between solar
  production and loss by naturally occurring
  hydrogen, nitrogen, chlorine, and bromine
  compounds. Ozone is lost at almost the same rate
  as production. The total amount in our
  atmosphere is about 3 billion metric tons.
• Ozone production is expensive.
• Ozone is produced at a rate of about 0.4 billion
  metric tons per day by UV radiation (242 nm, with
  5 eV for 2 O3 molecules)
• It would take 2 quadrillion BTUs (qBTU) of
  energy to create 0.4 billion metric tons per day
• In 1997 the US produced about 0.2 qBTUs per day
  (coal, gas, oil, nuclear, hydro).

US Energy production
Energy
O3 production
74
Did Mt. Erebus cause the ozone hole?No.

• Volcanoes do inject HCl into the atmosphere, this
  might contribute to stratospheric ozone loss.
• The tropopause is quite low over Antarctica (
  6km)
• Mt. Erebus is quite high (3794 m or 12,450 ft)
• Mt. Erebus
• During active periods, the plume is observed to
  be about 500 m above the peak. Very low
  explosivity index.
• Aircraft measurements of N2O above Mt. Erebus
  indicate that the air in the 12-20 km region has
  descended from the upper stratosphere, not
  injected from the lower atmosphere.

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Volcanic sources of stratospheric chlorine

• Only highly explosive volcanoes inject into the
  stratosphere (VEI gt 4)
• Pinatubo (1991) VEI 5-6
• El Chichon (1982) VEI 5
• Erebus (73-present) VEI 1-2
• Volcanoes produce substantial amounts of HCl
• 2-10 times the total stratospheric Cl burden
• Pinatubo (1991) 4.5 MT
• El Chichon (1982) 1.8 MT
• Erebus (73-present) 0.015 MT/year
• Annual CFC production was on par with volcanic
  sources of Cl
• CFC-11 (1986) 0.35 MT (CFCl3)
• CFC-12 (1986) 0.29 MT (CF2Cl2)
• HCl is water soluble. Since volcanoes produce
  about 1000 times more H2O that HCl, most HCl is
  scavenged from the plume, reducing HCl by factors
  up to 104, as has been shown by aircraft
  observations and rainfall collected from plumes.
• Stratospheric Cl enhancements were small
  following major eruptions
• Pinatubo (1991) lt1 increase (global)
• El Chichon (1982) lt10 increase (global)

Mt. Erebus Antarctica
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History of Ozone and UV
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Digression - The Discovery of Ozone
Joseph Priestly discovers that air is divided
into 2 parts (a substance that retards combustion
and a substance that promotes combustion)
78
Digression - The Discovery of Ozone
In 1776, Antoine Lavoisier repeated many of
Priestleys experiments and correctly recognized
the elementary nature of the gas that he named
oxygen
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Digression - The Discovery of Ozone
Christian Friedrich Schönbein in 1840 recognized
that the odor was not due to the electricity, but
was due to the properties of a substance produced
during the electrical process. He named this
substance ozone (from ozein, Greek for "to
smell").
80
Digression - The Discovery of UV
Johan Wilhelm Ritter uses a prism in 1801 to
discover UV radiation
81
Digression - The Discovery of UV
In 1879, Marie Alfred Cornú used newly-developed
techniques for ultraviolet spectroscopy to
measure the suns spectrum. To his surprise, the
intensity of the suns radiation dropped off
rapidly at wavelengths below about 300 nm.
82
Digression - The Discovery of UV
Hartleys Spectrometer, note prism
83
Digression ozone hole history
Airborne Antarctic Ozone Experiment (AAOE) uses
NASA ER-2 to provide definitive evidence that the
ozone hole is caused by chlorine catalytic
reactions
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Ozone Hole Theory
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Polar Ozone Destruction
1. O3 Cl ? ClO O2
3. ClOOClh??2 ClO2
2 O3
3 O2
2. 2 ClO M ? ClOOCl M
Only visible light (blue/green) needed for
photolyzing ClOOCl No oxygen atoms required Net
2?O3 h? ? 3?O2
86
Polar Processes

• Polar ozone losses differ from the standard
  photochemical balance
• Ozone usually has a very long lifetime months to
  years
• Ozone production is zero, losses are not
  compensated by production
• Very cold conditions, cold enough to form clouds
  in the dry stratosphere.

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Polar Stratospheric Clouds
Central, Sweden January 14, 2003 - P. Newman
88
Antarctic ozone loss

• Cold T ? PSCs high Cly ? het reactions ?
• Large catalytic loss

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Antarctic ozone hole theory
Solomon et al. (1986), Wofsy and McElroy (1986),
and Crutzen and Arnold (1986) suggest reactions
on cloud particle surfaces as mechanism for
activating Chlorine
Cl2 is easily photolyzed by UV blue/green
light HNO3 is sequestered on PSC
90
Chlorine Pathway
Cl catalytically destroys O3
CFC-12 photolyzed in stratosphere by solar UV,
releasing Cl
Cl reacts with CH4 or NO2 to form non-reactive
HCl or ClONO2
?
Carried into stratosphere in the tropics by slow
rising circulation
CFC-12 released in troposphere
91
Why is NASA involved in stratospheric ozone
research?

• Space-based O3 observations developed in the
  1960s
• In early 70s rockets and high altitude aircraft
  exhaust hypothesized as major O3 depleter
• Subsequently CFCs hypothesized as major O3
  depleter
• 1976 NASA Authorization Act charters the
  development and maintenance of a comprehensive
  upper atmosphere research program
• 1977 Clean Air Act Amendment mandates periodic
  reports on ozone to Congress and EPA