Observations of the Natural Dissipation of Appalachian Valley Fog.
Environmental research papers,
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MASS
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The manner of the natural dissipation of Appalachian Valley fog is described for a narrow, steep-walled valley located near White Sulphur Springs, W. Va., was observed on 29 Aug 69, and for a wide, flat-bottomed valley located near Lewisburg, W. Va., that was observed 29 Sep 69. With the fog of the narrow valley, an apparent valley breeze developed at approximately 0915 EDT that transported the peripheral fog laterally upward into the intersecting canyons and ravines. The fog then began to exhibit a convective upper structure along the valley walls that gradually extended completely across the valley. Initial clearing occurred between the convective elements and progressed by means of the continued size diminution and disappearance of the elements. In the terminal dissipation phase of the fog, the sky cover conditions changed rapidly from broken to clear within a few minutes time from 1020 to 1033 EDT. Auxiliary data indicate that this is the usual, common mode of fog dissipation of two possible modes. The fog of the wide valley dissipated convectively in similar fashion except that obvious valley-breeze effects were lacking and that the terminal dissipation phase of the fog, proceeding from generally broken sky cover conditions to clear conditions, required a period of an hour or so. Much patterning of the clouds occurred during this phase which correlated with the topographical patterning of the places of lowest elevation within the valley.