Overview
This lecture explains how air masses, fronts, and pressure systems interact to influence weather patterns, helping you interpret weather maps and forecasts.
Air Masses
- An air mass is a large body of air with uniform temperature and humidity.
- Air masses can cover thousands of miles and are moved by global wind patterns.
- Air pressure is the force exerted by air on Earth's surface; it’s higher in cold air (dense) and lower in warm air (less dense).
- The main types of air masses are Arctic (very cold), Polar (cold), Tropical (warm), and Equatorial (very warm).
- Air masses are also classified as maritime (formed over water, humid) or continental (formed over land, dry).
- Knowing where an air mass formed helps predict the weather it brings.
Fronts
- A front is the boundary where two air masses meet, often signaling a change in weather.
- A warm front occurs when warm air moves over cold air, causing light rain and then warmer, humid weather.
- A cold front forms when cold air pushes under warm air, leading to short, intense storms and cooler, drier weather.
- A stationary front forms when neither air mass advances, often causing prolonged clouds and light rain.
- An occluded front happens when a warm air mass is trapped between two cold ones, often causing severe weather and followed by less humid air.
- Weather maps use color codes and symbols (triangles, semicircles) to show front types and movement direction.
Pressure Systems
- High-pressure systems (marked "H") mean sinking air, clear skies, and stable weather.
- Low-pressure systems (marked "L") mean rising air, clouds, and stormy, changing weather.
- Pressure systems and fronts influence each other and create interconnected weather patterns.
Key Terms & Definitions
- Air Mass — Large body of air with uniform temperature and humidity.
- Front — Boundary between two air masses.
- High-Pressure System — Area with higher air pressure, usually clear weather.
- Low-Pressure System — Area with lower air pressure, often stormy weather.
- Maritime — Air mass formed over water (humid).
- Continental — Air mass formed over land (dry).
Action Items / Next Steps
- Complete the practice questions and extension activities for this lesson.