Air Masses

GEoDe CD

Mid-latitudes90

60

30

0

30

60

90

What is an Air Mass?

• Immense body of air

• 1000 miles across, several km thick.

• Characteristics:– Similar temperature– Similar moisture (humidity)– It moves– It originates in a source region– It brings constant weather conditions

Source Regionwhere the air mass starts

• Where air masses originate

• Have uniform physical characteristics

• Large areas

• The air stays put (stagnates) long enough to reach equilibrium.

• Does NOT have irregular topography (its FLAT: no mountains, land & water)

• It does NOT have cyclones

Continental (land) Polar COLD

Maritime (water) Tropical: WARM

Air masses

Temperature Polar or Arctic Tropical

Moisture / Humidity

Continental

Maritime

Cold, frigid air hot, warm air

Dry land

Wet ocean

cP or cA cT

mP mT

North American Air Masses

What air mass(s) influence OUR weather?

LOW pressure:

Warm, moist air

HIGH pressure:cold, dry air

Global Air Masses

Source Regions

cA _____________________________

cT: __________ ___________

LATITUDE

____________

_____________

_____________

_____________