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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’

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Defining Ozone “Recovery”Defining Ozone “Recovery”

A lessening of the ozone decline, followed by an increase in total ozone

“Recovery” occurs when total ozone returned to 1980 levels (or pre-1970 levels)

Look for increase in ozone at specific levels in the atmosphere

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Current Signs of RecoveryCurrent Signs of Recovery

Changes Occurring in the Concentrations of Ozone Depleting Substances (ODSs) in the Troposphere.

Changes Occurring in the Concentrations of ODSs in the Stratosphere

Lessening in total column ozone depletion rate at Northern mid-latitudes (?)

“Stabilization” of Antarctic ozone hole by some metrics (magnitude of minimum)

Global Mixing Ratios of Anthropogenic Halocarbons

490

515

540

pp

t

CFC-12

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

pp

t HCFC-142b

HCFC-141b

260

265

270

275

pp

t

CFC-11

30

50

70

90

110

130

150

1991 1993 1995 1997 1999 2001

pp

t

CH3CCl3 HCFC-22

CCl4

CFC-113

2900

2950

3000

3050

3100

3150

3200

1991 1993 1995 1997 1999 2001

pp

t

GlobalTotal EECl

~6% downfrompeak

900 ppt added for other gases

0.0

1.0

2.0

3.0

4.0

5.0

1991 1993 1995 1997 1999 2001

pp

t

H-1211

H-1301

Montzka et al ., NO

Global Mixing Ratios of Anthropogenic Halocarbons

490

515

540

pp

t

CFC-12

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

pp

t HCFC-142b

HCFC-141b

260

265

270

275

pp

t

CFC-11

30

50

70

90

110

130

150

1991 1993 1995 1997 1999 2001

pp

t

CH3CCl3 HCFC-22

CCl4

CFC-113

2900

2950

3000

3050

3100

3150

3200

1991 1993 1995 1997 1999 2001

pp

t

GlobalTotal EECl

~6% downfrompeak

900 ppt added for other gases

0.0

1.0

2.0

3.0

4.0

5.0

1991 1993 1995 1997 1999 2001

pp

t

H-1211

H-1301

Montzka et al ., NO

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Total Equivalent Chlorine -- Montreal ProtocolTotal Equivalent Chlorine -- Montreal Protocol

0.5

1

1.5

2

2.5

3

3.5

4

Mix

ing

Rat

io o

f E

quiv

alen

t C

hlor

ine

(ppb

v)

1940 1960 1980 2000 2020 2040 2060 2080 2100Year

Equivalent Effective Stratospheric Chlorine

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EECL -- Correlated Projection of Ozone ChangeEECL -- Correlated Projection of Ozone Change

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-5

-4

-3

-2

-1

0

1

2

3

4

Per

cen

t (%

)

1980 1990 2000 2010 2020 2030 2040 2050Year

Total Column Ozone Change

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2-D Models: Trends in Total Ozone2-D Models: Trends in Total Ozone

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WMO 1999 Ozone Assessment Model StudiesWMO 1999 Ozone Assessment Model Studies WMO 1999, total column ozone

10 models intercompared for WMO 2-D models given a specified scenario

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Modeling the RecoveryModeling the Recovery

2-D Models have been primary tools Models with interactive temperature feedback

recover much sooner— ~2025 (models: NOCAR, GSFC-int)— 2035-2070 (SUNY,AER, ULAQ, RIVM, UIUC)— >2070 to >2100 (CSIRO)

Even models with T-feedback have limited dynamical feedbacks

3-D Models now becoming useful, but . . . Some models same as EECL (e.g., Nagashima et

al. (2002) Some respond quicker (Schnadt et al., 2002) Some respond slower (Shindell, 2001; Austin et al.,

2001; Dameris et al., 1998)

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Australian 2-D Model Australian 2-D Model Suggests No Recovery by 2100Suggests No Recovery by 2100

2000 2020 2040 2060 2080 2100

-9

-8

-7

-6

-5

-4

45oN

A1Fl-750

B1

A1FI

Ozone %

change f

rom

1979

Year

1980 1985 1990 1995 2000

-6

-4

-2

0

2

TOMS/SBUV MODEL

Based on Randeniya et al. (2002)

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Modeling studies: Most sensitive factors Modeling studies: Most sensitive factors affecting recoveryaffecting recovery

Cl, Br Minor, if Montreal protocol compliance

N2O Major (Growth inc., slower recovery)

CH4 Minor (Growth inc., slower recovery)

T Major (Decrease, faster recovery)

Dynamics Major (could be faster or slower recovery) If past due to climate change, then likely slower recovery

H2O Major (Increase, slower recovery)

Aerosols Minor, unless major background change

Solar Minor, unless major change in sun output

AircraftLikely to be minor

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Radiative Forcing on ClimateRadiative Forcing on Climate