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NASA AND CANADA STUDY SMOKE FROM FLAMING CANADIAN
FORESTS
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NASA researchers and Canadian scientists have
established a network of ground sensors in Canada that are
currently studying smoke and haze created by Canadian forest
fires. Recently, the network detected record levels of
pollution seen over the U.S. eastern seaboard from fires in
early July.
NASA's AERONET (AErosol RObotic NETwork) program
consists of a group of ground-based remote sensing instruments
in the U.S. that can determine the amount of aerosols, or tiny
particles of pollutants, that are in the air over a given
location. The goal of this ground network is to assess the
optical properties of aerosols, specifically how much sunlight
they scatter and absorb, and to provide a double-check of
aerosol data as gathered by satellites.
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The Canadian subnetwork, called "AEROCAN," which stands
for Aerosols in Canada, is particularly important because of
Canada's large forested area and corresponding number of the
number of forest fires.
Brent Holben, an atmospheric scientist at NASA's
Goddard Space Flight Center, Greenbelt, Md., leads the AERONET
program in the U.S. that the Canadian program mirrors.
"AERONET consists of a series of ground-based remote sensing
sun photometers that measure aerosols globally," Holben said.
NASA and various federal agencies, universities and institutes
around the world have established these ground-stations, and
it has been expanding at a rate of greater than 10 percent per
year.
Holben said, "The AERONET ground network continually
verify the accuracy of data NASA collects from instruments
aboard NASA's Terra satellite." Terra looks at aerosols from
space down to Earth, while this project looks at them from the
Earth up toward space. When AERONET or AEROCAN data are
combined with satellite data in atmospheric computer models,
they can provide a complete, continuous and time dependent
picture of pollution over a region which environmental
managers can use to create health forecasts.
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NASA and Natural Resources Canada's Canada Centre for
Remote Sensing and the Environment Canada helped Canadian
scientists set up and maintain the pan-Canadian "AEROCAN"
subnetwork as part of the AERONET program's world-wide
expansion.
One particular area of interest for the AEROCAN network
is western Canada. Forest fires in western Canada have an
important affect on sun photometer measurements. According to
Norm O'Neill, an AEROCAN scientist from the CARTEL (remote
sensing) Centre at the Université de Sherbrooke in Sherbrooke,
Québec, Canada, 80 percent of the summertime optical effects
(such as haze) seen at sites such as Thompson, Manitoba and
Waskesiu, Saskatchewan can typically be traced to smoky
pollutant particles from Western Canadian fires. These smoky
conditions often create visibility problems for motorists and
pilots.
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Image 4
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Such was the case during the first week in July, when
forest fires flared up north of Québec City in eastern Canada
and AERONET was in full operation. Those fires generated a
mass of aerosols that was swept as far south as Washington,
D.C. A brownish haze resulting from the smoke covered major
cities such as Toronto, New York, Philadephia and Baltimore
during the weekend of July 6th and 7th.
The sun photometer located at NASA's Goddard Space
Flight Center measured the highest aerosol loading ever
recorded in the eastern U.S., approaching values of 1.5 to 2.
An aerosol optical depth of 1 means that only 37 percent of
the direct sunlight is getting through the aerosols in the
atmosphere. "On Sunday July 7th, the aerosol optical depth
values, indicative of the concentration of pollutants in the
air approached a value of 6, which was never recorded before
in this area," Holben said. An aerosol optical depth of 6
means only 0.25 percent of the direct sunlight is getting
through the aerosols to the ground, making for diffused light
and hazy conditions.
"We even have some optical evidence that forest fires
from as far away as Siberia can have a significant effect on
the amount of particles over North America, but clearly
nowhere near the influence of Canadian sources," said O'Neill,
who is currently stationed at Goddard where he is
collaborating with the AERONET group on aerosol optical
research projects.
The expansion of the AERONET network in Canada and
ongoing collaborative research projects are funded by NASA,
Natural Resources Canada's Canada Centre for Remote Sensing,
the National Research Council of Canada, Environment Canada,
and the National Science and Engineering Research Council of
Canada.
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