1. Atmospheric Chemistry & Aviation
Kostas Stefanidis, PhD
Metron Aviation

2. Aviation and the Atmosphere
Aviation emissions are deposited directly into the upper troposphere and lower stratosphere with greater warming effect than aviation emissions on the surface.
Rapid growth in global air travel is anticipated to continue in the near future.
2007/09/27
Aviation & the Environment: Issues & Methods

3. Climatology vs. Meteorology
Climatology (long time scales)
Provides with a description of the mean state of the atmosphere and estimates its variability about that state
Understand the (non-linear) dynamics of climate
Meteorology (short time scales)
Study of the atmosphere with focus on weather forecasting
2007/09/27
Aviation & the Environment: Issues & Methods

4. Earth Radiation Balance
Radiated Energy from the Sun warms the Earth.
Energy radiated from Earth to space cools Earth.
The balance of energy from the Sun and the energy radiated back to space from Earth result an equilibrium.
Atmospheric constituents keep average temperature above black body temperature.
2007/09/27
Aviation & the Environment: Issues & Methods

5. How Earth Warms Up The Energy Difference
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Aviation & the Environment: Issues & Methods

6. Sun & Earth as Blackbodies
Note: Earths’ curve magnified by 500,000 times
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Aviation & the Environment: Issues & Methods

7. Radiation Absorption by Atmospheric Constituents
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Aviation & the Environment: Issues & Methods

8. The Atmospheric Layers
The atmosphere is generally described in terms of layers characterized by specific vertical temperature gradients
The troposphere, which extends from the surface to the tropopause at the approximate altitude of 18 km in the tropics, 12 km at mid latitudes, and 6 to 8 km near the poles, is characterized by a decrease of the mean temperature with increasing altitude. This layer, which contains about 85-90% of the atmospheric mass, is often dynamically unstable with rapid vertical exchanges of energy and mass being associated with convective activity. Globally, the time constant for vertical exchanges is of the order of several weeks. Much of the variability observed in the atmosphere occurs within this layer, including the weather patterns associated, for example, with the passage of fronts or the formation of thunderstorms. The planetary boundary layer is the region of the troposphere where surface effects are important. Its depth is of the order of 1 km, but varies significantly with the time of day and with meteorological conditions. The exchange of chemical compounds between the surface and the free troposphere is directly dependent on the stability of the boundary layer.
Above the troposphere, the atmosphere becomes very stable, as the vertical temperature gradient reverses in a second atmospheric region called the stratosphere. This layer, which extends up to 50 km (the stratopause), contains 90% of the atmospheric ozone. Atypical residence time for material injected in the lower stratosphere is one to three years.
2007/09/27
Aviation & the Environment: Issues & Methods

9. Aviation & the Environment: Issues & Methods
Fuel Combustion
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Aviation & the Environment: Issues & Methods

10. Aviation & the Environment: Issues & Methods
Fuel Combustion
The Perfect Combustion
CnHm + S + N2 + O2  CO2 + H2O + N2 + O2
But in reality
CnHm + S + N2 + O2  CO2 + H2O + N2 + O2
NOx + CO + SOx + Soot + UHC
2007/09/27
Aviation & the Environment: Issues & Methods

11. Possible Impact of Jet Exhaust
Emissions are accumulated at altitude:
CO2
H2O
Soot
Sulfate
Emissions induce changes in atmospheric composition (chemical reactions)
2007/09/27
Aviation & the Environment: Issues & Methods

12. Accumulation of Emissions
Increased Radiative Forcing is caused by:
CO2 , H2O, Soot
Particular matter in exhaust and H2O form jet contrails leading to increased cloudiness
2007/09/27
Aviation & the Environment: Issues & Methods

13. Induced Chemical Changes
NOx (NO, NO2) affects atmospheric levels of ozone and methane.
It is a precursor to Ozone (O3), but
In combination with H2O depletes O3
Oxidizes (CH4) resulting cooling
Emission of NOx to the troposphere typically leads to the formation of ozone, as NO catalyses the oxidation of hydrocarbons and CO. However, it also leads to higher concentrations of the hydroxyl radical (OH), the main oxidizing agent in the lower atmosphere, and hence to greater oxidation of methane. Both ozone and methane have significant radiative effects, and the net radiative forcing of NOx emissions is therefore dependent on the balance between warming due to greater ozone formation and cooling due to greater methane removal.
2007/09/27
Aviation & the Environment: Issues & Methods

14. Emissions Regulations
Current Status
Only Soot, UHC, CO, and NOx are regulated
Reducing the level of emissions requires:
International collaboration (Kyoto protocol)
Improved understanding of interrelationships between various emissions (reduce modeling uncertainties)
2007/09/27
Aviation & the Environment: Issues & Methods

