Clear skies on April 11, 2004 (top panels) contrast strongly with the dust
storm that swept across Iraq and Saudi Arabia on May 13 (bottom panels).
These data products from the Multi-angle Imaging SpectroRadiometer (MISR)
depict both the abundance of airborne dust, and its height above the
surface.
The natural-color views at left were captured by MISR's 70° forward-pointing
camera. In the May 13 image, the dust appears as yellowish ripples that
obscure a large part of southern Iraq. The dust is easy to discern over the
dark waters of the teardrop-shaped Lake Tharthar, and completely obscures
the smaller Lake Razzaza. Automated processing of data from multiple MISR
cameras was utilized to generate the cloud and dust height fields (center)
and aerosol optical depth retrievals (right).
On May 13, in the areas where the dust exhibited sufficient spatial
contrast between several view angles to be retrieved by MISR's stereoscopic
feature matching algorithm, analysis of the wind-corrected stereo height
field indicates that the tops of the dust attained heights above the
surface of almost 2 kilometers. Terrain elevation data are displayed when
the stereo matcher determines that a location is not covered by a feature
above the surface. For example, the purple areas in the center right-hand
portions of the height fields, correspond with the low, flat, valley
between the Tigris and the Euphrates Rivers. The retrieved heights shown
here are uncorrected for wind effects. The aerosol optical depth retrievals
utilize the change in surface brightness and contrast at different view
angles to obtain a quantitative measurement of aerosol amount. Here, an
optically thick atmosphere is indicated by the green or yellow pixels, and
clearer skies are indicated by blue pixels. The standard MISR aerosol
retrieval algorithm did not obtain results in places where the dust was too
thick to see surface contrast, and these pixels are shown in dark gray.
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 orbits 22950 and 23416.
The panels cover an area of about 380 kilometers x 704 kilometers, and
utilize data from blocks 63 to 67 within World Reference System-2 path 169.
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.