Air Masses

• Vast pool of air with (fundamentally) the same temperature and moisture characteristics over its horizontal extent.

Air Mass Source Regions

Characteristics

• Flat terrain

• Little wind

• High Pressure

Air Mass Classification (based on:)

Moisture

• m for maritime

• c for continental

Temperature

• A for Arctic (60^o - 90^o N)

• P for polar (40^o - 60^o N or S)

• T for tropical (15^o - 35^o N or S)

• E for equatorial (15^o N - 15^o S)

• AA for Antarctic (60^o - 90^o S)

Air Mass Types

Generalized Map of Global Air Masses

• Continental Arctic (cA)- very cold; very dry

• Continental Antarctic (cAA) - very cold; very dry

• Continental Polar (cP) - cold & dry

• Continental Tropical (cT) - warm & dry

• Maritime Tropical (mT) - warm & moist

• Maritime Equatorial (mE) - very warm; very moist

• Maritime Polar (mP) - cool & moist

Air Mass modification

Examples

• cP air warms when moving south (cPk); enhances instability

• mT air cools at surface when moving over a cold ocean current (mTw); enhances stability

Fronts

• boundary between contrasting masses of air.

Semi-stationary fronts

• Polar Front - boundary between tropical and polar - type air.

• Arctic Front - boundary between polar and arctic - type air.

"Weather" fronts