by David Murphy
Actually, fog evaporates.
As the sun's radiation warms the earth's surface, the air just above the ground also warms. Fog, which exists in this warming surface air, evaporates and disappears as this warming occurs. To say that fog lifts is a bit of a misconception, although it's easy to understand why the process is at times described this way. Fog has the appearance of lifting because it evaporates from the ground up. But in actuality, it's just disappearing at lower levels first. Later on, as the heat continues to rise higher from the ground, the top of the fog deck gets eaten away, too.
A more accurate way of describing the departure of fog is to say that it burns-off, since this alludes to the role of the hot sun in destroying the fog. The bottom line? I'm not a big purist on this one. While I usually say that fog is evaporating, I have no problem with either the burning off or the lifting descriptions, because they both do a good job of communicating this important change in the weather. But technically, evaporating is the most accurate description.
