browse image of orbit 16602 (340 KB JPEG)
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 A�r 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. The MISR Browse Image Viewer provides access to
low-resolution true-color versions of these images. 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.
Image courtesy NASA/GSFC/LaRC/JPL, MISR Team.
Text by Clare Averill (Acro Service Corporation/JPL).