Foggy Morning in Greensboro, North Carolina

January 19, 2013

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Photographer: William Briscoe; William's Web site 
Summary Authors: William Briscoe; Jim Foster

The photo above shows a layer of fog shrouding trees and a small lake in Country Park, Greensboro, North Carolina. This is an example of ground fog or radiation fog, which typically forms on chilly mornings as the surface temperature drops due to loss of infrared energy (long wavelength) at night – radiative cooling. Temperatures fell to near freezing in the Greensboro area on this late fall morning. Note the dimmed disk of the Sun reflected in the lake. By the time the photo was snapped (at 9:54 a.m.), the fog was beginning to dissipate. Multiple scattering by the tiny fog droplets acts to increase the optical thickness of fog, and other clouds as well, so even fog layers less than about 100 ft (30 m) thick may effectively obscure the Sun from view. Compare this photo, taken on November 28, 2012, to a photo taken from the same location just five weeks earlier.

Photo details: Canon 7D camera; 24-70 mm lens; f2.8L; USM lens.