Transcript Air masses - HRSBSTAFF Home Page

Over Land and Sea
Air Masses
Air Masses
 Air takes on the properties over which it lies
 Land air masses tend to be dry
 Oceanic air masses tend to be moist
Temperature Air Masses
 Tropical air masses tend to be warm
 Polar air masses tend to be cold or cool
Classification of Air Masses
refer to page 480
Name
Symbol
Moisture
content
Temperature
Fronts
 A front is the zone between two air masses
Cold Fronts
 Video
Cold Fronts
 Cold air mass catches up to a warmer air
mass
 Cold air pushes warm air upwards
 Cumulus cloud forms from condensing wate
vapour
 Heat energy lost from water vapour
condensation keeps air warm
 Can lead to forming a cumulonimbus cloud
Cold Fronts
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Usually brings rain
Can bring intense thunderstorms
Hail
Tornadoes
Warm Fronts
 Video
Warm Fronts
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Warm air masses overtakes a cold air mass
Warm front created
Gentle slope between two air masses
Warm air climbs over cold mass
Status clouds form
Later altostratus and cirrus cloud form
Precipitation last a long time
Air left warmer
Stationary Fronts
 Video
Stationary Front
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Meeting of cold and warm air masses
Neither air mass is moving
Some warm air rises over the cold air
Front stays in place for several days
Water vapour in warm air mass condenses
forming stratus clouds and rain
 Dreary, gloomy sky
Occluded Front
 Video
Occluded Front
 Two cold air masses meet pushing a
warmer air mass upwards.
 Warmer air mass is cut off from the ground
which is called occluded
 Numerous types of clouds are present
 May lead to period of steay rain
Highs and Lows Pressure Systems
 High pressure area is where air is
descending
 Areas where air is cooling because of cold
ground
 As air contracts it pulls more air in from the
top
 Pushs air out at the bottom
 Coriolis Effect creates an anticyclone
High Pressure Areas
 Diagram: textbook page 499
High Pressure Areas
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Areas of stable weather
Clear sky
Descending air has little moisture
No cloud form
Located within a single air mass
Huge air masses
Weather last several days
Low Pressure Areas
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Rising air leaves less dense air below
Hot ground causes air to rise
More air is pulled beneath rising air to replace it
Coriolis effect causes rising air to move to
the right
Counterclockwise direction
Created between air masses
Small in size
Bring unstable weather