Thus arises an important question: Do aircraft emit sufficient amounts of
soot to have detrimental effects and warrant emission controls?
AEROSOLS AND THEIR RADIATIVE/CLIMATIC EFFECTS: SPACE, AIR, AND GROUND MEASUREMENTS AND
Philip B. Russell and Rudolf F. Pueschel1
As a part of Science Team activities for the spacecraft sensors SAM II, Stratospheric
Aerosol and Gas Experiment (SAGE, SAGE II, and SAGE III), Ames has designed, participated
in, and analyzed measurements by aircraft, balloons, and ground-based remote sensors to
validate and complement the spacecraft measurements. Current and recent activities include
ER-2 and DC-8 campaigns to measure particle size distribution, composition, and optical
depth spectra before and after the Pinatubo eruption (in coordination with SAGE II
measurements), developing the data validation plan for the SAGE III sensor (to fly on the
Earth Observing System, EOS), and designing several autotracking sunphotometers to fly on
a variety of occupied and unoccupied aerial vehicles (UAVs) as a component of
multidisciplinary studies of aerosol climatic effects.
Contrails can evolve into extended cirrus clouds. Boucher (1999) and Fahey et
al. (1999) have shown evidences that cirrus occurrence and coverage may have
increased in regions of high air traffic compared with the rest of the globe.
Smith et al. (1998) reported the existence of nearly invisible layers of small
ice crystals, which cause absorption of infrared radiation, and could be due to
remnant contrail particles. From consideration of the spatial distribution of
cirrus trends during the last 25 years, Fahey et al. (1999) gave a range of
possible best estimates of 0 to 0.04 Wm-2 for the radiative forcing
due to aviation-induced cirrus. The available information on cirrus clouds was
deemed insufficient to determine a single best estimate or an uncertainty range
Aerosols also serve as ice nuclei although it is well recognised that there are
fewer ice nuclei than cloud condensation nuclei. It is conceivable that
anthropogenic aerosols emitted at the surface and transported to the upper
troposphere affect the formation and properties of ice clouds. Jensen and Toon
(1997) suggested that insoluble particles from the surface or soot particles
emitted by aircraft, if they serve as effective ice nuclei, can result in an
increase in the cirrus cloud coverage. Laaksonen et al. (1997) argued that
nitric acid pollution is able to cause an increase in supercooled cirrus cloud
droplet concentrations, and thereby influence climate. Such
effects, if significant at all, are not quantified at present..
(Source: ipcc.ch/pub/tar/wg1/242.htm is no longer available)
European Workshop on Aviation, Aerosols, Contrails and Cirrus Clouds
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Institut für Physik der Atmosphäre
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Institute of Atmospheric Physics
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This focussed Workshop will address
persisting uncertainties on the role of aerosols and particles from aviation and
other sources to contrails and cloud formation with impact on stratospheric
ozone and climate. The recent European and international assessments (WMO, IPCC,
ICAO) stress the urgent need to clarify these uncertainties, which limit our
ability to project the atmospheric impacts of aviation. The workshop will
provide a forum for presentation of the results of current and past EC and
national research activities in this field (including THESEO). The outcome of
the Workshop will contribute to the regulatory process within ICAO and the
Montreal Protocol. For aviation industry is also of great importance to know
which type of aircraft emissions has the largest impact on contrails and cloud
Further information: firstname.lastname@example.org
(no longer available)
Assistant Professor (Research)
College of Oceanography and Atmospheric Sciences
Oceanography Admin 104
Oregon State University
Corvallis, OR 97331-5503
Most of my OSU research is related to atmospheric aerosols and
aerosol/cloud interactions, with an emphasis on airborne measurements. I also work on a
project basis for the National Center for Atmospheric Research, coordinating the
deployment of the counterflow virtual impactor (CVI) when it is requested for an airborne
Twohy, C.H., P. Austin and R.J. Charlson, 1989: Chemical consequences of the initial
diffusional growth of cloud droplets: a clean marine case. Tellus, 41B, 51-60.
Twohy, C.H., A.D. Clarke, S.G. Warren, L.F. Radke and R.J. Charlson, 1989:
Light-absorbing material extracted from cloud droplets and its effect on cloud albedo. J.
Geophys. Res., 94, 8623-8631.
Twohy, C.H., and D. Rogers, 1993: Airflow and water drop trajectories at instrument
sampling points around the Beechcraft King Air and Lockheed Electra. J. Atmos. Oceanic
Technol., 10, 566-578.
Drdla, K., A. Tabazadeh, R.P. Turco, M.Z. Jacobson, J.E. Dye, C. Twohy and D.
