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• Air Mass – LARGE parcel of air taking on characterictics of the area over which it forms.

• Source region - the area over which an air mass forms

• Air mass modification – when an air mass changes its characteristics

• Arctic – A or Antarctic – AA– EXTREMELY COLD: forms over poles

– VERY DRY: due to extreme colds

– Found above 60o

N and S latitude – North & south poles

Continental Polar - cP– VERY COLD: developed in sub polar regions

– VERY DRY:Due to the extreme cold & having developed over land

– Found in the interior of Canada & Alaska

Maritime Polar - mP– VERY COOL: due to high latitude but not

cold due to the influence of the ocean & warm ocean currents

– MODERATELY Moist: because of the cool temperature, but not as dry as cP because of evaporation from the water surface

– Found in cold waters of north Atlantic & Pacific. Primarily affecting west coast

• Continental Tropic – cT– VERY WARM: due to low sub-tropic

formation

– DRY: Formed over land

– Found in the deserts of the southwest & Mexico

• Maritime Tropic – mT– VERY WARM: due to lower sub-tropic

formation

– VERY HUMID: due to the very warm tropical oceans that it forms over

– Found in the subtropical oceans ie Caribbean Sea & Gulf of Mexico