Chapter 17: The Atmosphere

1. Chapter 17: The Atmosphere • Weather - the state of the atmosphere at any given time and place. • Weather is constantly changing. • Climate - is weather over a long period of time, describes regions.

2. Measure Of Weather • 1. Temperature • 2. Humidity • 3. Precipitation Type • 4. Precipitation Amount • 5. Air Pressure • 6. Wind Speed • 7. Wind Direction

3. Atmosphere Composition • Different today than long time ago!How? • 2 main gases make up 99% • Nitrogen - 78% & Oxygen - 21% • Carbon Dioxide - small amount/important • Water (vapor)- amount varies • Both absorb heat given off by Earth

5. Dust particles are important - allow water droplets to form around them so we can have precipitation. • Ozone : O3 - found in stratosphere - protects us from UV radiation - we harm ozone by using CFC’s… aerosols, AC, fridges, etc. - Ozone hole in ‘85

6. Height & Structure • The atmosphere rapidly thins as you go away from Earth. • Pressure reduces as you go up. • At sea level air pressure is about 14.7 lbs per square inch. • Generally speaking temperatures cool as you go up!

7. 4 atmospheric layers: • Thermosphere - top layer,auroras, boundary to space, very thin amount of gases, temps. Increase as you go up • Mesosphere - next layer down, meteors hopefully “burn up” here, coldest layer, temperatures get colder as you go up.

8. Stratosphere - contains ozone layer, temperatures increase as you go up. • Troposphere - closest layer to Earth, contains all weather, temperatures decrease as you go up.

10. Earth-Sun relationships • Solar energy is not evenly distributed. • (latitude, time of day, & season) • Earth has 2 principle motions: 1.Rotation - spinning, causes night & day, 24 hours (23 hrs & 56 mins.) 2.Revolution - orbiting, gives us year 365.25 days

11. Earth’s Orientation • Seasonal changes occur because Earth’s position to the sun changes. • Earth’s 23.5 degree tilt gives us seasons • No tilt would mean NO seasons! • Read page 481!

13. 4 SEASONS: Summer and Winter Solstice means “sun stop” - summer solstice = June 21st=longest day - sun over the Tropic of Cancer - winter solstice = Dec. 21st=shortest day - sun over the Tropic of Capricorn

14. Equinoxes Equinox mean “equal night & day” - spring equinox = March 21st=12 hr sun - autumnal equinox = Sept. 21st=12 hr sun - sun over the equator for both of these

15. 17.2 Heating the Atmosphere • Heat – energy transferred from one object to another • Temperature – a measure of how fast the molecules are moving… • Hotter moves faster, colder… • Heat is transferred 3 ways • Conduction • Convection • Radiation

16. 1. Conduction • Heat transfer through touching • Touching a hot stove • Sticking your hands in the snow

17. 2. Convection • Heat transfer from moving particles, like air and/or water. • Cold water in the lake • Hot water moving around in a pot on the stove

18. 3. Radiation • Heat transfer by waves • Heat from the sun • Heat from a stove burner or fireplace • Electromagnetic waves (EM) • These are the waves from the sun • There are types of light we cannot see such as ultraviolet (UV), microwaves, infrared/heat waves (IR), x-rays…

19. What Happens to Solar Radiation? • Some is absorbed by the object • Some passes through the object • Some bounces off the object Reflection happens when light bounces off an object

20. From the sun… • 50% is absorbed by earth • 20% is absorbed by clouds and atmosphere • 30% is reflected back to space

21. Greenhouse Effect 1. Light from the sun hits Earth 2. Earth warms up and releases heat 3. The CO2 and H2O trap the heat like a blanket 4. Too much CO2 makes Earth too hot

22. 17.3 Temperature Controls • Temperature control – any factor that causes temps to vary from place to place. • Latitude – distance from equator… • Land or water nearby – land heats up faster and to a higher temperature. Water that’s nearby makes it less extreme.

23. 3. Geographic position – where you are makes a difference 4. Altitude – it gets colder as you get higher into the atmosphere. 5. Cloud cover – clouds keep it cooler in the day, but warmer at night! * Clouds reflect outgoing heat and/or radiation back to the earth

24. Albedo – how reflective a surface is. A high albedo reflects a lot of light. • Bright materials (snow) have a high albedo, so reflect heat/energy/light • Dark colored objects have a low albedo (pavement, grass) so they absorb light/energy/heat.