Global Distribution of Aerosols based on Satellite and Surface Observations

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Global Distribution of Aerosolsbased
onSatellite and Surface Observations
Presented atCooperative Institute for Research
in the Atmosphere (CIRA) Colorado State
University of, Ft. CollinsMay 3, 2000 Rudolf
Husar CAPITA, Washington University, St.
Louis http//capita.wustl.edu/CAPITA/CapitaReports
/CIRA/CIRASeminar.htm
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Biogeochemical Processes Producing Aerosols
Urban/Industrial Aerosols
Fires
Dust storms
Volcanoes
On global scale dust, smoke, industrial haze and
occasional volcanoes dominate the aerosol pattern.
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Industrial Sulfur Emission Density

• The regional hot-spots for industrial sulfur
  emissions are in
• E. North America,
• Europe and
• E. Asia

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Satellite AVHRR optical depth data over the
oceans
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POLDER Aerosol Index (Optical Depth)
In January, the aerosol burden is highest over
West Africa, India and China.
In June, high aerosol levels occur over Central
Africa, India and China.
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Visibility is recorded at 7000 stations hourly

• NOAA NCDC Global Summary of the Day (SOD)
  Observations

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Visibility on Ships McDonald 1938
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Extinction coefficient for Asia
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SeaWiFS Satellite Image of SE Asia, Dec 1999
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Haze over China
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Extinction coefficient for Africa
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Sahara Dust Storm

• NASA Astronaut Photo

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Sahara Dust Cloud
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Extinction coefficient for South America
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Fires are Seasonal
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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Extinction coefficient for N. America
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Radiative Transfer Theory for Aerosol-Surface
Co-retrieval
The sensed radiation is decomposed into
scattering and absorption by (1) gases, (2)
aerosols as well as reflection from the (3)
surfaces and (4) clouds. Air scattering and
surface/aerosol reflectance are assumed to be
additive, disregarding multiple scattering
effects.
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Apparent Surface Reflectance, R

• The aerosol scattering and absorption has twofold
  influence on the apparent reflectance of objects
  remotely sensed from space
• It reduces surface reflectance through the
  transmittance Ta as a filter
• It adds to surface reflectance through
  backscattering airlight
• The net aerosol influence depends on the relative
  contributions of filtering and aerosol
  reflectance effects

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Apparent Surface Reflectance, R
The critical parameter whether aerosols will
increase or decrease the apparent reflectance, R,
is the ratio of aerosol angular reflectance, P,
to bi-directional surface reflectance, R0, P/ R0
Aerosols will increase the apparent surface
reflectance, R, if P/R0 lt 1. For this reason,
the reflectance of ocean and dark vegetation
increases with t. When P/R0 gt 1, aerosols will
decrease the surface reflectance. Accordingly,
the brightness of clouds is reduced by overlying
aerosols. At P R0 the reflectance is unchanged
by haze aerosols (e.g. soil and vegetation at 0.8
um).. At large t (radiation equilibrium), both
dark and bright surfaces asymptotically approach
the aerosol reflectance, P
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SeaWiFS Images and Spectra at Four Wavelengths
(Click on the Images to View)
At blue (0.412) wavelength, the haze reflectance
dominates over land surface reflectance.
At green (0.555) over land, the haze is reduced
and the vegetation reflectance is increased.
At red (0.67) wavelength over land, dark
vegetation is distinctly different from brighter
yellow-gray soil.
In the near IR (0.865) over land, the surface
reflectance is uniformly high (R0gt0.30) over both
vegetation and soil and haze is not discernable.
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Industrial Haze over the East Coast
Over the ocean with thick haze, the haze
correction removes over 90 of the signal
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Retrieved Aerosol Optical Thickness, t (Click on
the Images to View)
Aerosol optical thickness at 0.412 shows large
patches of t gt 0.5.The black areas are from the
cloud mask.

• Total reflectance due to surface, haze and
  clouds.

The Angstrom slope b of the spectral AOT (t
?-b) is sharply reduced over the misty haze
region
The t at 0.67 shows a sharply delineated area of
mist i.e. thick gray haze.
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Global Aerosol over Land and Ocean
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Major Aerosol Events

• East-Asian Dust Transport to N. America
• Central American Transport to N. America

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Figure 3. Dust transport over the Pacific Ocean
between April 21-25. In the SeaWiFS images
Kuring, 1998, the dust appears as a yellow dye
marking its own position at noon each day.
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SeaWiFS Satellite Image for April 19
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SeaWiFS Satellite Image for April 21
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Dust Cloud Over North AmericaGOES 10 S GOES 10
Geostationary satellite image
By April 27th, the dust cloud rolled into North
America and split with one branch heading
southward along the CA coast and the another
branch continuing eastward across the Canadian
Rockies.
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West Coast PM10 Concentration

• Regional average PM10 levels reached 65 µg/m3
  compared to typical values of 10-25 µg/m3
• On April 29, the PM10 exceeded 100 µg/m3 over
  parts of Washington and Oregon

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West Coast PM10 Concentration
Diurnal pattern of dust of Northern California.
a) Hourly PM10 concentration averaged over 12
stations in Northern California. b) Diurnal
pattern of PM10 on April 29, 1998. c) Location of
the hourly PM monitoring sites in northern
California.
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IMPROVE Fine Particle Dust Concentrations
April 25, 1998 April 29, 1998
May 2, 1998
On April 25, the western U.S. was virtually
dust-free, but reached high concentrations by
April 29. On May 2, the elevated dust
concentrations moved over the Rocky Mountains and
the Colorado Plateau
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Smoke from Central American Fires
May 4
May 5
May 7
May 8
May 6
Daily map of smoke aerosol (May 4-28, 1998) from
the Central American fires based on TOMS
absorbing aerosol index. (levels 12 and 27)
May 9
May 10
May 11
May 12
May 13
May 14
May 15
May 16
May 17
May 18
May 19
May 20
May 21
May 22
May 23
May 24
May 25
May 26
May 27
May 28
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3D SeaWiFS May 14, 1998
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SeaWiFS, TOMS, Bext May 14, 1998
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SeaWiFS, TOMS, Bext May 15, 1998
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SeaWiFS, TOMS, Bext May 16, 1998
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Surface Ozone Concentration
Superposition of daily maximum ozone and aerosol
extinction maps derived from surface visibility.
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The Global Aerosol ChallengeNeed to Learn More
and Faster

• The next generations will also be challenged by
  the global aerosols
• The aerosol dimensions include particle size and
  shape in addition to x, y, z, t and composition.
• Global aerosols are forced by poorly
  predictable biogeochemical processes like wind
  erosion, biomass burning, volcanoes and human
  actions.
• Do they harm human health and how? Do they cool
  and/or heat the atmosphere?
• How could we learn more and faster about the
  global aerosol system?

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New OpportunitiesSatellites, Internet and
Collaborative Spirit

• Satellite remote sensors allow continuous
  monitoring of the entire world
• The Internet facilitates virtually unlimited
  communication and the sharing, (recycling) of
  data, information and knowledge.
• There is a growing collaborative spirit in the
  scientific community
• The winds of technological and social changes are
  there but we need to learn how to harness them
  to sail from A to B.

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