Weather

Atmospheric Movement

Global air circulation patterns within the atmosphere held to Earth by gravity and warmed as heat radiates from Earth

Coriolis EffectThe apparent defection of moving air, as seen by an observer on Earth; apparent defection is a result of Earth's rotation

Air PressureThe force exerted on Earth’s surface by the weight of the air above the surface

Air pressure is greatest at sea level and lessens with increased distance from Earth’s surface.

WindA natural movement of air sometimes with considerable force from an area of high density and pressure to an area of low density and pressure

Air Masses

An air mass is a body of air extending over a large area (1,000 miles or more) that develops and retains specific characteristics of pressure, temperature and humidity

An air mass forming over a hot desert would be dry and hot.

One forming over a cold marine surface would be cold and humid.

High-Pressure Air MassAn air mass with

greater atmospheric pressure than the surrounding air masses; air moves away from the high pressure, traveling in a clockwise direction

High-Pressure Air Mass

HIGHS are denser, cooler and dryer than the adjacent air. The air is descending toward Earth’s surface.

HIGHS bring pleasant weather conditions in the summer and very cold clear weather in the winter.

Low-Pressure Air Masses

An air mass with less atmospheric pressure than the surrounding air masses; air moves towards the low pressure, traveling in a counterclockwise direction

Lows bring stormy weather.

Warm Front

Forms at the surface of Earth when a warm, moist air mass overtakes a cool, dense and dryer air mass

Slow moving and are characterized by a series of clouds getting lower and thicker as the front approaches.

Warm Front

Cold Front

Forms at the surface of Earth when a cold, dry air mass overtakes a warmer, humid air mass

Cold fronts are characterized by dramatic storms, thunder, lightning and sometimes tornadoes.

Cold Front

HurricaneA large, tropical

weather system consisting of an extreme low pressure air mass with heavy rains and wind speeds of at least 119km/h

Needs warm water to develop and stay strong