Air Masses and Air Mass Weather By Diana L. Duckworth Rustburg High School Campbell County Virginia

Air Masses Very large body of air with uniform heat and moisture Forms in region with uniform conditions of heat and moisture Source area Described by temperatures & humidity Use air temperature & dew point temperature

Five Types of Air Masses mT Maritime Tropical Forms over tropical oceans (low latitudes) High humidity & high temperatures mP Maritime Polar Forms over polar oceans (high latitudes) High humidity & low temperatures All Maritime air masses have high humidity

Five Types cont’d cT Continental Tropical cP Continental Polar Forms over tropical land masses (low latitudes) Dry (low humidity) and high temperatures cP Continental Polar Forms over polar land masses (high latitudes) Dry (low humidity) and low temperatures cA Continental Arctic Forms over the arctic land masses (near poles) Very dry & very cold All continental air masses are dry

cA cP mP mP cT mT mT

Air Mass Source Regions Polar air masses form at high latitudes North of Polar Front & Jet Stream All polar air masses are cold Tropical air masses form at low latitudes South of the subtropical Jet Stream All tropical air masses are hot

Air Mass Weather 75% of the time weather is controlled by air masses Air masses form in one place and move into another area of different condtions Kind of weather depends on two things: Difference in temperature between air mass & ground Amount of moisture in air

Tropical Air Masses Move North Warm air over colder surface Heat flows from air to land (air cools) Cold air is stable, does not rise Continental air masses dry, clear weather Maritime air masses humid, fog forms when air cools

Polar Air Masses Move South Colder air over warmer surface Heat flows from land to air, so air gets warm Warm air rises – unstable atmosphere Continental air masses – fair weather cumulus clouds Maritime air masses – rising air produces showers