Three Types of Precipitation
Relief
• There are three reasons why air is forced
upward also forming three types of
precipitation.
• Relief Precipitation- caused by winds
carrying air up over a mountain barrier.
Convectional Precipitation
• Convectional precipitation results from the heating of
the earth's surface. The warm ground heats the air
over it. As the air warms, the air molecules begin to
move further apart.
• With increased distance between molecules, the
molecules are less densely packed. Thus, the air
becomes “lighter” and rises rapidly into the
atmosphere.
• As the air rises, it cools. Water vapour in the air
condenses into clouds and precipitation. This type of
precipitation is common in the Prairies and Ontario
Frontal Precipitation
• When masses of air with different
density (moisture and temperature
characteristics) meet, warmer air
overrides colder air. The warmer air
is forced to rise and if conditions are
right becomes saturated, causing
precipitation. In turn, precipitation
can enhance the temperature and
moisture contrast along a frontal
boundary.
• Fronts cause sudden changes in general
temperature, and in the humidity and
pressure in the air. Warm fronts occur
where the warm air scours out a
previously lodged cold air mass. The
warm air 'overrides' the cooler air and
moves upward. Warm fronts are
followed by extended periods of light
rain and drizzle, because, after the
warm air rises above the cooler air
(which sinks to the ground), it gradually
cools due to the air's expansion while
being lifted, which forms clouds and
leads to precipitation.