These images and data products from the Multi-angle Imaging SpectroRadiometer
(MISR) document extensive smoke from fires burning throughout Nigeria and
north central Africa on January 31, 2003. At left are natural-color views
acquired by MISR's vertical-viewing (nadir) and most oblique forward viewing
cameras. The images extend from arid Niger in the north (including the
dark-colored Aïr Mountains), through forested Nigeria, and beyond the Niger
Delta to the Gulf of Guinea and the open ocean. Smoke present in the lower
portion of the images, and a series of thin, high clouds, are more apparent
at the oblique view angle. Although numerous small smoke plumes emanate from
fires buring within the image area, some of the smoke can also be attributed
to fires that were burning across the north central African Sahel and savanna
regions at this time and during the previous two weeks.
A map of aerosol optical depth, which is a measure of atmospheric particle
abundance, is shown at center-right. MISR utilizes the changes in the
atmosphere's ability to transmit light and the variation in scene brightness at
different view angles to retrieve aerosol optical depth and deduce some of the
properties of the particles. A thick pall of smoke is present over Nigeria and
the Gulf of Guinea, indicated by green, yellow and red pixels over these
regions. Clear skies are indicated by the blue and purple pixels over the
desert regions and ocean. Places where clouds or other factors precluded an
aerosol retrieval are shown in dark gray.
The position of clouds appears to move with view angle relative to the ground
due to geometric parallax. MISR utilizes the parallax effect to generate its
stereo height fields. The right-hand panel is a stereoscopically derived cloud
mask (SDCM), which classifies regions as clear or cloudy based upon their
heights above the surface and is one of several cloud masks produced by MISR.
The high and low confidence designations are related to how well the stereo
height retrieval algorithms were able to determine the absolute height of the
clouds. The pall of smoke, unlike the clouds and underlying surface, does not
contain an organized spatial texture, and the stereo retrievals classify the
smoke-filled regions as clear despite the large abundance of airborne particles.
The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously
and every 9 days views the entire globe between 82 degrees north and 82 degrees
south latitude. These data products were generated from a portion of the imagery
acquired during Terra orbit 16602. The panels cover an area of about 380
kilometers x 2520 kilometers, and utilize data from blocks 74 to 92 within
World Reference System-2 path 189.
Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
Text acknowledgment: Clare Averill (Acro Service Corporation/Jet Propulsion Laboratory).
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