Earth’s Atmosphere Chapter 3, Section 2 Describe the composition of the Earth’s atmosphere Describe the layers of the Earth’s atmosphere Explain 3 mechanisms of heat transfer in Earth’s atmosphere Explain the greenhouse effect

General Description of Atmosphere Mixture of gases Nitrogen Oxygen Carbon dioxide & others Addition/removal results in change Living organisms (plants & animals) Volcanic eruptions Vehicles/industries Insulates Earth’s surface

Composition of Earth’s Atmosphere Gases 78% Nitrogen 21% Oxygen 1% other (Ar, CO2, CH4, H2O) Atmospheric Dust Solid particles Soil, salt, ash fro fire & volcanic eruptions Particulate matter (combustion, skin, hair, clothing bits, pollen bacteria & viruses Aerosols (tiny liquid droplets) Creates air pressure Due to gravitational pull Greatest near Earth’s surface

Earth’s Atmospheric Layers (Ionosphere)

Earth’s Atmospheric Layers Divided into 4 layers based on Temperature changes Pressure changes

Location of Atmospheric Layers above Earth’s Surface

Troposphere Nearest Earth’s surface (up to 18 km) Makes up 75% of Earth’s atmospheric mass Densest layer Temperature & pressure decrease with altitude Except tropopause – very top of layer Stable temperature – called “cold trap” Wider at equator than poles Location of weather occurrence Uneven heating due to convection current & winds Causes cloud formation (rising water vapor cooled) Related to Greenhouse effect

Stratosphere 2nd layer above Earth’s surface (32 km thick, 18-50 km above surface) Temperature increases with altitude Contains ozone layer Reduces UV radiation Thinning in Europe, Asia, North America & Antarctica

Mesosphere 50-80 km above surface Coldest layer Temperature decreases with increase in altitude -30°C (-130°F) Slows, prevents meteors entering atmosphere

Thermosphere 80 – 1000 km above surface Very hot temperatures (200-2000°C or 360-3600°F) Ionization of gases N2 & O2 absorb X-rays & gamma rays Radiate light (auroras) Reflect radio waves Area where shuttles orbit

Energy Transfer in the Atmosphere Radiation Electromagnetic waves – absorbed & converted to heat Visible light, X-rays, UV, Gamma (from sun) Conduction Transfer by contact between different matter Convection Caused by temperature differences & changes in densities of materials Occurs only in fluids Creates currents

Energy Transfer Diagram

Atmospheric Energy Reaches Earth as electromagnetic radiation ½ entering atmosphere reaches surface ½ absorbed or reflected by gases, clouds, dust Oceans & land radiate energy back into atmosphere Prevents overheating of Earth’s surface Dark colors absorb more energy than lighter ones More energy released by darker colors Explains higher temperatures in cities than surrounding country sides

Energy Movement in Atmosphere Result of convection currents Air heated by Earth’s surface & rises into atmosphere Cools as it rises & becomes more dense & sinks Continual process results in circular movement of air (currents) Occurs in troposphere, resulting in weather occurrences (rain, wind, tornadoes, etc.)

Greenhouse Effect Warming of Earth’s surface & lower atmosphere Due to carbon dioxide, water vapor & other gases (methane, nitrous oxide) absorbing & radiating infrared waves Called “greenhouse gases” Maintain temperatures that support life Excess amounts of carbon dioxide & methane result in increased heat retention Caused by natural & industrial events Cause abnormal increases in temperatures (heat) Result in shifts in climatic zones, melting of polar ice caps, increased ocean levels around the world

How is Earth’s atmosphere like glass in a car? Both allow solar energy to pass through Both can absorb and stop heat from escaping