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1. CONVECTIONAL RAINFALL
Convectional rain is caused by convection where the surface layer of the
atmosphere is heated causing the moisture laden air to rise. As it rises it
cools to form clouds. The unequal heating of the earth’s surface causes
convection. The resulting condition is that more widespread areas of colder air
separate rising currents of warm air. The colder air slowly sinks to take the
place of rising warm air.
condition of rising currents of warm air separated by more wide-spread areas of
slowly sinking air is referred to as CONVECTION. This is typical of
thunder storms during a hot summer. Convectional rain can also be found year
round in regions near the equator.
This rain is caused by depressions or Lows. Cyclonic rain originates where warm
tropical air meets cold polar air. The warm air overrides the cold air.
contrasting air masses make contact, an abrupt zone or boundary is formed. This
boundary is called a FRONT and is accompanied by rather abrupt changes in
temperature, pressure and humidity.
a mass of warm air moves into a region of cold air, the warm air overrides the
cold air mass, forcing the cold air to retreat. This situation is called a WARM
FRONT, which are characterized by several days of rain.
cold air mass moving into a warm air mass produces a frontal surface, which is
more vertical than that of a warm front. This situation produces a COLD FRONT.
Cold air masses advance rapidly and force the warm air mass upward where it
becomes cooled. The movement of the air mass is rapid enough to produce
cumulonimbus clouds. Rainfall is heavy but brief in duration.