Atmosphere

Chapter 17

17.1 Atmospheric Characteristics

Atmosphere: the gaseous layer that surrounds the EarthI. In the past, gases came from volcanic eruptions

A. Water vapor was a major component of “outgassing”

B. Other gases included carbon dioxide, hydrogen, sulfur dioxide, and diatomic nitrogen

II. Composition of AtmosphereA. Earth’s lower atmosphere is a mixture of many

different gases we call air. B. Air is made of 4 main gases

1. 78.08% Nitrogen (N)2. 20.95% Oxygen (O2)3. 0.934% Argon (Ar)4. 0.036% Carbon Dioxide (C02)

C. Air contains particulate matter1. Dust and earth2. Chemicals3. Pollen4. Soot

D. Air is the same worldwide, with local variation (ex: H20 vapor)

III. The Structure of the AtmosphereA. Temperature changes greatly at different

altitudes (heights)B. The atmosphere is divide into layers based on

temperature differences, like the layers of the ocean.

How many layers do you see here?

IV. Atmospheric LayersA. Troposphere

1. The lowest layer, the one we live in.2. 0 to 15km above Earth3. Contains 80% of the atmosphere’s mass4. Most water vapor and weather are located

here5. Stops at tropopause6. Jetstream is located just below tropopause

(where most planes fly)7. Temperature decreases with altitude

B. Stratosphere 1. The second layer2. 15 to 50 km high3. Dry (no water vapor) 4. Stable (no weather)5. Ozone layer is located near the top

a. form of oxygen gas (O3 instead of O2)b. protects us from Sun’s UV rays c. absorbs UV rays and releases them as

heat6. Temperature increases with altitude in the

stratosphere7. Stops at stratopause

C. Mesosphere1. the third layer2. 50 to 90 km3. Temperature decreases with altitude as you

move away from the ozone layer4. Stops at mesopause

D. Thermosphere1. 4th layer2. Located above the mesopause3. 90 km and higher above the Earth4. The least dense layer of the atmosphere.5. Composed of layers of N2, O2, He, and finally

H that thins out into space.6. Temperature increases with altitude

because of the intense solar radiation7. Also called the ionosphere because the air

is highly ionized.8. Aurora Borealis (The Northern Lights) occur

here.

Thermal structure of the atmosphere

V. Earth – Sun RelationshipsA. Rotation:

1. the spinning of Earth around its axis2. Earth completes 1 rotation every 24 hrs.3. results in day and night4. fastest at equator, slowest at poles

At the equator, 1 rotation equals 40,074 km per 24 hours (1690 km/hr).Near the poles, 1 rotation equals nearly 0 km per 24 hours (0 km/hr), because the poles are nearest to the axis!

B. Earth’s axis 1. Imaginary rod running through the Earth

from the north pole to the south pole. 2. Earth rotates around this rod

counterclockwise3. The axis is tilted 23.5°4. Points straight towards Polaris, the North

Star! (This is why Polaris appears at the same place in the sky every single night of the year!)

C. Earth’s Revolution1. Revolution: one complete orbit of Earth

around the sun 2. 365.24 days, or 1 year

Earth Orbit.mp4

Remember, the Earth is tilted 23.5° on its axis. So, depending on where the Earth is in its orbit, 1 hemisphere is always tilted toward the sun, as the other is tilted away.

D. The Seasons1. When northern hemisphere is tilted toward

the sun Summera. more direct sunlightb. warmer tempsc. longer daysd. Summer Solstice:

i. longest day of the yearii. June 21-22iii. sun is directly over the Tropic of

Cancer

2. When northern hemisphere is tilted away from the sun Winter a. least direct sunlightb. colder tempsc. shorter daysd. Winter Solstice:

i. shortest day of the yearii. December 21-22iii. sun is directly over the Tropic of

