A new look at smoke from the Chisholm forest fire, which ignited on May 23,
2001 about 160 kilometers north of Edmonton in Alberta, Canada, provides
confirming evidence that dense smoke can reach the upper troposphere and
lower stratosphere. Scientists have postulated a link between fires in
northern forests and the observed enhancements in stratospheric aerosols,
but it is difficult to measure smoke aerosol heights directly. Here, height
information for the Chisholm fire was retrieved using stereoscopic
processing of data from multiple Multi-angle Imaging SpectroRadiometer
(MISR) cameras. These images were acquired on May 29, when the severity of
the fire had begun to stabilize after a cold front and strong low-level
winds caused rapid spread of flame and an eruption of large-scale
convection on May 28. This dramatic event was studied in detail by M. Fromm
and R. Servranckx, "Transport of forest fire smoke above the tropopause by
supercell convection," Geophys. Res. Lett., vol. 30, no. 10 (2003).
The two left-hand images are natural color views from MISR's nadir and 60°
forward viewing cameras in which a pall of yellowish smoke is apparent both
above the surface and above clouds in the top portion of the images. This
area is near the junction of Canada's Keewatin region and Northwest
Territory, and about 1200 km northward of the originalfire location. Lake
Athabasca is at the lower left. The second panel from the right is MISR's
standard stereo height product (derived from the nadir and the two 26°
cameras), while the right-hand panel is a specially-generated product using
MISR's 46° and 60° forward-pointing cameras. Because the smoke appears
thicker at the oblique view angles, better areal coverage is obtained and
the retrievals are less sensitive to the underlying cloud deck. The
southern portion of the smoke cloud is at an altitude of about 3.5 km;
however, the smoke further to the north has risen above the tropopause
(which is at about 11 km altitude) and intruded into the lower
stratosphere. These measurements indicate that smoke reaches heights of
about 12-13 kilometers above sea level. The height fields pictured here are
uncorrected for wind effects; wind-corrected heights (which have higher
accuracy but sparser spatial coverage) for this smoke pall are about 0.5 km
higher.
The Multiangle Imaging SpectroRadiometer observes the daylit Earth
continuously and every 9 days views the entire globe between 82° north and
82° south latitude. These data products were generated from a portion of the
imagery acquired during Terra orbit 7695. The panels cover an area of 380
kilometers x 1137 kilometers, and utilize data from blocks 36 to 43 within
World Reference System-2 path 40.
MISR was built and is managed by NASA's Jet Propulsion Laboratory,
Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra
satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD.
JPL is a division of the California Institute of Technology.