1. The Composition of the Atmosphere

2. Composition of the Atmosphere

3. Layers of the Atmosphere

5. Barometer

7. Air Pressure The force of the atmosphere pushing down on the earth due to the pull of gravity.

8. Air Pressure Air pressure decreases with an increase in altitude. The average air pressure at sea level is 1013 mb (millibars). Air pressure changes from day to day and even from hour to hour resulting is changes in weather.

9. Air Pressure

11. Air pressure on a weather map

12. The Layers of the Atmosphere The atmosphere is divided into sections based on temperature changes. Each time a temperature inversion (a reversal in temperature) occurs through the atmosphere a new layer begins.

13. Troposphere The layer we live in. Almost all of our weather occurs in it. Densest layer of the atmosphere containing about 90% of the atmosphere’s mass.

14. Stratosphere Second layer of the atmosphere. Contains the ozone layer. Temperature increases in the stratosphere due to the ozone layer absorbing and releasing Ultra Violet (UV) rays from the sun. The air is very thin and contains little moisture.

15. Ozone Layer in the Stratosphere

16. Ozone layer Shields the earth from harmful UV rays. UV causes sunburn and skin cancer. Not all UV is blocked by the ozone, but enough to protect us. The ozone layer is being depleted and has a hole in it.

17. Ozone layer

18. Mesosphere Has the lowest temperature in the atmosphere but would not feel the coldest. Temperature drops with increasing altitude.

19. Thermosphere Uppermost layer of the atmosphere Continues into space as the air molecules gradually decrease. Has a high temperature but would feel extremely cold.

20. Temperature and Heat Temperature is a measure of the average energy of particles in motion. Heat is a transfer of energy between objects at different temperatures.