Baumgardner, 1994: Analysis of the physical state of one Arctic polar stratospheric cloud
based on observations. Geophys. Res. Lett., 21, 2475-2478.
Twohy, C.H., P.A. Durkee, B.J. Huebert and R.J. Charlson, 1995: Effects of aerosol
particles on the microphysics of coastal stratiform clouds. J. Climate, 8, 773-783.
Twohy, C.H., and J.G. Hudson, 1995: Measurements of cloud condensation nucleus spectra
within maritime cumulus cloud droplets: Implications for mixing processes. J. Appl.
Meteor., 34, 815-833.
Twohy, C.H., Schanot, A.J. and W.A. Cooper, 1997: Measurement of condensed water
content in liquid and ice clouds using an airborne counterflow virtual impactor. J. Atmos.
Oceanic Tech., 14, 197-202.
Jensen, E. J., O. B. Toon, S. Kinne, G. W. Sachse, B. E. Anderson, K. R. Chan, C. H.
Twohy, B. Gandrud, A. J. Heymsfield, and R. C. Miake-Lye, 1998: Environmental conditions
required for contrail formation and persistence. J. Geophys. Res., 103, 3929-3936.
Jensen, E.J., O.B. Toon, A. Tabazadeh, G.W. Sachse, B.E. Anderson, K.R. Chan, C. Twohy,
B. Gandrud, S.M. Aulenbach, A. Heymsfield, J. Hallett, and B. Gary, 1998: Ice nucleation
processes in upper tropospheric wave-clouds observed during SUCCESS. Geophys. Res. Lett.,
Laucks, M.L., and C. H. Twohy, 1998: Size-dependent sampling efficiency of an airborne
counterflow virtual impactor. Aer. Sci. and Tech., 28, 40-61.
Twohy, C.H., 1998: Model calculations and wind tunnel testing of an isokinetic shroud
for high-speed sampling. Aer. Sci. and Tech., 28, 261-280.
Twohy, C. H., and B. Gandrud, 1998: Electron microscope analysis of residual particles
from aircraft contrails. Geophys. Res. Lett., 25, 1359-1362.
Vay, S., B.E. Anderson, G.W. Sachse, J.E. Collins, J.R. Podolske, C.H. Twohy, B.
Gandrud, K. R. Chan, S.L. Baughcum, and H.A. Wallio, 1998: DC-8-based observations of
aircraft CO, CH4, N2O, and H2O emission indices during SUCCESS. Geophys. Res. Lett., 25,
Weinheimer, A.J., T.L. Campos, J.G. Walega, F.E. Grahek, B.A. Ridley, D. Baumgardner,
C. H. Twohy, and B. Gandrud, and E.J. Jensen 1998: Uptake of NOy on wave-cloud ice
particles. Geophys. Res. Lett., 25, 1725-1728.
Charlson, R.J., C.H. Twohy and P.K. Quinn, 1988: Physical influences of altitude on the
chemical properties of clouds and of water deposited from the troposphere. In Acid
Deposition at High Altitude Sites. M.H. Unsworth and D. Fowler (eds.), Kluwer Academic
Twohy, C.H., 1991: Airborne Condensation Nucleus Counter User's Guide. Technical Note
TN-356+EDD, National Center for Atmospheric Research, 21 pp.
Twohy, C.H., and D. Rogers, 1991: Flow speed and particle trajectories around aircraft:
theory and measurements. In Technical Note TN-362+1A, National Center for Atmospheric
Research, 15 pp.
Twohy, C.H., A.D. Clarke, S.G. Warren, L.F. Radke and R.J. Charlson, 1989: Measurements
of the light-absorbing material inside cloud droplets and its effect on cloud albedo.
Symposium on the role of clouds in atmospheric chemistry and global climate, Anaheim,
American Meteorological Society, 215-220.
Twohy, C.H., B.J. Huebert, P.A. Durkee and R.J. Charlson, 1990: Droplet chemistry in
stratocumulus clouds. Conference on Cloud Physics, San Francisco, American Meteorological
Baumgardner, D., and C. Twohy, 1991: Conditional sampling of aerosol and cloud droplets
in continental and marine air masses, XX General Assembly of the IUGG, Vienna, Austria,
Twohy, C.H., and D. Rogers, 1991: Airflow effects on the distribution of water droplets
around an aircraft. Seventh Symposium on Meteorological Observations and Instrumentation,
New Orleans, American Meteorological Society, 256-260.
Twohy, C.H., P.A. Durkee, K. Nielsen and R.J. Charlson, 1991: Relationships between
aerosol particles, droplets, and satellite-measured reflectance in coastal stratiform
clouds. XX General Assembly of the IUGG, Vienna, Austria, 50.
