Ice on the Great Lakes in False Color Infrared
On Feb. 19, 2014 the Moderate Resolution Imaging Spectroradiometer (MODIS)
aboard NASA’s Aqua satellite flew over the Great Lakes and captured this
striking false-colored image of the heavily frozen Great Lakes – one of the
hardest freeze-ups in four decades.
According to the National Oceanic and Atmospheric Administration (NOAA) Great
Lakes Environmental Research Laboratory (GLERL), ice cover on North America’s
Great Lakes peaked at 88.42% on Feb. 12-13 – a percentage not recorded since
1994. The ice extent has surpassed 80% just five times in four decades. The
average maximum ice extent since 1973 is just over 50%.
Unusually cold temperatures in the first two months of the year, especially
in January, are responsible for the high ice coverage. Very cold air blowing
over the surface of the water removes heat from the water at the surface. When
the surface temperature drops to freezing, a thin layer of surface ice begins to
form. Once ice formation begins, persistently cold temperatures, with or without
wind, is the major factor in thickening ice.
This false-color image uses a combination of shortwave infrared, near
infrared and red (MODIS bands 7,2,1) to help distinguish ice from snow, water
and clouds. Open, unfrozen water appears inky blue-black. Ice is pale blue, with
thicker ice appearing brighter and thin, melting ice appearing a darker
true-blue. Snow appears blue-green. Clouds are white to blue-green, with the
colder or icy clouds appearing blue-green to blue.
Image Credit: NASA/Jeff Schmaltz, MODIS Land Rapid Response Team, NASA
GSFC
NASA
Guillermo Gonzalo Sánchez Achutegui
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