1. Chapter 18 The Atmosphere

2. Earth’s Atmosphere Made of a mixture of lots of gases 79% 21%

3. Pressure –Decrease as you go up Density –Decrease as you go up

4. Layers of the Atmosphere Troposphere –Layer closest to surface (0 to 10 miles) 50% of all gases found below 3.5 miles –Most dense layer of air –Where weather occurs –Gets cooler as you go up Temperature inversion can happen –Cooler air gets trapped under hot air –Traps the pollutants causing smog

5. Layers of the Atmosphere Stratosphere –Second layer of the atmosphere (10 to 30 miles) 99% of all gases below 19 miles –Ozone is located here Shields life from the dangerous UV rays –Absorbs the UV rays given off by the sun –Makes this layer warm –Temperature increases as you go up

6. Layers of the Atmosphere Mesosphere –Third layer of the atmosphere –Layer with the coldest temperatures Thermosphere –Last layer of the atmosphere –Very hot temperatures –Gases very spread apart Some escape into space

7. Earth’s Atmosphere Original atmosphere –Mostly hydrogen, water vapor, ammonia, methane, carbon monoxide, carbon dioxide, and nitrogen

8. Earth’s Atmosphere Gases keep the Earth warm –Carbon dioxide and water trap heat –Known as the greenhouse effect Must have it to keep Earth suitable for life

9. Earth’s Atmosphere Plant’s evolved by using water vapor and carbon dioxide –Used photosynthesis (oxygen-carbon dioxide cycle)

10. Plants use carbon dioxide Plants produce oxygen Animals breath oxygen Animals exhale carbon dioxide

11. Changes to the Atmosphere Photosynthesis –Plants use carbon dioxide to make oxygen –Puts more oxygen in the air Respiration –Animals use oxygen to make carbon dioxide –Puts more carbon dioxide in the air Need a balance of carbon dioxide and oxygen to keep the atmosphere the way it is

12. Changes in the Atmosphere Human changes –Appliances add chlorofluorocarbons (CFC) CFC destroy ozone –Cut down trees and other plants –Burning fossil fuels Drive cars, heat buildings, manufacturing

13. Water Cycle and Atmosphere

14. Water evaporates from the surface into the atmosphere –Warmer temperature = more evaporation = more water vapor in atmosphere –Humidity Amount of water vapor in the atmosphere

15. Water Cycle and Atmosphere Dew Point –Temperature where water vapor condenses –Depends on humidity Higher humidity leads to higher dew point

16. Water Cycle and Atmosphere Water vapor condenses in air –Forms tiny drops of liquid water and ice Known as Clouds Clouds get very full and very heavy –Water will begin to fall because of the weight and gravity Known as precipitation –Rain, snow, hail, sleet

17. Types of Clouds Cirrus Clouds Cumulus Clouds Stratus Clouds Fog - Very Low Clouds

18. Pressure and Atmosphere Air pressure is read with a barometer –Weight of all atmosphere pushing down –Cool air has higher pressure –Drops in pressure indicate stormy weather High pressure = fair weather Low pressure = clouds and precipitation

19. Pressure and Atmosphere Difference in air pressure creates wind –Air moves from high pressure to low pressure Larger difference = stronger winds –Areas of equal pressure are connected by isobars on a weather map Close bars = strong winds

20. Coriolis Effect Close isobars = high winds

21. Fronts and Weather Air Masses –Body of air with the same temperature and humidity Front –Boundary between different air masses –Three main types Cold Warm Stationary

22. Fronts and Weather Warm Front –Warm air mass moves toward and over cold air mass –Clouds usually form Start as high cirrus clouds Later form heavy stratus clouds that release precipitation for a few days Weather Map Symbol

23. Fronts and Weather Cold Front –Cold air mass moves under a warm air mass –Very steep edge so cumulus clouds form quickly and are very heavy –High winds, thunderstorms, tornadoes occur here Weather Map Symbol

24. Fronts and Weather Stationary Front –Two different air masses sit along side each other –Act similar to a warm front –Weather usually stays the same for a few days Weather Map Symbol

26. Fronts and Weather Thunderstorms –Precipitation storms with lightning and thunder Lightning = sparks that jump between clouds and ground because of a difference in electric charge Thunder = sound of lightning moving through the air

27. Fronts and Weather Tornadoes –High speed, rotating winds that extend out of thunderclouds –Most common in Midwest region of the US from April until June –Watches are set when conditions are right –Warnings are set when one has been spotted

28. Fronts and Weather Hurricanes –Similar to tornadoes, but they form over water Water powers the hurricane so the longer it is over water, the worse it can be –Usually occur in late summer to early fall –Also called cyclones and typhoons in other parts of the world

29. Weather and Climate Climate –The average weather patterns of a certain area over many, many years –Depends on location on Earth and surface features in the area

30. Weather and Climate Temperatures are hotter closer to the equator because of more direct sunlight

31. Weather and Climate Seasons occur because Earth tilts and it moves around the sun

32. Weather and Climate Surface features of Earth –Mountains cause air to rise, cooling it, forming clouds –Oceans currents cause air to cool down –Bodies of water cause air to be more humid –Flat lands don’t stop air from flowing so lots of winds