1. LAYERS OF THE ATMOSPHERE Science 10 – Weather Unit

2. What are the layers? Troposphere Stratosphere Mesosphere Thermosphere Exosphere Tropopause Stratopause Mesopause

3. Definitions Troposphere – The layer closest to the Earth’s surface in which all weather occurs. Stratosphere – Contains the ozone layer; the later where volcanic gases can affect the climate. Mesosphere – The layer in which most meteors burn up after entering Earth’s atmosphere and before reaching Earth’s surface. Thermosphere – Temperature now increases with height and can reach 1,500°C. The international space station orbits this layer.

4. Definitions Tropopause – The boundary between the stratosphere and troposphere. Stratopause – The boundary between the mesopshere and the stratosphere. Mesopause – The boundary between the mesopshere and the thermosphere; the coldest place on Earth.

5. Activity – To Pass In Please complete activity 1-1B on page 12 of your textbook. Complete both the “What To Do” and “What Did You Find Out Sections” Due at the end of class. Please place in the Science basket at the back of the room. Remember to use graph paper and properly label your graph.

6. Temperatures in the Layers The atmosphere can be divided into four layers based on temperature variations. Temperature variations in the four layers are due to the way solar energy is absorbed as it moves downward through the atmosphere. The Earth’s surface is the primary absorber of solar energy. Some of this energy is reradiated by the Earth as heat, which warms the overlying troposphere. The global average temperature in the troposphere rapidly decreases with altitude until the tropopause.

7. Temperatures in the Layers The temperature begins to increase with altitude in the stratosphere. This warming is caused by a form of oxygen called ozone (O3) absorbing ultraviolet radiation from the sun. Ozone protects us from most of the sun’s ultraviolet radiation, which can cause cancer, genetic mutations, and sunburn. Scientists are concerned that human activity is contributing to a decrease in stratospheric ozone. Nitric oxide, which is the exhaust of high-flying jets, and chlorofluorocarbons (CFCs), which are used as refrigerants, may contribute to ozone depletion.

8. Temperatures in the Layers At the stratopause, the temperature stops increasing with altitude. The overlying mesosphere does not absorb solar radiation, so the temperature decreases with altitude. At the mesopause, the temperature begins to increase with altitude, and this trend continues in the thermosphere. Here solar radiation first hits the Earth’s atmosphere and heats it.

9. Quick Review 1. What is the basis for dividing the atmosphere into four layers? 2. Does the temperature increase or decrease with altitude in the troposphere? Stratosphere? Mesosphere? Thermosphere? 3. What is the approximate height and temperature of the tropopause? Stratopause? Mesopause? 4. What causes the temperature to increase with height through the stratosphere, and decrease with height through the mesosphere? 5. What causes the temperature to decrease with height in the troposphere?

10. Meteor Showers In The Mesosphere A meteorite is any object that has entered the atmosphere of another object and survived to impact the surface. Another way to explain a meteorite is to say that they started out as little chunks of rock and debris in space called meteoroids. They become meteors when they fall through a planet’s atmosphere; leaving a bright trail as they are heated to incandescence by the friction of the atmosphere (shooting stars). Pieces that survive the journey and hit the ground are called meteorites. Occasionally, an object large enough to be considered an asteroid will enter an atmosphere. Its remnants are also called meteorites if they impact the surface.

11. Meteor Showers In The Mesosphere The sizes of meteors that hit the planet are very small. Every hour, one million meteors hit the Earth’s atmosphere. Less than 160 get into the atmosphere. The biggest ones to actually hit the surface are 50 cm. Once a year, a 4 meter meteorite might hit. A 20 meter asteroid hits the Earth every 100 years. Every 2 million years or so, a 2 km asteroid will hit the Earth. One of the most well known meteors is the Peekskill Meteorite which hit on Oct 9,1992. The meteor covered a path of 800 km. A fragment had a mass of 27 lbs. http://www.youtube.com/watch?v=B17TmSSb5aI http://www.youtube.com/watch?v=B17TmSSb5aI What Exploded Over Russia? http://www.youtube.com/watch?v=-qZ6oiaSm00 http://www.youtube.com/watch?v=-qZ6oiaSm00

12. Layers Of The Atmosphere Assignment Friday, March 27 th – In Class. Please bring creative materials with you. This can include colourful paper, paint, pastels, water colours, markers, etc. Using pages 12-13 of your textbook and your notes, create a visual presentation of the four main layers of the atmosphere which includes the following: Altitude range of each layer. Temperature range of each layer. Interesting fact about each layer. Grading: Three things above shown: 12 points Visual appeal and clarity: 8 points Maximum score: 20 points