Professor of Physics and Atmospheric Science
Diploma (1967), Charles University, Prague
Ph.D. (1970), University of California, Riverside
Member of the Americal Meteorological Society, American Geophysical
Union, Canadian Meteorological and Oceanographic Society, Fellow
of the Optical Society of America
My research interests
- Atmospheric Radiation
- Atmospheric Aerosols
- Cloud Physics
- Ice Core Analysis
- Climate Diagnostic
- Global Change
My research group
- Petr Chylek
- I Wayan Sudiarta (Ph. D. student)
- Xiaobo Chen (Ph. D. student)
- Dr. Glen Lesins (Research Associate)
- Dr. W. Kim (Postdoctoral Fellow)
- Regina Mass (Lab Technician)
- Nancy Ogden (Lab Technician)
Current Research Projects
A common view on the current climate change (global warming)
is that it is a result of fossil fuel burning and the following
increase in atmospheric concentration of carbon dioxide. In reality
there are several factors that produce the current climate change.
Some of the most important are:
- natural climate variability
- variability of the incoming solar radiation
- increrase in atmospheric concentration of carbon dioxide
- increase in atmospheric concentration of other greenhouse
gases, especially methane
The goal of our research is to understand the relative contributions
of the above listed factors to the currently observed global warming.
For this purpose we are analyzing existing climate and paleoclimate
data, analyzing outputs of general circulation models and creating
new approximations to for the various physical processes involved
in climate system.To bring together experts holding different
views on the current global warming an to faciliate an intense
discussion of the related scince, we are organizing The First
International Conference on Global Warming and The Next Ice Age,
sponsorod by the American Meteorological Society and by the Canadian
Meteorological and Oceanographic Society, to take place in Halifax
in August 2001.
Atmospheric aerosols (airborne particulate matter) play an
important role in atmospheric energy balance and climate change.
Aerosols also affect biogeochemical cycles and human health. Man-made
aerosols include sulfates, nitrates, black carbon, products of
biomass burning, and soil dust (produced by agricultural activities).
Main types of natural aerosols are sea salt, soil dust, aerosols
produced by volcanos and forest fires, and biogenic sulfates and
organic aerosols. Aerosols affect climate through their direct
interaction with solar and terrestrial radiation (direct aerosol
effect) and through their effect on the optical properties and
life cycle of clouds (indirect aerosol effect). Atmospheric aerosols
can significantly modify the predicted warming of greenhouse gases.
We are investigating the growth of aerosols (sulfates, nitrates,
sea salt, mineral dust and black carbon) with relative humidity,
their interaction with atmospheric radiation, and their effect
on clouds and climate. Our work also include the parameterization
of aerosol optical properties as functions of relative humidity
for use in climate models.
Clouds reflect a considerable portion of incoming solar radiation
back to space and they modify outgoing infrared radiation. The
interplay between atmospheric radiation and dynamics, cloud microphysics,
aerosols, and thermodynamics is not fully understood. In many
cases, predicted climate changes (connected to increasing concentration
of carbon dioxide and other greenhouse gases) are dependent on
the cloud parameterization used in a particular general circulation
model. Our current research concerns the effect of atmospheric
aerosols on cloudiness and cloud optical properties, and improvement
of cloud parameterizations in radiation codes used in climate
models. We are also investigating the effect of black carbon on
the absorption of solar radiation by clouds.
Laboratory and Field Measurements
In recent years we have seen tremendous progress in computer-based
modeling of various atmospheric processes. Laboratory and field
measurements are needed to provide suitable checks of our modeling
abilities. The discrepancy between the measured and calculated
absorption of solar radiation in cloudy atmospheres demonstrates
the need of a balanced approach to atmospheric research that includes
modeling and measurements. In our laboratory we are currently
performing the most accurate measurements of the refractive indices
of water, supercooled water, ice, sulfates, and nitrates. Our
graduate students have participated in several international field
measurement programs like NARE (North Atlantic Regional Experiment),
RACE (Radiation, Aerosols and Cloud Experiment) and FIRE.
Ice Core Analysis
Ice core contains a wealth of information concerning past climate.
We have developed a method for determining black carbon (soot)
concentrations in ice core samples and we were able to detect
large forest fires that occured up to about 2000 years ago. We
also observed a large increase in biosphere burning (recorded
in Antarctic ice core samples) a few thousand years after the
end of the last ice age. Our current investigation is directed
towards recent changes (last 200 years) in black carbon deposition
rates in polar regions, attributed possibly to anthropogenic activities.
Light Scattering and Radiative Transfer
We are using several computational techniques and approximations
to calculate the scattering and absorption of radiation by nonspherical
and composite atmospheric particles. Ice crystals and mineral
dust aerosols are examples of nonspherical particles in the atmosphere.
Hailstones, melting snow, and mineral dust or black carbon within
sulfate or cloud droplets are common composite particles. The
scattering and absorption characteristics of these particles are
needed for remote sensing and for climate forcing calculations.
