Lake Eyre is a large salt lake situated between two deserts in one of
Australia's driest regions. However, this low-lying lake attracts run-off
from one of the largest inland drainage systems in the world. The drainage
basin is very responsive to rainfall variations, and changes dramatically
with Australia's inter-annual weather fluctuations. When Lake Eyre fills,
as it did in 1989, it is temporarily Australia's largest lake, and becomes
dense with birds, frogs and colorful plant life. The Lake responds to
extended dry periods (often associated with El Niņo events) by drying
completely.
These four images from the Multi-angle Imaging SpectroRadiometer contrast
the lake area at the start of the austral summers of 2000 and 2002. The
top two panels portray the region as it appeared on December 9, 2000.
Heavy rains in the first part of 2000 caused both the north and south
sections of the lake to fill partially and the northern part of the lake
still contained significant standing water by the time these data were
acquired. The bottom panels were captured on November 29, 2002. Rainfall
during 2002 was significantly below average ( http://www.bom.gov.au/ ),
although showers occurring in the week before the image was acquired
helped alleviate this condition slightly.
The left-hand panels portray the area as it appeared to MISR's
vertical-viewing (nadir) camera, and are false-color views comprised of
data from the near-infrared, green and blue channels. Here, wet and/or
moist surfaces appear blue-green, since water selectively absorbs longer
wavelengths such as near-infrared. The right-hand panels are multi-angle
composites created with red band data from MISR's 60-degree forward, nadir
and 60-degree backward-viewing cameras, displayed as red, green and blue,
respectively. In these multi-angle composites, color variations serve as
a proxy for changes in angular reflectance, and indicate textural
properties of the surface related to roughness and/or moisture content.
Data from the two dates were processed identically to preserve
relative variations in brightness between them. Wet surfaces or areas
with standing water appear green due to the effect of sunglint at the
nadir camera view angle. Dry, salt encrusted parts of the lake appear
bright white or gray. Purple areas have enhanced forward scattering,
possibly as a result of surface moistness. Some variations exhibited
by the multi-angle composites are not discernible in the nadir
multi-spectral images and vice versa, suggesting that the combination
of angular and spectral information is a more powerful diagnostic of
surface conditions than either technique by itself.
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 5194 and 15679.
The panels cover an area of 146 kilometers x 122 kilometers, and utilize
data from blocks 113 to 114 within World Reference System-2 path 100.
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.
Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
Text acknowledgment: Clare Averill (Acro Service Corporation/Jet
Propulsion Laboratory).
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