15. Terminology Relating to Atmospheric Particles
Smog
A term derived from smoke and fog, applied to extensive contamination by aerosols. Now sometimes used loosely for any contamination of the air.
Smoke
Small gas-bome particles resulting from incomplete combustion, consisting predominantly of carbon and other combustible material, and present in sufficient quantity to be observable independently of the presence of other solids. Dp  urn.
Soot
Agglomerations of particles of carbon impregnated with "tar," formed in the incomplete combustion of carbonaceous material.
Particle
An aerosol particle may consist of a single continuous unit of solid or liquid containing many molecules held together by intermolecular forces and primarily larger than molecular dimensions (> rn) (can consist of two or more such unit structures held together by inter-particle adhesive forces)
2007/09/27
Aviation & the Environment: Issues & Methods

16. The A-train (Aqua/Aura) Afternoon Constellation
MODIS- Aerosols
AIRS Temperature and H2O Profile
Aqua
1:30 PM
Aura
OMI - Aerosol, HCHO, SO2
OMI & HIRLDS – Trop O3, NO2
TES - Trop O3, CO, CH4, HNO3
1:38 PM
Cloudsat
PARASOL
CALIPSO- Aerosol Profile
PARASOL- Aerosol polarization
CALIPSO
AURA
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Aviation & the Environment: Issues & Methods

17. Aviation & the Environment: Issues & Methods
Aura Launch July 15, 2004
OMI cut-away diagram
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Aviation & the Environment: Issues & Methods

18. Instruments onboard AURA
HIRDLS: High Resolution Dynamics Limb Sounder
MLS: Microwave Limb Sounder
TES; Tropospheric Emission Spectrometer (Limb & nadir mode)
OMI: hyper-spectral imaging (nadir mode, VIS & UV))
2007/09/27
Aviation & the Environment: Issues & Methods

19. OMI CCD & Optical Assembly
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Aviation & the Environment: Issues & Methods

20. Observing the Atmosphere from Space
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Aviation & the Environment: Issues & Methods

21. OBSERVATION BY SOLAR OCCULTATION (UV to near-IR)
“satellite
sunrise”
Tangent point; retrieve vertical profile of concentrations
EARTH
Examples:
SAGE, GOMOS
Recent extensions to lunar and stellar occultation
2007/09/27
Aviation & the Environment: Issues & Methods

22. OBSERVATION BY THERMAL EMISSION (IR, m-wave)
NADIR
VIEW
LIMB VIEW
Absorbing
gas or aerosol T1
Examples: MLS, MOPITT, MIPAS, TES, HRDLS To
EARTH SURFACE
2007/09/27
Aviation & the Environment: Issues & Methods

23. OBSERVATION BY SOLAR BACKSCATTER (UV to near-IR)
absorption
Backscattered
intensity IB
Scattering by
Earth surface
and by atmosphere
EARTH SURFACE
2007/09/27
Aviation & the Environment: Issues & Methods
Examples: TOMS, GOME, SCIAMACHY, OMI

24. Aviation & the Environment: Issues & Methods
LIDAR MEASUREMENTS
Laser pulse
Examples: LITE, CALYPSO
backscatter by
atmosphere
EARTH SURFACE
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Aviation & the Environment: Issues & Methods

25. Hyper-spectral Data Cube
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Aviation & the Environment: Issues & Methods

26. Remote Sensing & Complexity
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Aviation & the Environment: Issues & Methods

27. Aviation & the Environment: Issues & Methods
In-situ Measurements
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Aviation & the Environment: Issues & Methods

28. Putting Together Remote Sensing & In-situ Measurements
Synergy
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Aviation & the Environment: Issues & Methods

29. Aviation: the visible (environmental) impact
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Aviation & the Environment: Issues & Methods

30. Remote Sensing & the Environment (or prelude to conclusions)
Aviation
Operations
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Aviation & the Environment: Issues & Methods

31. Aviation & the Environment: Issues & Methods
Conclusions
The aviation’s effect on the global atmosphere is potentially significant (IPCC 1999)
Improved air traffic operations could reduce aviation emissions
Enhanced modeling of radiative forcing of jet exhaust constituents is required to increase the climate forecasting accuracy.
Modeling Uncertainties
Limited accuracy in quantifying the impact of jet exhaust on the climate
Limited understanding of how the atmosphere and climate will respond to human-induced changes in greenhouse gases over the long term
to improve the scientific understanding and modeling capability to assess aviation climate impacts and reduce key uncertainties associated with these impact
2007/09/27
Aviation & the Environment: Issues & Methods

32. Aviation & the Environment: Issues & Methods
References
P.K. Bhartia: Global Air Quality Study from the A-train, August 2001
D. Jacob: Satellite Observations of Atmospheric Chemistry, August 2001
Aviation and the Global Atmosphere, Intergovernmental Panel on Climate Change
Evaluation of Air Pollutant Emissions from Subsonic Commercial Jet Aircraft, EPA, April 1999, EPA420-R
Reducing the Climate Change Impact of Aviation, Communication from the Commission to the Council, the European Parliament, The European Economic and Social Committee and the Committee of the Regions, Brussels, September 2005, COM(2005) 459 Final
Aviation and the Changing Climate, AIAA
Scientific Assessment of Ozone Depletion; 2002, World Meteorological Organization, Report No. 47
2007/09/27
Aviation & the Environment: Issues & Methods