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/importantWater (vapor)- amount varies 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

- we harm ozone by using CFC’s… aerosols, AC, fridges, etc.

- Ozone hole in ‘85

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!

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:

Summer and WinterSolstice 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

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

17.2 Heating the Atmosphere

Heat – energy transferred from one object to anotherTemperature – a measure of how fast the molecules are moving…Hotter moves faster, colder…

Heat is transferred 3 waysConductionConvectionRadiation

1. Conduction

Heat transfer through touchingTouching a hot stoveSticking your hands in the snow

2. Convection

Heat transfer from moving particles, like air and/or water.Cold water in the lakeHot water moving around in a pot on the

stove

3. RadiationHeat transfer by wavesHeat from the sunHeat from a stove burner or fireplace

Electromagnetic waves (EM)These are the waves from the sunThere are types of light we cannot see

such as ultraviolet (UV), microwaves, infrared/heat waves (IR), x-rays…

What Happens to Solar Radiation?

1. Some is absorbed by the object

2. Some passes through the object

3. Some bounces off the object

Reflection happens when light bounces off an object

From the sun…50% is absorbed by earth20% is absorbed by clouds and

atmosphere30% 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.

1. Latitude – distance from equator…

2. 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!

* Clouds reflect outgoing heat and/or radiation back to the earth

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.