Overview
This lecture introduces air masses, explains their classification by source region and surface type, and describes their characteristics and impact on weather.
Air Masses: Definition and Characteristics
- An air mass is a large parcel of air in the troposphere with uniform temperature, density, and humidity horizontally.
- Air masses can cover thousands of miles and stay cohesive.
- Temperature (warm/cold) and humidity (wet/dry) are key defining traits.
Air Mass Classification
- Air masses are labeled by surface type and source region: surface type uses lowercase (m = maritime, c = continental) and source region uses uppercase (T = tropical, P = polar, A = arctic).
- Maritime (m) air masses form over water and are moist; continental (c) form over land and are dry.
- Tropical (T) air masses develop in low latitudes and are warm; polar (P) form at high latitudes and are cool/cold; arctic (A) are from very high latitudes and are extremely cold.
Common Air Mass Types and Their Properties
- mP (Maritime Polar): cool and wet, forms over high-latitude oceans.
- cP (Continental Polar): cool and dry (very cold and dry in winter), forms over high-latitude continents.
- cT (Continental Tropical): hot and dry, forms over low-latitude land.
- mT (Maritime Tropical): hot and humid, forms over low-latitude oceans, brings humid summer weather (e.g., Texas summers).
- A (Arctic/Polar Arctic): very cold and very dry, forms over frozen Arctic/Antarctica, can cause extreme cold events like the 2021 Texas freeze.
Air Mass Distribution and Impact
- The source region (land/water, latitude) determines an air mass’s temperature and humidity.
- Distribution of air masses causes regional climate and affects local weather conditions.
- Movement of air masses plays a key role in changing weather patterns.
Key Terms & Definitions
- Air Mass — a large body of air with uniform temperature, humidity, and density.
- Maritime (m) — forms over water; moist.
- Continental (c) — forms over land; dry.
- Tropical (T) — forms in tropics; warm.
- Polar (P) — forms in high latitudes; cold.
- Arctic (A) — forms in polar regions; extremely cold.
- cP, mP, cT, mT, A — shorthand for major air mass types (see above for meanings).
Action Items / Next Steps
- Watch the next video for mechanisms of cloud formation.
- Review how different air masses affect weather in your region.