Air Masses

Air Masses and Weather Systems

Definition of Air Masses

  • An air mass is a large region of air that is relatively homogeneous in temperature and moisture.

  • Air masses significantly impact local and regional weather.

  • The earth's differential heating leads to different air masses based on temperature and moisture access.

Types of Air Masses Affecting North America

  • Understanding the various air masses that influence weather in North America is critical, especially for students living in regions like Michigan.

  • Common types of air masses:

    • mT: Maritime Tropical

    • cT: Continental Tropical

    • mP: Maritime Polar

    • cP: Continental Polar

    • cA: Continental Arctic

Characteristics of Air Masses

  • Moisture Content:

    • C (Continental): Dry

    • M (Maritime): Moist

  • Latitude (Temperature):

    • A: Arctic or Antarctic

    • P: Polar (50-60 degrees N/S)

    • T: Tropical (20-35 degrees N/S)

Air Mass Codes and Their Meanings

  • The first letter of the air mass code indicates moisture content:

    • M = Maritime (moist)

    • C = Continental (dry)

  • The second letter indicates the temperature:

    • T = Tropical (warm)

    • P = Polar (cold)

    • A = Arctic or Antarctic (very cold)

    • E = Equatorial (very warm)

Combinations of Air Mass Codes

  • mE: Maritime Equatorial

  • cT: Continental Tropical

  • cP: Continental Polar

  • mP: Maritime Polar

  • cA: Continental Arctic

  • cAA: Continental Antarctic

Movement and Interaction of Air Masses

  • Air masses can originate from various regions and move towards the continental center. They may collide, leading to the creation of weather phenomena.

Specific Air Mass Characteristics

  • Continental Arctic (cA): Extremely cold, very dry, very stable; impacts the U.S. in winter with record low temperatures.

  • Continental Polar (cP): Cold, dry, and stable; can cause freezing conditions as far south as Texas and Florida.

  • Maritime Polar (mP): Typically involves warmer ocean temperatures, resulting in damp, cool conditions, potentially influencing nor'easters.

  • Maritime Tropical (mT): Warm and humid, contributes to convective uplift, particularly east of the Rockies, winter may lead to frontal lifting due to clashes with cold air.

  • Continental Tropical (cT): Typically produces very hot and dry conditions, especially in the summer.

Transition to Weather Fronts

  • The intersection of different air masses leads to the formation of fronts, which include:

    • Cold Fronts

    • Warm Fronts

    • Stationary Fronts

    • Occluded Fronts

  • These fronts significantly influence weather patterns.