Capricorn

3. Equinox:a. day and night are equal all over the worldb. 2 days out of the yearc. ½ way between the solsticesd. neither hemisphere tilts toward the sune. Sun is directly over the Equatorf. Vernal Equinox: March 21-22; beginning of

spring in the northern hemisphereg. Autumnal Equinox: Sept. 22-23; beginning

of fall in the northern hemisphere

page 482, Figure 8 – Solstices and Equinoxes

17.2 Heat and the AtmosphereI. Heat Energy

A. Radiation: the transfer of heat energy in the form of light1. In the form of electromagnetic waves2. Visible light, UV rays, infrared, etc.3. This is how heat energy from the sun

reaches Earth

B. Conduction: 1. The transfer of heat energy through touching

Ex: Touching a hot pan; walking barefoot on hot sand

2. Occurs through the collisions of atoms or molecules

C. Convection: 1. The transfer of heat energy in a gas or liquid

because of density difference2. Hot things are less dense than cold things

Ex: The air above a fire is heated, rises, and then heats the air above it

What type of transfer?

• Coffee warming a cup?• Conduction• Steam rising from coffee?• Convection• Pan warmed on stove?• Conduction• Fire warming your face?• Radiation

II. Heat and temperatureA. Temperature measures how fast the molecules

of a substance are moving.B. Boiling water has more movement than cold

water and a higher temperatureC. Heat measures the total energy contained in

the particles in a substance.1. A large cup of coffee has more heat energy

than a small cup of coffee2. Heat moves from high to low temperature

III. Insolation and the AtmosphereA. Insolation: incoming solar radiationB. Earth’s atmosphere receives only about 1/two-

billionth of the sun’s raysC. Global Heat Budget: shows the overall flow of

energy into and out of the system. (Fig 12)1. 30% reflected back out to space2. 20% absorbed by gases (CO2 and H2O) in

the atmosphere3. 50% is absorbed by Earth’s surface or used

during photosynthesis (eventually radiated back into space as heat)

Solar Radiation (page 486, Fig 12)

D. Greenhouse Effect1. Greenhouse gases (CO2, H20, CH4) absorb

and re-radiate heat into atmosphere2. Helps to keep Earth at a livable temp.

E. Global Warming1. An increase in the average global temperature

due to rising levels of carbon dioxide in the atmosphere.

2. Main causes: burning of fossil fuels and deforestation

3. Effects: a. rising sea levels due to melting polar iceb. unstable weather conditionsc. frequent heat waves and droughtsd. relocation of crop lands

17.3 Local Temperature Variations Key Concept : Insolation heats the Earth’s surface unequally.I. Time of Day

A. Warmest time = Afternoon1. Earth absorbs most heat at noon2. Earth re-radiates heat after noon

B. Coldest time = just after sunrise1. Ground and atmosphere lose heat all night2. Additional heat is lost from evaporation of

water at sunrise

II. LatitudeA. Warmest parts of Earth = near the equator• The sun’s rays are most directly overhead all

year long.B. Coldest parts of Earth = near the poles• The sun’s rays are least directly overhead.

Relationship of sun angle and solar radiation received on Earth

III. Time of YearA. Warmest season = summer

1. Sun directly overhead all season2. Days are longer

B. Coldest season = winter1. Sun is further away and not directly

overhead2. Days are shorter

Relationship of sun angle to the path of solar radiation and seasons due to Earth’s tilt

IV. Cloud CoverA. More clouds = colder days and warmer nights

1. Reflects insolation to space during day2. Traps heat from Earth during night

B. Less clouds = warmer days and colder nights1. Allows insolation to reach Earth2. Allows Earth’s radiation to escape to space

C. Clouds reduce the daily temperature range (max high to max low)

V. Type of MaterialA. Water and land don’t heat the same

1. Water heats more slowly than land2. Water cools more slowly than land

B. Color and texture also affect absorption1. Dark colors warm faster than light colors2. Rough textures warm faster than smooth

VI. Temperature Inversion…A. occurs when surface air is cooler than the upper

air.B. Prevents convection, no circulation occurs.C. Traps pollutants near surface.

VII. World Distribution of Temperature A. Map shows the effects of latitude on incoming

solar radiation.B. Isotherms – lines that connect points of same

temperatureC. Shows East to West lateral bandingD. Trend is decreasing temperatures from

equator to polesE. All measurements are for sea level.