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.

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

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—amount varies also important Both absorb heat given off by Earth

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 --is poisonous/found at lower levels --we harm ozone by using CFC’s --aerosols, A.C.,fridges, etc.

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! (NOT always true!)

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.

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

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

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!

4 SEASONS: 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 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

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

Conduction Heat transfer through touching Touching a hot stove Sticky your hands in the snow

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

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

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

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

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

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.

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! Albedo – how reflective a surface is. A high albedo reflects a lot of light.