Global Aerosols: Distribution of Dust, Smoke and Haze Based on Surface and Satellite Observations or Atmospheric Aerosols as Indicators of Global Biogeochemical Changes

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Global AerosolsDistribution of Dust, Smoke and
Haze Based onSurface and Satellite
ObservationsorAtmospheric Aerosols as
Indicators of Global Biogeochemical Changes
Rudolf Husar
CAPITA, Washington University http//capita.wustl.
edu/CAPITA/CapitaReports/MTAEloadas/NASALangley/NA
SALanagley/
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The Living, Changing Earth
The physical, chemical and biological state of
the Earths environment is constantly changing
due to aging, evolution and human influences.
Some of the changes occur slowly in a steady
fashion and they are foreseeable. However, many
bio-geochemical changes occur quickly,
unexpectedly, and they unevenly distributed in
space and time, sometimes causing catastrophic
events.
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Earth Science Explaining the Change
The basic elements of life including carbon,
nitrogen, phosphorus, calcium are in constant
circulation between the earths major
environmental compartments atmosphere,
hydrosphere, lithosphere, and biosphere.
Changes will occur if the circulation of the
substances is perturbed, e.g. the CO2 has
increased because the rate of carbon input is
larger than the rate of output from the
atmosphere.
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Sensory-Motor Response to Changes
The inevitable and unforeseeable environmental
changes require response to these changes
consisting of three steps
Sensing and recognition (monitoring)
Reasoning and explaining (sciences)
Decision making, action (management)

All living organisms use this type of
sensory-motor feedback to maintain their
existence (sustainable development).
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Aerosols as Indicators of Global Biogeochemical
Changes

• Aerosols are suitable indicators of dust
  movement, fire and smoke, volcanic emissions and
  anthropogenic fossil fuel combustion.
• Each source type has a unique signiture either in
  size distribution, chemical composition, or
  optical properties.
• Aerosols can be easily detected because they
  effectively scatter visible light from the sun.
• Space and surface-based monitoring systems
  already exist to monitor the daily aerosol
  pattern globally.

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Major Biogeochemical Processes That Produce
Aerosols
Dust storms
Fires
Volcanoes
Anthropogenic pollution
These processes are producing visible aerosols in
form of dust, smoke, and haze. The quantity and
spatial-temporal distribution of dust and smoke
and haze can be used to characterize the flow of
substances through the atmosphere.
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Just like the human eye, satellite sensors detect
the total amount of solar radiation that is
reflected from the earths surface (Ro) and
backscattered by the atmosphere from pure air,
clouds and aerosols.
Satellite Detection of Aerosols
Today, geo-synchronous and polar orbiting
satellites can detect different aspects of
aerosols over the globe daily.
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A simplified expression for the relative
radiatioin detected by a satellite sensor (I/Io)
is
Satellite Detection of Aerosols
I / Io Ro e-? (1- e-?) P
where ? is the aerosol optical thickness and P
the angular light scattering probability.
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Dust Storms
Dust storms transport Aeolian dust from one part
of the Earth to another. Loess, the fertile silty
yellowish brown soil, covers about 10 of the
land surface of the Earth. In China, for example,
100 meter deep layers of loess are found.
The source areas of loess are the hot and
temperate deserts. The dust particles are
removed from the surface of sand dunes by the
force of the wind. The chemical composition of
the dust is similar to the composition of the
sand.
The smaller dust particles in the size range 1-5
mm are transported several thousand kilometers
from their source. Sahara dust can be found in
South America and East Asian dust over North
America and Greenland.
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Sahara Dust Over West Africa
Monitoring the atmospheric dust concentration and
flow allows the estimation of the dust transport,
drought conditions, desertification and other
changes over arid regions.
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The Asian Dust Event of April 1998
On April 15th, 1998 an unusually intense dust
storm began in the western China, just in time
for the east Asian dust season. CNN reported
that 12 people were missing in the storm. By the
April 20th, the elongated dust cloud covered a
1000 mile stretch of the east coast of China.
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The 1998 Asian Dust and the Central American
Smoke Events

• In the spring of 1998 two major tropospheric
  aerosol events occurred that illustrate the
  global/continental-scale transport, as well as
• The utility of satellites to detect and to track
  the aerosol clouds
• The support of the scientific community to aid
  the air quality management on short notice.

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Transport over Pacific
The dust cloud was traversing Pacific in five
days. It appeared as a yellow dye on color
SeaWiFS satellite images visualizing its own path
across the Pacific.
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Impact of Asian Dust on North America
By April 27th, the dust cloud rolled into North
America. Satellite images show that one branch
of the dust plume was heading southward along the
California coast and another branch continued
eastward across the Canadian Rockies.
During the dust event the PM10 and PM2.5
concentrations in Washington state reached 120
and 40 mg/m3, respectively.
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Science Support to Air Quality Management

• A few scientists were monitoring Asian dust
  event.
• As the Asian dust approached the Pacific Coast of
  North America, air quality managers and other
  scientists were alerted.
• Within two days, over 40 scientists and managers
  have reported their observations and preliminary
  data on the web.
• The air quality managers used the science website
  to inform the public.

