|
UNPRECEDENTED
FIRE SEASON IN SOUTHERN AFRICA AIDS AIR QUALITY, CLIMATE CHANGE
RESEARCH
The fires that raged across southern Africa this August and
September produced a thick "river of smoke" that observers
compared with the aftermath of the Kuwaiti oil fires in 1991.
NASA-supported studies currently underway on the event will
contribute to improved air pollution policies in the region
and a better understanding of its impact on climate change.
"Every
year African biomass burning greatly exceeds the scale of
the fires seen this year in the western United States," says
Robert Swap of the University of Virginia, one of the organizers
of the Southern African Regional Science Initiative (SAFARI
2000) field campaign. "But the southern African fire season
we just observed may turn out to be an extreme one even by
African standards. It was amazing how quickly this region
went up in flames."
 The
intensive SAFARI 2000 six-week field campaign was planned
to coincide with the dry-season fires. The experiment included
observations from NASA's Terra and Landsat 7 spacecraft, research
aircraft including NASA's ER-2 high-altitude jet, and several
ground stations. Over 200 scientists from around the world
participated in the campaign, which ended Sept. 25.
This
year the southern African fire season peaked in late August
and early September. The region is subject to some of the
highest levels of biomass burning in the world. SAFARI 2000
planners tracked the changing location of fires with daily
satellite maps provided by researchers at NASA's Goddard Space
Flight Center (Greenbelt, Md.). The heaviest burning was in
western Zambia, southern Angola, northern Namibia, and northern
Botswana. Some of the blazes had fire fronts 20 miles long
that lasted for days.
The
thick haze layer from these fires produced between Aug. 23
and Sept. 7 was heavier than campaign participants had seen
in previous field studies in the Amazon Basin and during the
Kuwati oil fires.
"We
observed a river of smoke that moved from northwest to southeast
over the subcontinent, causing heavy haze and reduced visibility
over Botswana and South Africa for about ten days in early
September," says SAFARI 2000 organizer Harold Annegarn of
the University of the Witwatersrand, Johannesburg.
According to veteran pilot Ken Broda, who flew NASA's ER-2
above the haze layer, "this was probably the worst in-flight
visibility I've seen anywhere, even during the oil fires following
the Persian Gulf war. From the ER-2's altitude of 60,000 feet,
where normal visibility can stretch 60 miles, I couldn't clearly
see the city of Johannesburg until I was directly overhead."
With
instruments on the ground, in the air, and in space, scientists
were able to sample the chemistry and measure the thickness
of the smoke plumes, map the movements of the haze layer,
and investigate how the smoke and fine aerosol particles affect
clouds.
"For
the first time we were able to track this annual haze from
its source and determine what happens to the aerosols in the
haze," says Annegarn. "The measurements we have now of carbon
transport in the haze, both as gases and particles, will add
important pieces to balancing global carbon budgets."
Studies
by research aircraft flying inside the pall of haze revealed
several surprises. Aircraft encountered puzzling layers of
extremely clean air sandwiched between polluted layers.
"The
pollution in the region is often very stratified with height
in the atmosphere," says Peter Hobbs of the University of
Washington, principal investigator for the experiments onboard
the university's Convair-580 aircraft. "Regions of heavy pollution
were separated by a very thin - just a few hundred feet deep
- layer of almost pristine air."
The
haze aerosols sampled were also more heat-absorbing than expected,
which means the haze layer may have a significant warming
influence on the region's atmosphere. "The aerosol in the
region was surprisingly absorbing," says Hobbs. "Such aerosols
may well add to the greenhouse warming effect, particularly
in the mid-troposphere. Most aerosols are thought to offset
that warming by scattering incoming solar radiation back into
space."
The
thick haze also contained high levels of ozone, a component
of smog, that frequently reached levels similar to those found
during air pollution alerts in major U.S. cities. Making the
first balloon-borne measurements of ozone during the height
of a southern African burning season, NASA Goddard scientist
Anne Thompson found that the impact of the haze may be greater
on climate change than on human health.
"Ozone
levels in U.S. urban centers may be more unhealthy at the
ground, but the ozone profiles we took in Zambia show that
much of the ozone here is in the middle and upper troposphere
where ozone's 'badness' is its effect as a greenhouse gas,"
says Thompson.
New
air quality data collected during the campaign will also help
governments in the region develop future environmental policies.
Annegarn and other South African scientists are working to
distinguish the industrial sources of air pollution from natural
sources such as emissions from vegetation and soils.
"With the SAFARI 2000 data we now have the first comprehensive
measurements of aerosols from the major industrial sources
in southern Africa," said Annegarn. "Together with the detailed
chemical analyses of these sources gathered during the campaign,
we can now evaluate the relative importance of industrial
emissions in the region's air pollution, which will contribute
to the development of both national and regional air quality
management policies."
U.S.
participation in the SAFARI 2000 campaign was sponsored by
NASA's Earth Observing System (EOS) project, a suite of spacecraft
and interdisciplinary science investigations dedicated to
advancing our knowledge of global change. EOS is managed by
Goddard Space Flight Center for NASA's Earth Science Enterprise.
A key objective of this year's campaign was to acquire measurements
for validating new data products from NASA's Terra spacecraft.
Back
to Top
 During
the dry-season in southern Africa, large areas of grasslands
burn each year, but this year's burning season was extremely
large. SAFARI 2000 field campaign scientists studied the extent
of these fires and the impact of the rising smoke on air pollution,
climate change, and clouds.
click
for high
res JPG of the first image | click for high
res JPG of the second image Click on pic to enlarge image
 One
of the goals of the SAFARI 2000 field campaign was to distinguish
industrial emissions from other sources of air pollution,
such as the smoke from the extensive grassland fires in southern
Africa.
Click
for high
res JPG | Click on picture to enlarge image
 NASA's
ER-2 high altitude aircraft (foreground) observed the southern
African haze layer from 60,000 feet while the University of
Washington's Convair-580 aircraft (background) used scientific
instruments to directly sample the haze. The planes are shown
at the base of flight operations for the SAFARI 2000 dry-season
campaign in Pietersburg, South Africa.
Click
for high
res JPG | Click on picture to enlarge image
 Instruments
onboard the University of Washington's Convair-580 research
aircraft sampled the smoke plumes produced by the unprecedented
fire season this year in southern Africa.
Click here for hi-res
image| Click
on picture to enlarge image
 Continuous
observations of an African savannah ecosystem are being made
from a NASA-funded research tower in Kruger National Park
(South Africa). The ground-based data are combined with observations
from aircraft and satellite to give a complete picture of
the region's ecosystems and their role in climate change.
Click
for high
res JPG | Click on picture to enlarge image
 Satellite
View of Ozone
High levels of
ozone, a component of smog, were produced by the fires in
southern Africa. Ozone from the inland fires concentrates
and flows east to the Indian Ocean and west over the Atlantic.
The ozone levels were frequently similar to those found in
air pollution alerts in major U.S. cities. This data was also
acquired by Earth Probe TOMS in September 2000.This is a still
from the movie clip showing ozone levels over southern Africa
on Sept. 25, 2000.
Back
to Top
|
