AIR MASSES AND FRONTS Chapter 16 Section 2 1

Humidity the amount of water vapor in the air 2

Air Mass- A large body of air with the same temperature and moisture that forms over certain areas of our planet. Air mass temperature and moisture are consistent throughout. 3

Air masses take on the characteristics of the area where they form. Air mass temperature and moisture are consistent throughout. Warm air forms over tropical regions near the equator. T- Tropical Cold air forms over polar regions. P- Polar Wet air masses form over water m- maritime Dry air masses from over land. c- continental 4

Moisture content is noted by the first letter. m – maritime – wet c – continental – dry Temperature is noted by the second letter. P – polar – cool T – tropical - warm 5

Description of air masses: –Continental polar (cP)- cool and dry Continental arctic-type of continental polar mass that is much colder-forms in the arctic circle –Continental tropical (cT)- warm (hot) and dry –Maritime polar (mP)- humid (wet) and cold; unstable Maritime tropical (mT)- humid (wet) and warm; unstable 6

mP- maritime polar air mass cP – continental polar air mass mT – maritime tropical air mass cT – continental polar air mass 7

Maritime Tropical Warm humid air masses from oceans near the tropics. They form over the Gulf of Mexico and the Atlantic Ocean. In the summer time maritime tropical usually bring hot humid weather. In winter, a humid air mass can bring heavy rain or snow.

Maritime Polar  Cool humid air masses form over the icy cold North Pacific and North Atlantic oceans.  The air masses affect the west coast more than the east coast.  In the summer they often bring rain, fog, and cool temperatures to the west coast.

Continental Polar  Form over central and northern Canada and Alaska.  Bring cool and cold air.  In winter they bring clear, cool, and dry air to most of northern America.  In the summer, storms may occur when continental air masses move south and meet maritime tropical that move north.

Continental Tropical  Hot dry air masses form only in the summer over dry areas of southwestern and northern Mexico.  Cover a smaller area than other air masses.  Bring hot, dry weather to the south.

An air mass is a large body of air that has similar temperature and moisture properties

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A front is a boundary between air masses. Four types of fronts and map symbols 1.Cold front 2.Warm front 3.Occluded front 4.Stationary front 14

WARM FRONT Warm air mass meets a cold air mass and pushes the cold air mass out of the way. Brings drizzly precipitation. Followed by clear warm weather. 15

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

Warm Front Animation: – 4.gifhttp://ww2010.atmos.uiuc.edu/(Gl)/guides/crclm/act/gifs/fpr 4.gif – Clouds, Storms, and rain accompany warm fronts. Moving warm air mass collides with a slowly moving cold air mass

COLD FRONT Cold air mass meets a warm air mass and pushes the warm air mass out of its way. Bring thunderstorms, rain or snow. Most tornadoes develop from thunderstorms on the edge of a cold front. Cold front followed by cooler drier air. 18

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

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

STATIONARY FRONT Cold air meets warm air. Not enough force to move either front. Many days of cloudy, wet weather. 21

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 Symbol:

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

OCCLUDED FRONT Warm air caught between two cold air masses. Brings cool temperatures with large amounts of rain or snow 24

aculty/ritter/images/atmos phere/weather/cold_occlus ion.gifhttp:// aculty/ritter/images/atmos phere/weather/cold_occlus ion.gif Occcluded Fronts : The two cooler air masses meet in the middle and may mix. The warm air mass is cut off (or occluded) from the ground.

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

Cold Front, Warm Front and Occluded Front Animation dina/weather.htmlhttp:// dina/weather.html ce/terc/content/visualizations/es2002/es2002 page01.cfm?chapter_no=visualizationhttp:// ce/terc/content/visualizations/es2002/es2002 page01.cfm?chapter_no=visualization Click on the above links. 27