Part 3 Why Do We Have Weather?

The Green House Effect Heat is trapped by our atmosphere The Sun’s light shines on the Earth Some sunlight is reflected back into space from the clouds Atmosphere

The Greenhouse Effect Without this Greenhouse Effect, the Earth would lose all of its heat. The Earth would be a very cold place to live. Atmosphere

The Air The Southern Hemisphere is getting most of the Sun’s light. The Northern Hemisphere gets much less. The Sun heats the Earth unevenly. The Air

Because of this, the air around the Earth heats unevenly, creating large bodies of air at different temperatures. The Air

These massive bodies of air are known as air masses.

An AIR MASS is a large body of air that has similar temperature and moisture properties throughout.

http://www. geography. hunter. cuny. edu/~tbw/wc. notes/8. air http://www.geography.hunter.cuny.edu/~tbw/wc.notes/8.air.masses/air_mass_source_regions.htm There are two basic types of air masses, a warm, moist air mass and a cool, dry air mass.

A warm, moist air mass forms in the tropical regions of our planet, close to the equator, usually over the water.

Cool, dry air masses form closer to the North or South poles and form over land.

© 2003 - 2006 Michael Ritter (mritter@uwsp.edu) When these two types of air masses meet, they create weather. The boundary between two air masses is called a FRONT.

© 2003 - 2006 Michael Ritter (mritter@uwsp.edu) A COLD FRONT is defined as an area where a cold air mass is replacing a warmer air mass.

Cold fronts generally move from northwest to southeast Cold fronts generally move from northwest to southeast. The air behind a cold front is noticeably colder and drier than the air ahead of it.

A cold front is represented by a solid line with triangles along the front pointing in the direction of movement and is colored blue.

© 2003 - 2006 Michael Ritter (mritter@uwsp.edu) A WARM FRONT is defined as the transition zone where a warm air mass is replacing a cold air mass.

Warm fronts generally move from southwest to northeast and the air behind a warm front is warmer and more moist than the air ahead of it.

When a warm front passes through, the air becomes noticeably warmer and more humid than it was before.

A warm front is represented by a solid line with half circles pointing towards the colder air and in the direction of movement.

On colored weather maps, a warm front is drawn with a solid red line.

1) True or False – With out the Green house Effect the earth would be a very hot place? 2) True or False – A front is a large body of air that has similar temperature and moisture properties throughout. 3) True or False – Where two air masses meet is called a front 4) True or False – Cold fronts form in the warm tropical regions of the world like Florida. 5) True or False – When a warm air mass replaces a cold air mass this is called a warm front.