Aerosol in Global Atmosphere
Colin O’Dowd
School of Physics and Centre for Climate and Air
Pollution Studies, Ryan Institute, National
University of Ireland Galway, Galway, Ireland
Article Outline
Glossary
Definition of the Subject
Introduction: The Nature and Impacts of
Atmospheric Aerosols
Aerosol Formation, Dimensions, and Removal
Global Aerosol Budgets, Burdens, and Spatial
Distributions
Water Uptake by Aerosols
Aerosols, Global Radiative Budget, Precipitation,
and Climate
Aerosols and Air Pollution
Future Directions: Interactions Between Aerosol
Air Pollution and Climate
Bibliography
Glossary
Aerosol optical depth Quantitative measure of
the extinction of solar radiation by aerosol
scattering and absorption between the point of
observation and the top of the atmosphere.
Aerosol A suspension of liquid or solid particles
in a fluid (in this context air). Also referred to
as particulate matter (PM).
Climate Mean values of meteorological parameters in a given region over relatively long
periods of time.
Cloud droplet activation Spontaneous condensation growth of a wettable aerosol particle into
a cloud droplet.
Homogeneous nucleation Spontaneous formation of an aerosol particle from vapor phase
precursors through a phase transition, without
need of a particle nucleus.
Hygroscopicity The ability to absorb water from
the atmosphere.
Radiative forcing The radiative forcing of the
surface-troposphere system due to the perturbation in or the introduction of an agent (say, a
change in greenhouse gas concentration) is
defined as the change in net (down minus up)
irradiance (solar plus longwave in Wm
À2 ) at
the tropopause.
Definition of the Subject
Atmospheric aerosols are airborne liquid or solid
particles, varying in size from nanometers to hundreds of microns. Atmospheric aerosols are formed
from both natural and anthropogenic sources and
can have complex chemical speciation and shape.
They are formed from mechanical breakup of a
parent material, such as dust or sea spray
(so-called primary aerosol formation), or from
gas-to-particle conversion processes, such as condensation of semivolatile organic compounds
(VOCS) or chemical reactions in the aerosol
phase such as oxidation of SO 2 to SO 4 (so-called
secondary aerosol formation). These tiny airborne
particles can form haze and cloud layers that influence the Earth’s climate: aerosols directly reflect
incoming solar radiation back out to space, providing a direct radiative effect on climate, some of
which act as cloud condensation nuclei in the
cloud formation process where they determine
cloud microphysical and radiative properties, ultimately determining cloud reflectance providing an
indirect radiative effect. The net climatic impact of
atmospheric aerosols is to provide a cooling effect
that partially offsets greenhouse gas-induced
global warming. Aerosols also contribute to poor
air quality and adverse health effects, typically
resulting in reduced life span and increased mortality rates in the most polluted environments.
© Springer Science+Business Media, LLC 2012
M. E. Goodsite et al. (eds.), Air Pollution Sources, Statistics and Health Effects,
https://doi.org/10.1007/978-1-0716-0596-7_322
Originally published in
R. A. Meyers (ed.), Encyclopedia of Sustainability Science and Technology, © Springer Science+Business Media LLC, 2012
https://doi.org/10.1007/978-1-4419-0851-3_322
239
Colin O’Dowd
School of Physics and Centre for Climate and Air
Pollution Studies, Ryan Institute, National
University of Ireland Galway, Galway, Ireland
Article Outline
Glossary
Definition of the Subject
Introduction: The Nature and Impacts of
Atmospheric Aerosols
Aerosol Formation, Dimensions, and Removal
Global Aerosol Budgets, Burdens, and Spatial
Distributions
Water Uptake by Aerosols
Aerosols, Global Radiative Budget, Precipitation,
and Climate
Aerosols and Air Pollution
Future Directions: Interactions Between Aerosol
Air Pollution and Climate
Bibliography
Glossary
Aerosol optical depth Quantitative measure of
the extinction of solar radiation by aerosol
scattering and absorption between the point of
observation and the top of the atmosphere.
Aerosol A suspension of liquid or solid particles
in a fluid (in this context air). Also referred to
as particulate matter (PM).
Climate Mean values of meteorological parameters in a given region over relatively long
periods of time.
Cloud droplet activation Spontaneous condensation growth of a wettable aerosol particle into
a cloud droplet.
Homogeneous nucleation Spontaneous formation of an aerosol particle from vapor phase
precursors through a phase transition, without
need of a particle nucleus.
Hygroscopicity The ability to absorb water from
the atmosphere.
Radiative forcing The radiative forcing of the
surface-troposphere system due to the perturbation in or the introduction of an agent (say, a
change in greenhouse gas concentration) is
defined as the change in net (down minus up)
irradiance (solar plus longwave in Wm
À2 ) at
the tropopause.
Definition of the Subject
Atmospheric aerosols are airborne liquid or solid
particles, varying in size from nanometers to hundreds of microns. Atmospheric aerosols are formed
from both natural and anthropogenic sources and
can have complex chemical speciation and shape.
They are formed from mechanical breakup of a
parent material, such as dust or sea spray
(so-called primary aerosol formation), or from
gas-to-particle conversion processes, such as condensation of semivolatile organic compounds
(VOCS) or chemical reactions in the aerosol
phase such as oxidation of SO 2 to SO 4 (so-called
secondary aerosol formation). These tiny airborne
particles can form haze and cloud layers that influence the Earth’s climate: aerosols directly reflect
incoming solar radiation back out to space, providing a direct radiative effect on climate, some of
which act as cloud condensation nuclei in the
cloud formation process where they determine
cloud microphysical and radiative properties, ultimately determining cloud reflectance providing an
indirect radiative effect. The net climatic impact of
atmospheric aerosols is to provide a cooling effect
that partially offsets greenhouse gas-induced
global warming. Aerosols also contribute to poor
air quality and adverse health effects, typically
resulting in reduced life span and increased mortality rates in the most polluted environments.
© Springer Science+Business Media, LLC 2012
M. E. Goodsite et al. (eds.), Air Pollution Sources, Statistics and Health Effects,
https://doi.org/10.1007/978-1-0716-0596-7_322
Originally published in
R. A. Meyers (ed.), Encyclopedia of Sustainability Science and Technology, © Springer Science+Business Media LLC, 2012
https://doi.org/10.1007/978-1-4419-0851-3_322
239