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FIRE
TOWERS IN THE SKY: NEW MAPS SHOW ANNUAL GLOBAL PORTRAIT OF FIRE
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Global
Fires
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These
Terra maps demonstrate fire behavior that would surprise
most people. High-profile fires that occur in the western
United States each year tend to draw a lot of attention,
but nearly the entire African continent south of the Sahara
Desertappears to burn each year. |
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Dramatic
new satellite maps showing fire activity across the entire
Earth for the past year are providing a unique picture of
seasonal and yearly fire activity. The maps are a milestone
in the use of satellite data for creating a long-term fire
record that is crucial for understanding the impact offire
on life and climate.
Using
daily, global fire detection provided by the Moderate Resolution
Imaging Spectroradiometer (MODIS) on NASA's Terra satellite,
scientists at Goddard Space Flight Center and the University
of Maryland have been mapping fire activity for the entire
surface of the Earth every day since February 2000. Never
before have scientists had the opportunity to map fire across
the entire Earth with such detail, accuracy, and frequency.
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Western Fires
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Images
from the MODIS sensor are used by firefighters to help
allocate precious firefighting resources. This movie
shows the distribution of fires in the western U.S,
during the active 2002 fire season through August 20.
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Christopher
Justice, of the Department of Geography at University of Maryland,
is the project's lead scientist. He says, "Fire plays
a central role in the Earth System. It impacts plant and animal
habitat, air and water quality, greenhouse gas emissions,
and human lives. MODIS' fire detection capabilities are a
big step forward in satellite-based fire mapping. MODIS can
detect fires across the entire Earth more accurately than
any previous satellite sensor, and it has a higher temperature
threshold, which means it can tell the temperature of even
very hot fires." The near-daily global coverage gives
scientists an excellent opportunity to study global fire behavior.
The
MODIS maps demonstrate the extreme fire seasons seen this
year in the US, Australia, and Siberia. The maps also demonstrate
fire behavior that would surprise most people, highlighting
the contrast between fire size and intensity and frequency.
Across the United States, large, intense fires in Western
forests attract a lot of attention, but it is the smaller,
more numerous fires in the Southeast that dominate the maps.
Across the world, the widespread fires that burn each year
in the savannas of Africa, Australia, and Brazil dwarf even
the most significant fire season in the western United States
as far as total acreage and number of fires.
But
that doesn't mean the fires in the United States are not globally
significant. Says geographer Rob Sohlberg of the University
of Maryland, "All fires are not equal in terms of the
vegetation, or fuels, consumed, even if they burn the same
total area. In general, African rassland and savanna fires
occur in areas with finer fuels containing less potential
energy in the form of stored carbon than mature trees contain.
In western U.S. forests, fuels have accumulated over long
periods of time and are much heavier. Individual wildfires
in these forested areas burn less total area, but consume
large amounts of fuel and release more stored energy, while
in Africa, individual grassland and savanna fires consume
less fuel, but are more numerous and cover a wider area."
The relative impact on climate of these different fire regimes
is still unknown.
According
to Sohlberg, global fire mapping is still in its infancy.
"Before we had the ability to detect fires from satellites,
we had no global record of the cycles of fire on Earth. Throughout
the world there are flood records going back a hundred years
or more, giving scientists a baseline to work from. Similar
long-term global fire records don't exist." Establishing
this baseline is essential for understanding the role of fire
in Earth's climate and how it might be changing.
Jacques
Descloitres manages the MODIS Rapid Response System at Goddard
Space Flight Center. Says Descloitres, "Global fire mapping
took a giant step forward when NASA launched the Terra satellite
in 1999. NASA and University of Maryland scientists quickly
established the MODIS Rapid Response Project, which provides
the MODIS fire detection data and true-color imagery via the
Web in near-real-time-usually within 2-4 hours of when the
sensor acquires the data."
This
global fire monitoring fits right into NASA's ongoing efforts
to use its resources to help manage natural hazards. Says
Timothy Gubbels, Program Manager of NASA's Solid Earth and
Natural Hazards Applications Program, "NASA wants to
facilitate the use of its remote-sending resources for all
phases of natural hazards management: risk assessment, response,
and impact assessment. The MODIS Rapid Response Project is
the perfect model for this."
Fire
detection data are fed to the USDA Forest Service as well
as the project's international partners, who use the information
to strategically allocate firefighting resources. When the
fires are over, data from MODIS and other Earth Observing
System instruments such as Landsat 7 and the Advanced Spaceborne
Thermal Emission and Reflectance Radiometer (ASTER) are used
to map the burned areas and plan rehabilitation.
Terra
is the flagship of the Earth Observing System series of satellites
and is a central part of NASA's Earth Science Enterprise.
MODIS' fire monitoring will continue with a second instrument
that launched onboard the Aqua spacecraft in May 2002.
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