Physics Photo of the Week
April 23, 2010
Appalachian Fog
Fog
is common both in April and October in valleys - especially on clear,
cold nights of relatively high humidity. When the sky is clear,
the ground air cools because the heat radiates out into space.
The
resulting cold air sinks into the local valleys and precipitates the
formation of fog as the temperature descends below the dew point.
This satellite image from October 25, 2009 is remarkable in that we can
clearly see the outlines of the valleys where the fog
accumulated. The Satellite photo was taken at 9:45 Eastern Time,
before the night's accumulation of fog has had a chance to
evaporate. The Piedmont regions of the Southeast USA was cloudy
when this photo was taken, but the Appalachian region in the upper left
half of the photo had cleared overnight allowing the fog to accumulate
in the valleys.
The foggy areas clearly show the morphology of the different
regions of the Appalachians. In western Virginia and eastern
Tennessee, the fog delineates the long valleys that are separated by
long ridges that are so noticeable when visiting
these areas. In eastern Kentucky and West Virginia, the valleys
marked by the fog show many dentritic or tree-like branches typical of
eroded plateaus. See if you can identify the Tennessee
River valley in northern Alabama,
the Cumberland River valley in southern Kentucky and north-central
Tennessee, and the Fontana Lake area in western North Carolina.
You can also see the narrow Sequatchie Valley in
Tennessee - a narrow rift valley in the Cumberland Plateau just
northeast of the Tennessee-Georgia-Alabama junction.
The photo at right shows a typical valley fog formation of the WWC Farm
taken in late September, 2006.
The NASA satellite photo was obtained from Interactive Weather
Satellite Images the Earth Science Office.
Physics
Photo of the
Week is
published weekly during the academic year on Fridays by the Warren
Wilson College Physics
Department. These photos feature interesting phenomena in
the world around us. Students, faculty, and others are invited to
submit digital (or film) photographs for publication and
explanation. Atmospheric phenomena are especially welcome.
Please send any photos to dcollins@warren-wilson.edu.
All photos and discussions are copyright by Donald
Collins or by the person credited for the photo and/or
discussion. These photos and discussions may be used for private
individual use or educational use. Any commercial use without
written permission of the photoprovider is forbidden.
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