Air Masses and Weather Fronts

Lesson 5

What is an air mass?

United States’ Air Masses (Page 49)

What happens when air masses meet?The boundary between air masses is called a

.There are 4 types and they can be found on

page:63 in your Catastrophic Events Book (Only 3)222 in your ScienceSaurus (All 4 with symbols)

Animations can be found on the following link: http://www.phschool.com/atschool/phsciexp/active_art/weather_fronts/

What happens when air masses rise or sink?When a “warmer” air mass is rising you have

low atmospheric (barometric) pressure.

This is represented by a red L on a weather map.

When a “cooler” air mass is sinking you have a higher atmospheric (barometric) pressure.

This is represented by a blue H on a weather map.

What makes the wind blow?When a cooler sinking air mass rushes in to

take the place of a warmer rising air mass we get wind.

Wind almost always goes from a higher pressure H area to a lower pressure L area.