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Fires
Vegetation fires are important to the ecology of
many terrestrial systems because they cycle many
trace elements. Fires are also major sources of
atmospheric trace gases and aerosols. Nowadays
vegetation fires are initiated mostly by humans
for land clearing, agricultural harvest clearing,
savanna burning for nomadic agriculture. Over the
sub-Sahara savanna region has thousands of small
fires every year in the December-February season.
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Smoke from Biomass Burning
The monitoring of smoke aerosol from forest,
grass, and agricultural fires can reveal the
location, magnitude, and seasonality of biomass
burning.
The fires produce a thick and rather uniform
smoke layer of several thousand kilometer size.
The prevailing wind transport the smoke across
the Atlantic Ocean to South America.
Occasionally, the savanna smoke and the Sahara
dust clouds overlap. The main atmospheric
removal mechanism of the smoke, dust, and haze
is through clouds and precipitation.
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Forest Fires over Central America
Throughout the spring of 1998, thousands of fires
in Central America have been burning with twice
the intensity of normal springtime fires.
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Smoke from the Central American Fires
Thick smoke has been lingering over southern
Mexico, Guatemala and Honduras and adjacent
oceans throughout the spring season.
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Smoke passes over Eastern North America

• On May 12, a remarkably thick pall of smoke has
  accumulated over the entire Gulf of Mexico and
  begun a swift journey to the north along the
  Mississippi Valley. By May 15, the smoke pall had
  stretched out from Central America Hudson Bay.
  Over the next two days the smoke pall was
  literally shoved eastward by an approaching cold
  front, resulting in a remarkable contrast of
  haziness (smokiness) in the front and behind the
  front. On May 17, virtually the entire Eastern
  Seaboard was blanketed by a pall of smoke.

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SeaWiFS View of the Smoke

• GOES 8 View of the Smoke

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A füstfelho hatása US-ban

• A füstfelho útjában mindehol a megengedett érték
  feletti aeroszol koncentrációt okozott, és a
  levego homályossága gátolta a légiforgalmat

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Science - Management Interaction Regarding the
Central American Smoke Event

• The Central American fires have been keenly
  monitored by broad scientific community using
  multiple satellite sensors.
• The available on-line data were catalogued and
  summarized on the web.
• The local air quality data along with regional
  summaries were used by air quality managers to
  issue health advisories.
• The regional summaries were used by the federal
  EPA to grant the states exemptions from air
  quality standard violations.
• The Asian dust and the Central American smoke
  event has clearly demonstrated that the available
  current space-based aerosol monitoring data can
  enable virtual communities of scientists and
  managers to detect and follow major aerosol
  events and to support air quality management
  through JITERS (Just In Time Environmentally
  Relevant Science).

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Volcanic Aerosol

• Volcanic aerosols are composed of grayish
  volcanic ash which settles out within a day or
  less.
• The lasting volcanic aerosol (0.5-1 µm) is due to
  sulfuric acid that is formed in the stratosphere
  from the emitted SO2 gas

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Volcanic emissions tend to spread out through
both the northern and southern Hemisphere and
reside in the troposphere for 1-2 years.
Volcanic events are not influenced by human
actions but they tend to mask out more subtle
changes man-induced changes.

• History of volcanic aerosol optical depth,
  1850-1900 shows sporadic events several times a
  century.
• By monitoring the pattern of volcanic aerosols
  one can determine the magnitude and spatial
  impact of volcanic events.

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The Human Peturbation
Human actions have also been altering some of the
main natural biogeochemical processes. The
enhaced intentional burning of forests has
increased the flow of biological substances over
many parts of the world. The spreading of
deserts due to desertification is also likely to
influence the flow of windblown dust.
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Anthropogenic Fuel Combustion
Since the last century human activities have
significantly influenced the Earths
biogeochemical balance. The combustion of fossil
fuels, coal, oil and gas has liberated large
quantities of carbon, sulfur, and trace metals
from its long term lithospheric reservoir and
transferred it to the atmosphere..
In North America, the per capita sulfur emission
is 1/2 kg per day. This large quantity of
mobilized sulfur not only pollutes the air, but
after deposition may acidify the soil, and may
harm the plants.
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Anthropogenic Pollution
Central Europe
India
China
Eastern U.S.
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Summary Aerosols as Biogeochemical Indicators

• Aerosols are suitable indicators of dust
  movement, fire and smoke, volcanic emissions and
  anthropogenic fossil fuel combustion.
• Each source type has a unique signiture either in
  size distribution, chemical composition, or
  optical properties.
• Aerosols can be easily detected because they
  effectively scatter visible light from the sun.
• Space-based aerosol monitoring systems already
  exist to monitor the daily aerosol pattern
  globally.
• The remaining measurement can be resolved in the
  near future.
• The Asian Dust and Central American Smoke events
  have shown that air quality management can be
  effectively aided by timely scientific support.

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GAW with GAIN
An internet-based global aerosol watch (GAW)
system could established alert the relevant
science and management communities for
interesting dust, smoke, or haze aerosol events
and to provide Just-In-Time science. The
communication could be conducted through a Global
Aerosol Information Network (GAIN) that would
connect the users and the producers of earth
science data, information and knowledge.
PRODUCERS
USERS
Biomass burning - biogeochemists
Surface obs.
GAIN Global Aerosol Information Network
Aeolian dust - geologists
Vulcanologists
Satellites
Radiative effects-Climate Change
Human obs.
Pollution monitoring- Control Offices
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Acknowledgements
Thanks to the spontaneous web-based virtual
communities on Asian dust and Central American
smoke for willingness to share raw data sets as
an example for future spontaneous collaboration
on global aerosols. This research was supported
by the U.S. Environmental Protection Agency.