These views of Hurricane Isidore were acquired by the Multi-angle Imaging
SpectroRadiometer (MISR) on September 20, 2002. After bringing large-scale flooding
to western Cuba, Isidore was upgraded (on September 21) from a tropical
storm to a category 3 hurricane. Sweeping westward to Mexico's Yucatan
Peninsula, the hurricane caused major destruction and left hundreds of
thousands of people homeless. Although weakened after passing over the
Yucatan landmass, Isidore regained strength as it moved northward over the
Gulf of Mexico.
At left is a colorful visualization of cloud extent that superimposes MISR's
radiometric camera-by-camera cloud mask (RCCM) over natural-color radiance
imagery, both derived from data acquired with the instrument's vertical-viewing
(nadir) camera. Using brightness and statistical metrics, the RCCM is one of
several techniques MISR uses to determine whether an area is clear or
cloudy. In this rendition, the RCCM has been color-coded, and purple = cloudy
with high confidence, blue = cloudy with low confidence, green = clear with
low confidence, and red = clear with high confidence.
In addition to providing information on meteorological events, MISR's data
products are designed to help improve our understanding of the influences of
clouds on climate. Cloud heights and albedos are among the variables that
govern these influences. (Albedo is the amount of sunlight reflected back
to space divided by the amount of incident sunlight.) The center panel is
the cloud-top height field retrieved using automated stereoscopic processing
of data from multiple MISR cameras. Areas where heights could not be
retrieved are shown in dark gray. In some areas, such as the southern
portion of the image, the stereo retrieval was able to detect thin, high
clouds that were not picked up by the RCCM's nadir view. Retrieved local
albedo values for Isidore are shown at right. Generation of the albedo
product is dependent upon observed cloud radiances as a function of
viewing angle as well as the height field. Note that over the short
distances (2.2 kilometers) that the local albedo product is generated,
values can be greater than 1.0 due to contributions from cloud sides.
Areas where albedo could not be retrieved are shown in dark gray.
The Multi-angle Imaging SpectroRadiometer observes the daylit Earth
continuously from pole to pole, 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 14669. The panels cover an area of about
380 kilometers x 704 kilometers, and utilize data from blocks 70 to 79
within World Reference System-2 path 17.
Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
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