Smoke Soars to Stratospheric Heights
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.