Review Day Grab a book off windowsill Turn to page 66 Complete questions 1-6 on your own sheet of paper

THE ATMOSPHERE Composition & Layers

Objectives Describe the composition of Earth’s atmosphere. Describe the layers of Earth’s atmosphere. Explain 3 mechanisms of heat transfer in Earth’s atmosphere. Explain the greenhouse effect.

The Atmosphere Is the mixture of gases surrounding the Earth Composed of: Nitrogen Oxygen Carbon Dioxide How can gases be added/removed to atmosphere? Animals remove Oxygen, breath out Carbon Dioxide Plants take in CO2, add O2 to atmosphere Volcanic eruption adds gases Vehicles add & remove gases

Composition of Atmosphere Nitrogen 78% Oxygen 21% Argon Carbon Dioxide Methane Water vapor Addition to gases: atmospheric dust (soil, salt, ash, matter from combustion, skin, hair, bits of clothing, pollen, bacteria & viruses, and aerosols.

Air Pressure The atmosphere is pulled toward Earth’s surface by GRAVITY. Atmosphere is denser near surface. Most atmospheric gases located within 30 km of our surface (18.6 miles). The amount of air decreases at higher altitudes. So breathing at higher elevations is more difficult.

Why do planes fly so high, often 10km above the ground? Most commercial planes fly at about 10,000 m b/c the air at that altitude is less than half as dense as air 1,500 m about the ground Planes experience less drag & require less fuel when they move through thinner, less dense air. Less turbulent above cloud level.

Layers of the Atmosphere Divided into 5 layers based on temperature changes that occur at different distances Troposphere Stratosphere Mesosphere Thermosphere Exosphere

1. Troposphere Layer nearest Earth’s surface Extends to about 18km above surface Almost all weather occurs in this layer Densest atmospheric layer

2. Stratosphere Above troposphere Extends from 18km – 50km Temperatures rise as altitude increases b/c ozone in this layer absorbs the sun’s ultraviolet energy & warms the air. Ozone (O3) Almost all ozone is concentrated in stratosphere Ozone reduces the amount of harmful UV radiation that reaches Earth.

3. Mesosphere Layer above the stratosphere Extends to an altitude of about 80 km Coldest layer of the atmosphere Temp: as low as -93oC (-135oF)

4. Thermosphere (ionosphere) Farthest from Earth’s surface N & O absorb solar radiation = results in temps above 2,000oC (3,632oF) Air particles that strike each other transfer heat Air is so thin that particles rarely collide so little heat is transferred

5. Exosphere Uppermost region of Earth's atmosphere as it gradually fades into the vacuum of space. Air is extremely thin (almost airless) Extends from 400mi – 800mi

ATMOSPHERE Energy in the Atmosphere

Objectives Describe the composition of Earth’s atmosphere. Describe the layers of Earth’s atmosphere. Explain 3 mechanisms of heat transfer in Earth’s atmosphere. Explain the greenhouse effect.

Energy in the Atmosphere There are 3 mechanisms that transfer energy from the sun to the atmosphere Radiation: is the transfer of energy as electromagnetic waves Example: warmth you feel from fire Conduction: is the transfer of E in the form of heat from a warmer object to a colder object when they contact each other Convection: is the transfer of E that takes place when variations in temperature move the matter making up air. Example: vents in house

Convection Conduction Radiation

Greenhouse Effect The process in which greenhouse gases absorb & reradiate infrared radiation near the Earth Without it – Earth would be too cold for life to exist The gases in our Atmosphere trap the heat = greenhouse gases

Greenhouse gases Most abundant Water vapor Carbon dioxide Methane Nitrous oxide

Video: Greenhouse Effect https://www.youtu be.com/watch?v=5 zLuqSYF68E