Download Precipitation - Ms. A de Boer

Precipitation
Types of Precipitation
 Rain
 Snow
 Dew
 Frost
 Hail
Facts about air we need to know
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Warm air is lighter than cold air
Warm air holds more moisture than cold air
Water holds heat longer than land
Air cools as it rises
When air passes over water, it picks up
moisture
Reasons why air may rise
1. It is forced up by relief (mountains)
2. It absorbs heat from the earth’s surface
3. It is pushed up by a cooler denser
(heavier) air mass
Air Pressure
 Air has weight = air pressure
 Low Pressure
– Warm air rising
– Bad weather
 High Pressure
– Cold air falls towards the earth
– Good Weather
 When a pressure goes from High to Low =
STORM
Types of Precipitation Storms
1. Relief (Mountain)
2. Convectional (absorbed heat)
3. Cyclonic (Frontal)
Relief Precipitation
1. As moist warm air rises
up the mountain, it
expands and cools
2. As the air cools, the rate
of evaporation decreases
but the rate of
condensation increases.
3. As more water
condenses, the clouds
become larger
4. When the clouds are too
heavy, they release
precipitation to the
ground
Windward vs Leeward
Windward
Side (wet)
Leeward
Side (dry)
Convectional Precipitation
(summer thunderstorm)
Cyclonic Precipitation
 Definition
– A large low pressure system that forms when a
warm air mass and a cold air mass collide.
Occurs when the Polar-Front Jet stream (cold, dry
air) collides with the warm tropical air of the Gulf
of Mexico (warm & moist air)
Cyclonic Precipitation
(aka Battle of the sky)
1. Cold, dense (heavy) air mass hits less dense warm moist
air, forcing it up
2. As air mass rises, it cools and condenses to form clouds
and precipitation.
3. Moisture falls through cold air below to cool the earth’s
surface.