1 UIUC UIUC ATMOS 397G ATMOS 397G Biogeochemical Cycles and Biogeochemical Cycles and Global Change Global Change Lecture 5: Atmospheric Lecture 5: Atmospheric Structure / Earth System Structure / Earth System Don Wuebbles Don Wuebbles Department of Atmospheric Sciences Department of Atmospheric Sciences University of Illinois, Urbana, IL University of Illinois, Urbana, IL February 4, 2003 February 4, 2003
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1 UIUC ATMOS 397G Biogeochemical Cycles and Global Change Lecture 5: Atmospheric Structure / Earth System Don Wuebbles Department of Atmospheric Sciences.
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ATMOS 397GATMOS 397GBiogeochemical Cycles and Global ChangeBiogeochemical Cycles and Global ChangeLecture 5: Atmospheric Structure / Earth Lecture 5: Atmospheric Structure / Earth
SystemSystem
Don WuebblesDon Wuebbles
Department of Atmospheric SciencesDepartment of Atmospheric Sciences
University of Illinois, Urbana, ILUniversity of Illinois, Urbana, IL
February 4, 2003February 4, 2003
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Dynamics, Transport, and Chemistry in UT/LSDynamics, Transport, and Chemistry in UT/LS
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Dynamics, Transport, and Chemistry in UT/LSDynamics, Transport, and Chemistry in UT/LS
Courtesy of L. Pan
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Effect of Aircraft Emissions on Ozone Effect of Aircraft Emissions on Ozone Depends on Altitude of the EmissionsDepends on Altitude of the Emissions
0 0.2 0.4
Mach 3.2
Mach 2.4Mach 2.0
Subsonic Fleet
Midlatitude Model
Concentration (mg/M 3)
Altitude (Kilometers)
40
30
20
10
0
Deplete Ozone
Enhance Ozone
NO + O3 --> NO2 + O2
NO2 + O --> NO + O2
O + O3 --> O2 + O2
OH + CO --> H + CO2
H + O2 + M --> HO2 + M
HO2 + NO --> OH + NO2
NO2 + h --> O + NO
O + O2 + M --> O3 + M
CO + 2O2 + h --> CO2 + O3
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Ozone DensityOzone Density
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Total Ozone (Dobson units)Total Ozone (Dobson units)
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Total OzoneTotal Ozone
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Solar Irradiance with AltitudeSolar Irradiance with Altitude
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UV Absorption by OzoneUV Absorption by Ozone
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Formation of OzoneFormation of Ozone
+ M
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Destruction of Ozone: PhotolysisDestruction of Ozone: Photolysis
No net loss of Odd-Oxygen
Oxygen atoms will likely
reform ozone
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Destruction of Ozone: Catalytic Reactions
Cl + O3 ClO + O2
ClO + O Cl + O2
—————————————
Net: O + O3 2O2
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Stratospheric Ozone: Physics and ChemistryStratospheric Ozone: Physics and Chemistry
Production of Ozone The Chapman mechanism -- middle/upper stratosphere
O2 + hν O + O ( < 240 nm)
O + O2 + M O3 + M (M=N2, O2, Ar, etc.)
O3 + hν O2 + O
O + O3 O2
“Smog” chemistry -- troposphere and lower stratosphere
(CH4, CO, HC) + OH HO2
HO2 + NO OH + NO2
NO2 + hν NO + O
O + O2 + M O3 + M
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Stratospheric O3: Physics and Chem. (cont.)Stratospheric O3: Physics and Chem. (cont.)
Destruction of stratospheric ozone Primarily through catalytic mechanisms
Examples:
For X = OH or NO or Cl or Br
X + O3 XO + O2
XO + O X + O2
________________
O + O3 2O2
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There have been large increases in atmospheric concentrations of greenhouse gases and in aerosols over the last century ---
Human activities predominate as the causes of these increases
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Atmospheric ChlorineAtmospheric Chlorine
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Concentration of CFC-12Concentration of CFC-12
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Stratospheric HCl Increase Over 1990sStratospheric HCl Increase Over 1990s
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Current and Potential Stresses on OzoneCurrent and Potential Stresses on Ozone
Human-induced Increasing concentrations of N2O (affects NOx)
Increasing concentrations of CH4 (HOx)
Increasing concentrations of CO2 (T)
Aircraft emissions (NOx, H2O) Solid fuel rockets and space shuttle (HCl) Inc. conc. CFCs, Halons, other halocarbons (Cl, Br) Climate change (T, H2O, winds) Nuclear explosions (NOx)
Natural Solar flux variations; solar events Volcanic eruptions
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Temperature Dependence in Stratospheric Temperature Dependence in Stratospheric ChemistryChemistry
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Observed Trends in Total Ozone Observed Trends in Total Ozone
Updated from Fioletov et al. (2002)
Adjusted for Seasonal, QBO, and Solar Effects
1965 1970 1975 1980 1985 1990 1995 2000
-6
-4
-2
0
2
De
va
ton
(%)
Ground-based data
TOMS zonal means
SBUV-SBUV/2
Merged sate llite data
NIWA ass imilated dataset
60oS - 60oN
1965 1970 1975 1980 1985 1990 1995 2000
-6
-4
-2
0
2
De
via
tion
(%)
90oS - 90oN
TO Adjusted for Seasonal, QBO, and Solar Effects(3 month running mean sm
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Ozone “Hole”Ozone “Hole”
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Antarctic Ozone ‘Hole’: Daily MinimaAntarctic Ozone ‘Hole’: Daily Minima
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Daily Estimated Area of Ozone ‘Hole’Daily Estimated Area of Ozone ‘Hole’