Figure 5-15.-Nocturnal cooling over a land area producing
patchy ground fog (calm winds). (A) 1530 Local maximum
surface temperature; (B) sunrise-minimum surface
temperature.
nights versus short days in fall and winter are favorable
for the formation of radiation fog.
CONDITIONS FAVORABLE
FOR ADVECTION-RADIATION
FOG
Cold and moist are apt descriptions of air masses
that form in the late summer and early fall in the western
quadrants of the Bermuda High. Cyclogenesis off the
east coast of the United States, as well as the southerly
flow associated with continental polar highs that have
moved out over the ocean, are also cold and moist. If
Figure 5-16.-Nocturnal cooling over a land area
stratus (10- to 15-knot wind). (A) 1530 local
producing
maximum
surface temperature; (B) sunrise-minimum surface
temperature.
this air mass moves inland (replacing warm, dry, land
air), it may be cooled to saturation due to radiational
cooling during the long autumn nights with consequent
formation of fog or stratus. The fog is limited to the
coastal areas, extending inland between 150 and 250
miles, depending on the wind speed. On the east coast,
it is limited to the region between the Appalachian
Mountains and the Atlantic Ocean.
5-22
