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.