Monte Carlo and other radiative transfer techniques are used to
determine aerosol climate forcing, and the effect of clouds and
aerosols on surface UV fluxes. We are trying to understand interactions
between solar and terrestrial radiation, and clouds, aerosols,
and climate. The tools used in our research include laboratory
and field measurements, computational modeling, and theoretical
Recently Supervised Ph. D. Thesis
Recently Supervised M. Sc. Thesis
Recent Invited Presentations
- Balck Carbon and Absorption of Solar Radiation by Clouds
and Aerosols, Seminar, Desert Research Institute, University
of Nevada, Reno, April, 1997.
- Absorption of Solar Radiation by Water Vapor Dimers,
Seminar at the National Center of Atmospheric Research, Boulder,
- Black Carbon in the Atmosphere, Invited
presentation at the AGU Spring Meeting, Baltimore, June 1997.
- Black Carbon, Water Vapor Dimers and Absorption of
Solar Radoation in the Atmosphere, Seminar, Los Alamos
National Laboratory, Los Alamos, NM.
- Possible Causes of Atmospheric Excess Absorption,
Invited presentation at the Gordon Research Conference
on Solar Radiation and Climate, Plymouth, NH, June 1998.
- Heterogeneous Particles and Effective Medium Approximations,
Invited presentation at the Conference on Light Scattering
by Nonspherical Particles: Theory, Measurements and Applications,
Goddard Institute for Space Studies, New York, Oct. 1998.
- Ice Cores and Mineral Dust Aerosol, Invited
presentation at the International Workshop on Mineral Dust, Boulder,
June 8-10, 1999.
- Global Warming and the Next Ice Age, Seminar,
Environmental Research Laboratory, NOAA, Boulder, January 2000.
- Memorial Lecture in Honor of Prof. Hendrick Van deHulst,
Fifth International Conference of Light Scattering by Nonspherical
Particles, 28 August - 1 September, 2000, Halifax, Nova Scotia,
- North Atlantic Oscillations, Global Warming and The
Greenland Ice Sheet, Seminar, Air Resources Laboratory,
NOAA, Boulder, October 2000.
Recent Publications (1995-2000)
- P. Chylek, G. Lesins and U. Lohmann, Enhancement
of dust source area during past glacial periods due to changes
in the Hadley circulation, J. Geophys. Res.,
2000, in press.
- S. Dobbie, J. Li, R. Harvey and P. Chylek,
Sea salt optical property parameterization and GCM forcing
at solar wavelengths, Atmos. Res.,2000, in press.
- J. Li, S. Dobbie and P. Chylek, Parameterization
of the optical properties and growth of sulfate aerosol,
J. Atmos. Sci., 2000, in press.
- I.W. Sudiarta and P. Chylek, Absorption
and scattering cross sections of spherical particles in absorbing
medium, J. Opt. Soc. Am.,2000, in press.
- P. Chylek, G. Jennings and R. Pinnick, Soot,
In: Encyclopedia of Atmospheric Science, Academic,
2000, in press.
- I.W. Sudiarta and P. Chylek, Mie scattering
efficiency of a large spherical particle embedded in an absorbing
medium J. Opt. Soc. Am.,2000, in press.
- W. Geldart and P. Chylek, Absorption
of solar raiation by charged water droplets J. Quant.
Chem. Rad. Trans., 2000, in press.
- P. Chylek, G. Videen, W. Geldart, S. Dobbie, and
W. Tso, Effective Medium Approximation for Heterogeneous
Particles, In Light Scattering by Nonspherical Particles:
Theory, Measurements, and Geophysical Applications, 273-308,
M. Mishchenko, Editor, Academic, 2000.
- P. Chylek, Q. Fu, W. Tso and W. Geldart,
Contribution of water vapor dimers to clear sky absorption
of solar radiation, Tellus 51A, 304-313,
- P. Chylek, L. Kou, B. Johnson, F. Boudala and G.
Lesins, Black carbon concentrations in precipitation
and near surface air in and near Halifax, Nova Scotia, Atmos.
Environ. 33, 2269-2277, 1999.
- J. S. Dobbie, J. Li and P. Chylek, Two
and Four Stream Optical Properties for Water Clouds and Solar
Wavelengths J. Geophys. Res., 410 2067-2079,
- O. Boucher, S. E. Schwartz, T. P. Ackerman, B. Bergstrom,
B. Bonnel, P. Chylek, A. Dahlback, Y. Fouquart, Q. Fu, R. Halthorne,
T. Iversen, J. Haywood, S. Kato, S. Kinne, A. Kirkevag, K. Knapp,
A. Lacis, I. Laszlo, S. Nemesure, V. Ramaswamy, D. Roberts, P.
Russell, M. Schlesinger, G. Stephens, R. Wagener, M. Wang, J.
Wong, and F. Yang, Intercomparison of models representing
direct shortwave radiative forcing by sulfate aerosols, J.
