Aerosol Impacts on the
Land-Atmosphere Interactions
Significance and Challenge
Atmospheric aerosols are a mixture of solid and/or
liquid particles in the air, which are ubiquitous and often observable as smoke, dust, and haze
[see some satellite images from NASA’s Visible Earth below]. These tiny
particles can have a variety of important impacts on the environment. Sulfate,
nitrate, and some other ions in the aerosols are a major source of acid
precipitation. In addition, fine particles may have a significant detrimental
effect on human health. This concern has led to proposals to reduce
concentration of fine particles by emissions control. The atmospheric
deposition of mineral dust containing iron may alter the marine biological
activity.
Through their scattering and absorption of radiation
(so-called direct effect), aerosols
can also induce some other important environment effects. For example, aerosols
are a major contributor to visibility problem in urban centers as well as rural
areas. Closely related to the visibility problem is the scattering and
absorption of solar UV by aerosols that can have significant impacts on both
the DNA damaging UV radiation reaching the surface [Liu et al., 1991] and 
photochemistry in the boundary layer [Dickerson et al., 1997]. Aerosols can
also have significant impacts on the ecological system [Chameides et al., 1999]. Finally and
probably most importantly, tropospheric aerosols are
believed to play a significant role in the earth's energy budget and climate
through the direct effect [Coakley et al., 1983; Charlson et
al., 1992; Penner et al., 1992] as well as
altering cloud microphysical and optical properties (so-called indirect effect) [Twomey, 1977; Albrecht, 1989]. The radiative forcing of anthropogenic aerosols may be
comparable to that of greenhouse gases but with the opposite sign [IPCC, 2001].
In the past two
decades, considerable research efforts and significant scientific progress have
been made. On the other hand, large uncertainties exist in the current
estimates of aerosol forcing because of incomplete knowledge concerning the
physical and chemical properties of the aerosols, their global/regional
distributions, and the aerosol-cloud interactions. Even less studied is how the
atmosphere responds to the aerosol radiative
perturbations at the surface and in the atmosphere, which should depend on land
cover and large-scale motion (e.g., mid-latitude subsidence vs. tropical ascending).
Quantification of potential impacts of aerosols on ecological system and
biogenic emissions remains challenging.
Research Topics and Approaches
Aerosol research in
our group dates back to more than ten years ago. In 1992, Prof. Dickinson
coauthored a Science paper with
Profs. Penner and O’Neill that estimates effects of
biomass burning aerosol on global radiation budget. Currently under the
auspices of NSF, DOE, and NASA, the group is
addressing several outstanding scientific questions on both regional and global
scale, by using satellite remote sensing of aerosols, land surface properties,
cloud and precipitation (e.g., MODIS, TOMS, TRMM, CERES, ISCCP, etc.), and
conducting both one-dimensional (1-D) and three-dimensional (3-D) modeling of
atmosphere-land interactions. Some activities are conducted in collaboration
with Prof. Fu’s and Prof. Chameides’ groups. Specifically, our current research
topics include:
Characterization of
regional/global aerosol distributions using the assimilation approach
Quantification of aerosol solar
radiative forcing and its impacts on the biosphere
Exploration of aerosol impacts
on the land-atmosphere interactions and climate
Related
Publications
Yu, Hongbin, R.E. Dickinson, M. Chin, Y.J. Kaufman, M. Zhou, L.
Zhou, Y. Tian, O. Dubovik,
and B.N. Holben (2004), The direct radiative
effect of aerosols as determined from a combination of MODIS retrievals and
GOCART simulations, J. Geophys. Res., 109,
D03206, doi:10.1029/2003JD003914. reprint (pdf) [Copyright
2003 American Geophysical
Yu, Hongbin, R.E. Dickinson, M.
Chin, Y.J. Kaufman, B.N. Holben, I.V. Geogdzhayev, and M.I. Mishchenko:
Annual cycle of global distributions of aerosol optical depth from integration
of MODIS retrievals and GOCART model simulations.
Journal of Geophysical Research, 108
(D3), 4128, doi:10.1029/2002JD002717, 2003. reprint (pdf), color figures (ps files)
[Copyright 2003 American Geophysical
Yu,
Liu, Y.Q., S.C. Liu, R.E.
Dickinson: Regional response of atmospheric circulation and surface energy and
water balance to observed distribution of aerosol loading over the
Yu, Hongbin, Radiative Effects of Aerosols on the Environment in China, Ph.D. Dessertation, 226pp, School of Earth and Atmospheric
Sciences, Georgia Institute of Technology, July 2000.
Chameides W.L., H. Yu, S.C. Liu, M. Bergin, X. Zhou,
L. Mearns, W. Gao,
C.S. Kiang, R. Saylor, Chao Luo,
Yan Huang, A. Steiner, and F. Giorgi:
A case study of the effect of atmospheric aerosols and regional haze on
agriculture: An opportunity to enhance crop yields in
Penner, J.E., R. E. Dickinson, C.A.
O'Neill: Effects of aerosol from biomass burning on the global radiation
budget, Science, 256, 1432-1434, 1992.
Presentations
Yu, Hongbin, Yan Zhang, R.E. Dickinson, Rong
Fu, Simulations of smoke-land-atmosphere interactions over forest and pasture,
AGU 2003 Fall meeting, San Francisco, December 8-12, 2003.
Zhou, Mi, Hongbin
Yu, and R.E. Dickinson: Application of MODIS land albedo
to estimate of aerosol direct radiative forcing,
Solar Radiation and Climate Gordon Conference,
Yu, Hongbin: Impacts of aerosols
on the land-air interactions. NASA Goddard Space Flight Center, AEROCENTER,
Greenbelt, Maryland, March 20, 2002.
Yu,
Sponsors
Office
of Science (Biological and Environment Research), the
Atmospheric
Science Division, the
AEROCENTER
Visiting Scientist Program, National
Aeronautics and Space Administration (NASA)