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Transcript
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, 1850 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 3603600°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