Tiny water drops hovering in the air are
called fog. Fog is like a cloud, but it is near the ground, not high in the
sky. Thick fog makes is difficult to see the surrounding landscape.
Fog forms
from water vapor, which is water in the form of a gas. Water vapor in
the air condenses, or turns back into
liquid, when the air cools. Fog appears when this liquid gathers around bits of
dust in the air. A gentle wind helps fog to form and to stay in the air. If the
water vapor condenses on the ground insteat, it is called dew.
Fog is very common in valleys and near
bodies of water. It usually forms at night, when the air cools down. As the air
warms in the morning, the fog evaporate, or dries up. In colder places fog may last all day. Wind and tall objects such as trees
and buildings, can break fog into patches.
Fog also forms when warm
air blows slowly over a cool ocean or a lake. This kind of fog is also develop
over snow or ice. Cold air passing over warm land or water may also form fog,
as can rain falling from warm air to cool air near the ground.---Britania
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