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August 6, 2002
NASA AND CANADA STUDY SMOKE FROM FLAMING CANADIAN FORESTS
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.
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.
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.
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.
For more information and images, go to:
For images of aerosols from Canadian fires, see:
For more information on the AERONET and AEROCAN programs, go to:
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Contacts:
Robert J. Gutro
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-4044)
Rgutro@pop900.gsfc.nasa.gov
Gilles Pelloille
Université de Sherbrooke, Québec, Canada
(Phone: 819/821-7388)
Gilles.Pelloille@USherbrooke.ca
Heather MacKey
Environment Canada, Meteorological Services of Canada
(Phone: 416/739-4766)
Heather.MacKey@ec.gc.ca
Willy Bruce
Communications and Client Services
Canada Centre for Remote Sensing
Natural Resources Canada
(Phone: 613/996-2648)
Willy.Bruce@CCRS.NRCan.gc.ca
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Blazing Canadian Fires Sweep Smoke and Aerosols Into the U.S.
During the weekend of July 6th and 7th, record setting amounts of aerosols (tiny particles of pollution) swept into the Mid-Atlantic and Northeastern U.S. from Canadian forest fires. This movie from the National Oceanic and Atmospheric Administration's Geostationary satellite shows the darker smoke plume moving southward through Toronto and New York City toward Washington, D.C. (to the left of the circulating band of white clouds). The optical depth influence of the two separate clouds over time was picked up by sunphotometers at Toronto and New York. CREDIT: NASA-GSFC GOES-Project
Animation - 1.4 MB .mov
Smoke From Distant Fires
This image of giant smoke plume from Canadian forest fires was generated from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Terra Satellite on Sunday, July 7th. More than 40 forest fires north of Québec City, Canada, created smoke that extended southward over the Great Lakes and eastern United States. Many are thought to have been ignited by lightning strikes. Active fires are indicated by the red dots east of James Bay, Canada in the upper left part of the image.
Where the smoke plume enters the United States over the state lines of New York and Vermont, it measures almost 200 miles wide. As the smoke descended down the U.S. eastern seaboard, it affected air quality and visibility in major cities including New York, Philadelphia, Baltimore and Washington, D.C. The image shows the smoke drifting out over the Atlantic Ocean, and back over North Carolina (bottom right). CREDIT: Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC
Graph of the Variation of Aerosol Optical Depth Measured By Ground Sunphotometers on July 6, 2002
The GOES satellite animation from July 6 (top image) shows a large smoke plume drift south while dividing into two. The two segments then branch off towards Toronto (depicted by red line) and New York City (depicted by blue line).
On the scale at the bottom of the graph, the 6 refers to July 6th and the fraction refers to fraction of 24 hours GMT, which is four hours later than Eastern Time. (To read the graph, for example, at noon GMT on July 6th is labeled 6.5, which would translate to 4pm Eastern Time).
The leading edges arrive at about the same time over the two AEROCAN/AERONET sunphotometer sites located near Toronto (Egbert Ontario) and in New York City (City College of New York, CCNY). Over New York City the smoke plume also forks into 2 joined segments which pass over the city in sequence.
The graph shows aerosol optical depth (aerosol concentration) variation measured by the sunphotometers on July 6th over Toronto and New York City as well as NASA/Goddard Space Flight Center (GSFC), Greenbelt, Maryland (green). The Toronto and New York City optical depth curves rise rapidly at the same time the GOES plumes pass over these sites. These are very large increases in optical depth which normally one only sees for clouds. However, the texture of the plume and the fact that the AERONET sunphotometer spectra indicated the particles were abnormally small (less than 1/10 of minimum cloud particle sizes) indicates that the plumes could not be clouds. Note also, the double peak in the New York City optical depth, which corresponds to the forked segments in the GOES animation.
The GSFC optical depth variation only began late in the day on July 6th but restarted with a vengeance on July 7th, rising to a peak value of 7 in the early afternoon (GSFC/NASA is south of the bottom limit of the GOES imagery).
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