Transcript Precipitation

Precipitation
Rain, Snow, Sleet, hail
Steps that Lead to Precipitation
1. Air Rises (goes up)
2. Air Cools (colder as you go up)
3. Moisture Condenses (water droplets)
4. Precipitates (Falls to earth)
OROGRAPHIC (mountain)
Rainshadow
• Orographic precipitation results when warm moist air of
the ocean is forced to rise by large mountains. As the air
rises it cools, moisture in the air condenses and clouds
and precipitation result on the windward side of the
mountain while the leeward side receives very little
(rainshadow) . This is common in British Columbia.
CONVECTION (Heat)
• Convectional precipitation results from the heating of the
earth's surface that causes air to rise rapidly. As the air
rises, it cools and moisture condenses into clouds and
precipitation. This type of precipitation is common in
the prairie provinces and large cities in the summer.
FRONTAL (air masses meet)
When two air masses meet, one
must go over the other. When a cold
air mass meets a warm air mass the
warm air rises, cools and
condenses quickly. You get heavy
precipitation but of short duration
over a small area.
When a warm air mass meets a
cold air mass the warmer air mass
rises slowly over the cold air. As it
rises the warm air cools, moisture
in the air condenses, clouds and
precipitation result. You get a
steady rain of a longer duration
over a larger area.
Comparison Chart
Similarities
Orographic
(mountain)
Frontal
(air masses)
Convection
(Heat)
Moist Air Mass
YES
Yes / No
Yes/No
Air mass Rises
YES
YES
YES
Air mass Cools
YES
YES
YES
Precipitates
YES
YES
YES
Reason for
Rising
Mountain
Warm air meets
cold
Hot Ground
All Year
All Year
Summer
Heavy
Moderate
Low
Seasons
Amount of
Precipitation