Geophys. Res., 103,16979-16998, 1998.
- P. Chylek and J. Wong Erroneous
use of modified Kohler equation in cloud and aerosol physics
applications, J. Atmos. Sci., 55, 1473-1477,
- W. Tso, W. Geldart and P. Chylek, Anharmonicity
and cross section for absorption of radiation by water dimers,
J. Chem. Phys., 108, 5319-5329, 1998.
- P. Chylek, L. Kou, B. Johnson, F. Boudala and G.
Lesins, Black carbon
concentrations in precipitation and near surface air in and near
Halifax, Nova Scotia, Atmos. Environ.,1998,
- Q. Fu, G. Lesins, J. Higgins, T. P. Charlock, P.
Chylek and J. Michalsky, Water vapor continuum absorption
of solar radiation tested using ARM data, Geophys.
Res. Lett., 25, 1169-1172, 1998.
- P. Chylek and J. Wong, Cloud
radiative forcing ratio: an analytical model, Tellus
,50A, 259-264, 1998.
- P. Chylek and G. Videen, Scattering
by a composite sphere and effective medium approximations,
Opt. Comm., 146, 15-20, 1998.
- P. Chylek and G. Videen, Effect of air
bubbles on the absorption of solar radiation by cloud droplets,
J. Atmos. Sci., 55, 340-343, 1998.
- G. Videen and P. Chylek, Limits of the
anomalous diffraction approximation, Atm. Res.,
49, 77-80, 1998.
- P. Chylek and W. Geldart, Water vapor dimers
and atmospheric absorption of electromagnetic radiation ,
Geophys. Res. Lett., 24, 2015-2018, 1997.
- B. Winter and P. Chylek, Contribution
of sea salt aerosol to the planetary clear-sky albedo, Tellus
, 49B , 72-79.
- S. Gosse, M. Wang, D. Labrie and P. Chylek,
Imaginary part of refractive index of sulfates and nitrates
in the 0.7-2.6 micron spectral region, Appl. Opt. ,
36 , 3622-3634, 1996.
- S. Gosse, D. Labrie and P. Chylek, Refractive
index of ice in the 1.4 to 7.8 micron spectral range, Appl.
Opt. , 34 , 6582-6586, 1996.
- P. Chylek, G. Lesins,G. Videen, J. Wong, R. Pinnick
D. Ngo and J. Klett, Black carbon and absorption of solar
radiation by clouds, J. Geophys. Res., 101,
23365-23371, 1996. (/li>
- P. Chylek, C. Banic, P. Damiano, G. Isaac, B. Johnson,
R. Leaitch, P. Liu, D. Ngo, F. Said and B. Winter, Black Carbon:
Atmospheric Concentrations and Cloud Water Content Measurements
over Southern Nova Scotia, J. Geophys. Res.,
101, 29105-29110, 1996.
- S. Hill and P. Chylek, Comment on A Rigorous
Explanation for the Resonances Observed in the Scattering from
Spherical Ice Particles, IEEE Trans, Antennas and Propagat.,
44, 1052-1055, 1996.
- P. Chylek, B. Johnson, P. Damiano, K. Taylor and
P. Clement, Biomass Burning and Black Carbon in
the GISP2 Ice Core, Geophys. Res. Lett. , 22
, 89-92, 1995.
- P. Chylek and J. Wong, Effect
of Absorbing Aerosol on Global radiation Budget, Geophys.
Res. Lett. , 22 , 929-931, 1995.
- P. Chylek, G. Videen, D. Ngo, R. Pinnick, and J.
Klett, Effect of black carbon on the optical properties
and climate forcing of sulfate aerosols, J. Geophys.
Res., 100, 16325-16332,1995.
- P. Chylek and J. Li, Light Scattering
by Small Particles in an Intermediate Region, Optics
Communications, 117, 389-394,1995.
- G. Videen, J. Li and P. Chylek, Resonances
and Poles of Weakly Absorbing Spheres, J. Opt. Soc.
Am., A12, 916-921, 1995
- G. Videen, D. Ngo, P. Chylek and R. Pinnick,
Light scattering from a sphere with an irregular inclusion,
J. Opt. Soc. Am., A12, 922-928, 1995
- P. Chylek and J. Dobbie, Inhomogeneous
Cirrus Clouds: Monte Carlo Simulation, J. Atmos. Sci.,
52 3512-3522, 1995.
- P. Chylek and J. Wong, Effect of Absorbing
Aerosols on Global Radiation Budget, Geophys. Res.
Lett., 22, 929-931, 1995.
- J. Li, W. Geldart and P. Chylek, Second
Order Perturbation Solution For Radiative Transfer in Clouds,
J. Quant. Spectr. Radiat. Transfer., 53,
- P. Chylek, P. Damiano, N. Kalyaniwalla and E. Shettle,
Radiative Properties of Water Clouds, Atm. Res.,
35, 139-156, 1995.
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