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. 2007/09/27 Aviation & the Environment: Issues & Methods

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

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

How Earth Warms Up The Energy Difference 2007/09/27 Aviation & the Environment: Issues & Methods

Sun & Earth as Blackbodies Note: Earths’ curve magnified by 500,000 times 2007/09/27 Aviation & the Environment: Issues & Methods

Radiation Absorption by Atmospheric Constituents 2007/09/27 Aviation & the Environment: Issues & Methods

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

Aviation & the Environment: Issues & Methods Fuel Combustion 2007/09/27 Aviation & the Environment: Issues & Methods

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

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

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

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

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

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) 2007/09/27 Aviation & the Environment: Issues & Methods

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 2007/09/27 Aviation & the Environment: Issues & Methods

Aviation & the Environment: Issues & Methods Aura Launch July 15, 2004 OMI cut-away diagram 2007/09/27 Aviation & the Environment: Issues & Methods

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

OMI CCD & Optical Assembly 2007/09/27 Aviation & the Environment: Issues & Methods

Observing the Atmosphere from Space 2007/09/27 Aviation & the Environment: Issues & Methods

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

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

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

Aviation & the Environment: Issues & Methods LIDAR MEASUREMENTS Laser pulse Examples: LITE, CALYPSO backscatter by atmosphere EARTH SURFACE 2007/09/27 Aviation & the Environment: Issues & Methods

Hyper-spectral Data Cube 2007/09/27 Aviation & the Environment: Issues & Methods

Remote Sensing & Complexity 2007/09/27 Aviation & the Environment: Issues & Methods

Aviation & the Environment: Issues & Methods In-situ Measurements 2007/09/27 Aviation & the Environment: Issues & Methods

Putting Together Remote Sensing & In-situ Measurements Synergy 2007/09/27 Aviation & the Environment: Issues & Methods

Aviation: the visible (environmental) impact 2007/09/27 Aviation & the Environment: Issues & Methods

Remote Sensing & the Environment (or prelude to conclusions) Aviation Operations 2007/09/27 Aviation & the Environment: Issues & Methods

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

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-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 2007/09/27 Aviation & the Environment: Issues & Methods