This false-color image shows the current extent of snow cover over the
north-central and northeastern United States. This scene was acquired
on January 2, 2001, by the Moderate-resolution Imaging Spectroradiometer
(MODIS), flying aboard NASA's Terra spacecraft, and processed by the
University of Wisconsin-Madison's MODIS direct broadcast receiving
At visible wavelengths of light (e.g., 0.66 microns), snow cover is as
bright as clouds and is therefore difficult to distinguish from cloud
cover. However, at near-infrared wavelengths (e.g., 1.6 microns), snow
cover absorbs sunlight and therefore appears much darker than clouds.
This allows MODIS to discriminate between snow cover and clouds very
In this false-color image, land surfaces are green, water surfaces are
black, snow cover is red, and clouds are white. Those clouds that
contain a significant fraction of ice particles appear pinkish.
For the first time since 1918, snow fell in Buenos Aires, Argentina, late on July 9, 2007. The snow was still there the next morning when the Moderate Resolution Imaging Spectroradiometer (MODIS) flew over on NASA’s Terra satellite at 10:55 a.m. local time.