Unit 2: Weather (No Pictures)

Phase Change

a transition of matter from one state to another

Melting

The change in state from a solid to a liquid

Freezing

The change of state from a liquid to a solid

Boiling

The temperature at which a liquid changes to a gas

Vaporization

The change of state from a liquid to a gas

Sublimation

A change directly from the solid to the gaseous state without becoming liquid

Condensation

The change of state from a gas to a liquid

Dew Point

The temperature at which condensation begins

Air Pressure

The measure of the force with which air molecules push on a surface

Barometer

an instrument used to measure atmospheric pressure

Isobars

Lines joining places on the map that have the same air pressure

Convection Cell

Cycle in which heated material rises and cooler material sinks

Air Mass

A huge body of air that has similar temperature, humidity, and air pressure at any given height

Warm Front

the front of an advancing mass of warmer air

Cold Front

A front where cold air moves in under a warm air mass.

Stationary Front

A boundary between air masses that don't move possibly causing rain for several days

Occluded Front

a front where a warm air mass is caught between two colder air masses and brings cool temperatures and large amounts of rain and snow

Humidity

a measure of the amount of water vapor in the air

Anemometer

An instrument used to measure wind speed

Relative Humidity

The amount of water vapor in the air at any given time is usually less than that required to saturate the air. Expressed as a percentage.

Jet Stream

A narrow belt of strong winds that blow in the upper troposphere