Dye, J.E., D. Baumgardner, S. Borrmann, C. Twohy, K. Drdla, and P. Newman, 1992:
Stratospheric sulfate droplets and transition to polar stratospheric cloud particles.
presented at AGU Fall Meeting, San Francisco, American Geophysical Union.
Twohy, C.H., and T.L. Anderson, 1992: Sampling artifacts produced in aircraft aerosol
inlets by the presence of large cloud droplets. Eleventh Annual Meeting, San Francisco,
American Association for Aerosol Research, 300.
Twohy, C.H., P.A. Durkee and R.J. Charlson, 1992: Effects of aerosol particles on
droplet size distributions and satellite-measured reflectance in coastal stratiform
clouds, Abstracts, Eleventh Annual Meeting, San Francisco, American Association for
Aerosol Research, 307.
Anderson, T.L., and C.H. Twohy, 1993: Collection and exclusion of large cloud elements
with a counterflow virtual impactor. Twelfth Annual Meeting, Oak Brook, Illinois, American
Association for Aerosol Research, 36.
Radke, L.R., and C.H. Twohy, 1993: Aerosol particle production near the atmosphere's
clouds interface: sorting fact from artifact. AGU Fall Meeting, San Francisco, California
(5-10 Dec 1993), American Geophysical Union, 174.
Radke, L.R., B.W. Gandrud, J.E. Ragni, C.H. Twohy and D. Baumgardner, 1994: Aircraft
research platforms with stratospheric capability. Proc. First Intl. Airborne Remote
Sensing Conference and Exhibition, Strasbourg, France (11-15 Sept 1994), Environmental
Research Institute of Michigan, I281-I293.
Twohy, C.H., 1994: Measurement of condensed water content in clouds using an airborne
counterflow virtual impactor.Proc. Conference on Aerosols and Atmospheric Optics,
Snowbird, Utah (26-30 Sept 1994), American Geophysical Union., 534.
Twohy, C.H., A.J. Schanot, M.L. Laucks, T.L. Anderson, and R.J. Charlson, 1994:
Measurement of ice cloud properties using an airborne counterflow virtual impactor. Fourth
International Aerosol Conference, Los Angeles, California (29 Aug-2 Sept 1994), American
Association for Aerosol Research, 1045.
Twohy, C.H., 1995: Precipitation. In Gale Encyclopedia of Science, Gale Research,
Laucks, M.L., and C. H. Twohy, 1996: Size-dependent sampling efficiency of an airborne
counterflow virtual impactor. Fifteenth Annual Conference, Orlando (14-18 Oct 1996),
American Association for Aerosol Research, 233.
Litchy, M.L., S.G. Howell, A.D. Clarke, B.J. Huebert, D. Baumgardner, D. Rogers, and C.
H. Twohy, 1996: Measurements of the passing efficiency of the community aerosol inlet and
associated tubing on NCAR's C-130 aircraft. Fifteenth Annual Conference, Orlando (14-18
Oct 1996), American Association for Aerosol Research, 20.
Twohy, C.H., 1996: Model calculations and wind tunnel testing of a shroud for an
airborne counterflow virtual impactor. Fifteenth Annual Conference, Orlando (14-18 Oct
1996), American Association for Aerosol Research, 232.
Faloona, I., D. Tan, W. Brune, C. Twohy, and B. Gandrud, 1997: Measurements of OH/HO2
in and around cirrus clouds. AGU Spring Meeting, Baltimore, Maryland (27-30 May 1997),
American Geophysical Union, S86 (EOS supplement).
Jensen, E.J., O.B. Toon, A. Tabazadeh, G.W. Sachse, B.E. Anderson, K.R. Chan, C. Twohy,
and B. Gandrud, 1997, Ice nucleation processes in upper tropospheric wave-clouds observed
during SUCCESS. AGU Spring Meeting, Baltimore, Maryland (27-30 May 1997), American
Geophysical Union, S94 (EOS supplement).
Twohy, C. H., B.W. Gandrud, A.J. Heymsfield, D. Baumgardner, C. Buettner, H. Gerber, P.
DeMott, and K R. Chan, 1997: Measurements of contrail nuclei and cirrus cloud
microphysics. Invited paper. AGU Spring Meeting, Baltimore, Maryland (27-30 May 1997),
American Geophysical Union, S97 (EOS supplement).
Phone: (541) 737-5690 or (503) 472-0528
Fax: (541) 737-2540
Go to: Oregon State University's College of
Oceanography and Atmospheric Sciences
Go to: NCAR's Research Aviation Facility
- Contrails and aerosols. Fijn