Atmospheric Chemistry & Aviation
Kostas Stefanidis, PhD
stefanidis@metronaviation.com
Metron Aviation
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.
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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
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Earth Radiation Balance
• 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.
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How Earth Warms Up
The Energy Difference
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Sun & Earth as Blackbodies
Note: Earths’ curve magnified by 500,000 times
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Radiation Absorption by
Atmospheric Constituents
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The Atmospheric Layers
Stratosphere
Tropopause
Troposphere
Planetary Boundary Layer
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Fuel Combustion
CO2 + H2O + N2 + O2
NOx + CO + SOx
+ Soot +UHC
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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
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Possible Impact of Jet Exhaust
• Emissions are accumulated at altitude:
– CO2
– H2O
– Soot
– Sulfate
• Emissions induce changes in atmospheric
composition (chemical reactions)
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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
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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
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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)
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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  0.01 .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 (> 0.001 rn) (can consist of two or more such
unit structures held together by inter-particle adhesive forces)
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The A-train (Aqua/Aura) Afternoon
Constellation
1:38 PM
AURA
Aura
OMI - Aerosol, HCHO, SO2
1:30 PM
Cloudsat
CALIPSO
PARASOL
CALIPSO- Aerosol Profile
PARASOL- Aerosol polarization
OMI & HIRLDS – Trop O3,
NO2
Aqua
MODIS- Aerosols
AIRS Temperature
and H2O Profile
TES - Trop O3, CO, CH4,
HNO3
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Aura Launch July 15, 2004
OMI cut-away diagram
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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))
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OMI CCD & Optical Assembly
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Observing the Atmosphere from Space
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OBSERVATION BY SOLAR OCCULTATION
(UV to near-IR)
“satellite
sunrise”
Examples:
SAGE, GOMOS
Tangent point; retrieve vertical
profile of concentrations
EARTH
Recent extensions
to lunar and
stellar occultation
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OBSERVATION BY THERMAL EMISSION
(IR, -wave)
NADIR
VIEW
LIMB VIEW
Absorbing
gas or aerosol
T1
Examples: MLS, MOPITT,
MIPAS, TES, HRDLS
To
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EARTHAviation
SURFACE
& the Environment: Issues & Methods
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OBSERVATION BY SOLAR BACKSCATTER
(UV to near-IR)
absorption
Backscattered
intensity IB
Scattering by
Earth surface
and by atmosphere
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EARTH SURFACE
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Examples: TOMS, GOME, SCIAMACHY, OMI
LIDAR MEASUREMENTS
Laser
pulse
Examples: LITE, CALYPSO
backscatter by
atmosphere
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EARTH SURFACE
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Hyper-spectral Data Cube
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Remote Sensing & Complexity
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In-situ Measurements
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Putting Together Remote
Sensing & In-situ Measurements
In-situ
Measurements
Modeling
Synergy
Remote
Sensing
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Aviation: the visible (environmental)
impact
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Remote Sensing & the Environment (or prelude to conclusions)
Meterology
Weather
Climatology
Climate
Aviation
Operations
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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
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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-99-013
• 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
• http://mozaic.aero.obs-mip.fr/web/features/information/map.html
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