AIR MASSES

A huge body of air that has similar temperature, humidity, and air pressure throughout.

Classified according to: Temperature Humidity TYPES OF AIR MASSES Classified according to: Temperature Humidity

An air mass’s temperature depends on where it’s formed. N. Pole An air mass’s temperature depends on where it’s formed. Equator

Tropical Air Masses Warm air mass Form in the tropics Have low pressure

Polar Air Mass Cold air mass Form north of 50*N and south of 50*S Have high air pressure

Humidity Whether an air mass is humid or dry depends on whether it formed over water or land.

Maritime Air Mass Form over oceans Water evaporates over oceans so air is very humid

Continental Air Mass Form over land in the middle of continents DRY

Putting them Together cP mP mP mT mT cT mT

How do Air Masses Move? The prevailing westerlies (moving from west to east) push air masses in the U.S.

Air Masses and Weather Fronts

Why do we need to know anything about weather fronts? When we look at weather fronts we can see what type of weather we are having. We can prepare for severe weather when looking at the types of weather fronts.

A boundary between two distinct air masses is called a weather front .

Weather Front Symbols ????Which is Which????

Types of Fronts There are 4 types of fronts: Cold Fronts Warm Fronts Stationary Fronts Occluded Fronts

Symbol: Warm Fronts A warm front occurs when a less dense air mass rides up over a more dense air mass.

Moving warm air mass collides with a slowly moving cold air mass Clouds, Storms, and rain accompany warm fronts.

Cold Fronts Symbol: A cold front occurs when a more dense air mass pushes under a less dense air mass.

Rapidly moving cold air runs into a slowly moving warm air mass and pushes the lighter warm air upward.

Cold Fronts can cause heavy snow or ice if there is enough water vapor in the air.

Occluded Front Symbol: A warm air mass is caught between two cooler air masses

The two cooler air masses meet in the middle and may mix. The warm air mass is cut off (or occluded) from the ground.

Stationary Front Symbol: Warm air mass and cold air mass meet Neither has enough force to move the other so they just stay in the same place. Where they meet, water vapor in the warm air condenses into rain, snow, fog or clouds Can stall out for days

Stationary Fronts: Unlike a fast-moving front, Stationary fronts often bring several days of cloudy, wet weather that can last a week or more.