15.2 ATMOSPHERIC LAYERSThe Water Cycle Continues

Learning Targets

1. List the major layers of the atmosphere and their temperatures

2. Discuss why all weather takes place in the troposphere

3. Discuss how the ozone layer protects the surface from harmful radiation

Air Temperature1. Changes with altitude2. Warm air rises. Why?

a) Move vigorously & takes up space (more energy)b) Air pressure and density decreases

3. Cool air sinks. Why?a) Sluggish and takes up little space (less

energy)b) Air pressure and density increasesc) Cooler air sinks because it is denser than the

air beneath it

Atmospheric Layers1. Composition of Elements

a) Same throughout2. As altitude increases:

a) Pressure and Density decreases3. Temperature Varies

a) Changes in temperature is NOT regular

b) Temperature gradient – change in temperature with distance

Atmospheric Layers1. Based on how the temperature in

that layer changes with altitudea) Troposphereb) Stratospherec) Mesosphered) Thermospheree) Exosphere

TROPOSPHERE

Troposphere 0-10 km1. Heat source – Earth’s surface

a) Absorbs heat and radiate back in atmosphereb) Most dense~ 75% all atmospheric gasesc) Higher gravityd) Temperature decreases with altitude

2. Cold air on top of warm aira) Unstable wind and weather

3. Thicker at equator; thinner at the polesa) Caused by rotation of earth

4. Tropopause – thin layer which temperature does not change with height

Inversion1. Inversion: cold air is trapped

beneath warm aira) Stable; may persist for many daysb) Contributes to smog and air pollution

over citiesc) Often occurs in low lying regions

STRATOSPHERE

Stratosphere 10-50 km1. Heat source - Sun2. Temperature increases with

altitude3. Warm air on top of cold

a) Stable; calm4. Airplanes fly here5. Ozone Layer

a) Ozone = O3

b) 3O2 + UV radiation 2O3

MESOSPHERE

Mesosphere 50-80 km1. Heat source - Stratosphere2. Temperature decreases with altitude

a) Very few molecules to absorb Sun’s radiation

3. Very low pressure and density4. Very cold5. 99% of all atmospheric mass is below6. Meteors burn

THERMOSPHERE

Thermosphere 80+ km 1. Heat source - Solar Energy

a) Temperature increases with altitudeb) Feels cold due to low pressure

2. Feels cold because:a) Large amount of space between

molecules = no transfer of energy3. Solar wind causes auroras4. International Space Station orbits in

the upper part of the Thermosphere

Thermosphere 80+ km 1. Ionosphere – Solar radiation ionizes

gas molecules freeing electrons to create electric current

2. Aurora – Charged particles energize oxygen and nitrogen gas molecules

a) Each gas emits a particular color of light

Northern Lights

Southern Lights

Northern Lights

EXOSPHERE

Exosphere1. Essentially outer space

a) Trace amounts of gasb) Some gases escape into spacec) No outer limit

2.Solar wind – high-speed particles traveling outward from Sun

3. Sounds cannot be heard