Sun’s Energy

The sun’s energy heats the earth by emitting short wave radiation.  The earth absorbs some and reflects some of this energy (diagram)and this radiation and emits it back into the atmosphere as long wave radiation.  This heat then warms the atmosphere.  The average temperature of the atmosphere is 15^o Celcius. 

Atmosphere

Diagram of the layers of the Atmosphere

The atmosphere is composed (made up) of gases:

• Nitrogen                                              78%

• Oxygen                                                21%

• CO₂, neon, Ozone, Water Vapour          1%

 80% of the atmosphere’s gases are concentrated in the first 11Km of the atmosphere. 

This is because gravity pulls the gases to earth.

Atmospheric Pressure

The atmosphere has a weight therefore it exerts pressure on the earth.

This pressure is called Atmospheric Pressure.

Atmospheric pressure is measured by a Barometer.

Atmospheric pressure is recorded in Millibars.

Milibars are plotted on map and joined together to make Isobars.

Isobars are lines on a weather map connecting places of equal atmospheric pressure.

Uneven Distribution of the Sun’s Energy

What?

The sun’s energy is unevenly distributed across the earth.  Equatorial regions receive more energy than polar regions. 

Why?

The earth is roughly spherical or round.  This means that the Equator is closer to the sun than the poles. 

• The sun’s rays have to travel further to reach the poles than they have to travel to reach the Equator.  This means they lose more energy while travelling to the pole than while travelling to the Equator.

• When the rays reach earth, they are more spread out over polar regions than over Equatorial regions.  Therefore they are not as concentrated at the poles compared to the Equator.

Effect?

Countries closer to the Equator are warmer then those further away.(Diagram)