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3. Aviation-Produced Aerosols and Cloudiness
Executive Summary
3.1. Introduction
3.2. Aerosol Emission and Formation in Aircraft Plumes
3.2.1. Volatile Aerosol Precursors
3.2.1.1. Water Vapor
3.2.1.2. Sulfur Species
3.2.1.3. Chemi-ions
3.2.1.4. Nitrogen Species
3.2.1.5. Hydrocarbons
3.2.2. Volatile Particles
3.2.2.1. Basic Processes
3.2.2.2. Observations and Modeling
of Volatile Particles and Sulfur Conversion
3.2.3. Soot and Metal Particles
3.2.3.1. Soot
3.2.3.2. Metal Particles
3.2.4. Contrail and Ice Particle Formation
3.2.4.1. Formation Conditions
and Observations
3.2.4.2. Freezing of Contrail Particles
3.3. Regional and Global-Scale Impact of Aviation on
Aerosols
3.3.1. Global Aircraft Emissions and Aerosol Sources
3.3.2. Sulfate Aerosol
3.3.2.1. Stratosphere
3.3.2.2. Troposphere
3.3.2.3. Differences between
the Upper Troposphere and Lower Stratosphere
3.3.3. Observations of Aviation-Produced Aerosol and
Sulfate Aerosol Changes
3.3.4. Modeling Sulfate Aerosol Perturbations Caused
by Aircraft
3.3.4.1. Subsonic Aircraft
3.3.4.2. Supersonic Aircraft
3.3.5. Soot
3.3.6. Polar Stratospheric Clouds and Aircraft Emissions
3.4. Contrail Occurrence and Persistence and Impact
of Aircraft Exhaust on Cirrus
3.4.1. Cirrus and Contrails
3.4.2. Cirrus and Contrail Models
3.4.3. Contrail Occurrence
3.4.4. Contrail Properties
3.4.5. Impact of Aircraft Exhaust on Cirrus Clouds and
Related Properties
3.5. Long-Term Changes in Observed Cloudiness and Cloud-Related
Parameters
3.5.1. Changes in the Occurrence and Cover of Cirrus
Clouds
3.5.1.1. Surface Observations
3.5.1.2. ISCCP Observations
3.5.1.3. HIRS Observations
3.5.1.4. SAGE Observations
3.5.1.5. Upper Bound for Aviation-Induced
Changes in Cirrus Clouds
3.5.2. Changes in Other Climate Parameters
3.5.2.1. Sunshine Duration
and Surface Radiation
3.5.2.2. Temperature
3.5.3. Limitations in Observed Climate Changes
3.6. Radiative Properties of Aerosols, Contrails, and
Cirrus Clouds
3.6.1. Direct Radiative Impact of Aerosols
3.6.2. Radiative Properties of Cirrus Clouds
3.6.3. Radiative Properties of Contrail Clouds
3.6.4. Radiative Forcing of Line-Shaped Contrail Cirrus
3.6.5. Radiative Impact of Additional or Changed Cirrus
and Other Indirect Cloud Effects
3.7. Parameters of Future Changes in Aircraft-Produced
Aerosol and Cloudiness
3.7.1. Changes in Climate Parameters
3.7.2. Changes in Subsonic Aircraft
3.7.3. Expected Changes for Supersonic Aircraft
3.7.4. Mitigation Options
References
DAVID W. FAHEY AND ULRICH SCHUMANN
Lead Authors:
S. Ackerman, P. Artaxo, O. Boucher, M.Y. Danilin, B. Kärcher, P. Minnis,
T. Nakajima, O.B. Toon
Contributors:
J.K. Ayers, T.K. Berntsen, P.S. Connell, F.J. Dentener, D.R. Doelling,
A. Döpelheuer, E.L. Fleming, K. Gierens, C.H. Jackman, H. Jäger, E.J. Jensen,
G.S. Kent, I. Köhler, R. Meerkötter, J.E. Penner, G. Pitari, M.J. Prather,
J. Ström, Y. Tsushima, C.J. Weaver, D.K. Weisenstein
Review Editor:
K.-N. Liou
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