December 22, 2021 - British Columbia
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Fog filled the valleys of British Columbia, Canada on the last day of
autumn, 2021. The Moderate Resolution Imaging Spectroradiometer (MODIS)
on board NASA’s Aqua satellite acquired a true-color image of the scene
on December 20.
Near the center and the southeast portion of the image, a bank of dense
fog obscures the land from view. In several other locations, light gray
fog flows through narrow valleys, flanked by bright-white snow that
tops the high elevations, creating a vein-like structure across the
region. In other locations, valleys appear green, thanks to the
vegetation on the valley floors.
Fog is simply a cloud lying on the ground. Like all clouds, it forms
when the air reaches its dew point, which is the temperature to which
an air mass must be cooled for the water vapor in it to condense into
liquid droplets.
Valley fog is common in the Pacific Northwest. On clear winter nights,
the ground and overlying air cool off rapidly, especially at high
elevations. Cold air is denser than warm air, and it sinks down into
the valleys. The moist air in the valleys gets chilled to its dew
point, and fog forms. If undisturbed by winds, such fog may persist for
days.
Image Facts
Satellite: Aqua
Date Acquired: 12/20/2021
Resolutions: 1km (1.6 MB), 500m (4.4 MB), 250m (3.5 MB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC
https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2021-12-22
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