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Earth's Atmosphere
- 2. Earth's Atmosphere What's an atmosphere? Air surrounding a planet Earth's atmosphere has 5 layers Different planets have different layers and different gases in their atmospheres What does it do? Protects from Sun's heat (and space's cold) day/night temps would be extreme without blanket of gases Protects from Sun's harmful rays solar (ultraviolet) radiation would destroy all life if not filtered out Thermosphere Mesosphere Exosphere Troposphere Stratosphere
- 3. Layers Identified by Temperature Temperature changes determine layers Top region and transition to next layer called: Tropopause Stratopause Mesopause Mesopause Tropopause Stratopause
- 4. Earth's atmosphere, a mixture of gases: • N2, O2, Ar, CO2, and others gases plus water vapor, dust, etc. •Earth's gravity holds more air molecules near it's surface than in the upper atmosphere where gravitational forces are weaker
- 6. Atmospheric Pressure Higher altitudes= Fewer molecules pushing on each other and their surroundings Lower pressure Less concentrated oxygen levels
- 7. Density Amount of matter within a specific volume # of atoms occupying a particular space how close together the atoms are packed SI base units = g/cm3 or g/ml
- 8. Altitude & Density As air pressure decreases, density of air also decreases Air particles are not squashed together as tightly the higher one goes (because of gravity) Air at sea level and 8km both have 21% oxygen But 21% of 100 = 21, while 21% of 10 is only 2! At 8km there are fewer molecules per cubic cm, so you take in less oxygen with each
- 10. Layers of Earth’s Atmosphere Troposphere Where we live Stratosphere Ozone layer Mesosphere Meteors burn up Thermosphere Space shuttle Aurora Borealis Exosphere Thin, outer layer Exosphere
- 11. Troposphere Thinnest layer (4 to 12 miles thick) Thickness depends on terrain, season, time of day & latitude Holds ~80% of Earth's atmospheric mass Highest pressure at lowest levels Most weather occurs here Water vapor (& clouds), wind, lightning Jet stream (river of 250 mph winds) is just below the Tropopause (upper boundary) or in the lowest parts of the stratosphere Temperature cools as you go up Sun heats ground, which radiates warmth to air above it Air is warmest near the ground 14o C (57o F) Air cools ~6.4o C every 1 km you go up Top of Troposphere is -50o C (-58o F)
- 12. Greenhouse Effect Solar radiation that reaches earth is absorbed by: Earth's surface (50%) land heats quicker and radiates sooner bodies of water heat slower and hold onto heat longer Earth's atmosphere (15%) 35% of Solar radiation is reflected from Earth's atmosphere Clouds Earth's surface (i.e. snow, sand) Some of the heat absorbed by Earth's surface is released into the atmosphere
- 13. Air Pollution Nitrogen Oxides Damage lung tissue Sources: car, plane, mower engines lightening burning N2 in air Sulfur Oxides Damage lung tissue Sources: burning coal volcanic eruptions Carbon Monoxide Causes asphyxiation Sources: gasoline engines (automobiles, chainsaws, trains, etc.) forest fires, woodstoves, cigarettes Airborne Lead Destroys brain tissue Source: leaded gasoline Particulates
- 14. Levels are Falling Except CO2
- 15. Stratosphere Thickness from 33 to 40 km (20-25 miles) Depends on Troposphere's thickness Top boundary (Stratopause) at 50km above sea level Contains the Ozone Layer Earth's "sunscreen" Temperatures rise as you go up Heat trapped by ozone warms layer -50o C to -3o C to (-58o to 27o Fahrenheit) Very stable/stagnant layer Little to no wind (not much mixing) Jet aircraft fly lower stratosphere No water vapor/clouds (very dry)
- 16. Ozone Layer O3 Molecules Absorbs UV light which cause skin cancer & cataract Absorbs heat Toxic to breathe
- 17. "Hole" in the Ozone Layer Chlorine & Bromine bind to oxygen & deplete ozone Mostly at the south pole where Artic winds carry Cl & Br up into the Stratosphere Localized & seasonal "thinning" - not a complete "hole" CFCs in refrigerants Montreal Protocol Some studies show reversal
- 18. Mesosphere About 35 km (22 miles) thick From 50 to 85 kilometers above sea level (31 - 53 mi.) Upper boundary called Mesopause Temperatures decrease with altitude Meteors burn up in this layer Seen as "shooting stars" Tiny particles (sand or pebble-size) Rock, dust or metal particles High speed (tens of thousands of miles/hr) Hard to study, not much known Sounding rockets take measurements
- 19. Thermosphere Thickest layer (250-560 miles) From 90 km (56 miles) to 1,000 km (621 mi) above sea level Upper boundary: Thermopause Predominant gases is Helium Temperatures rise with altitude Sun's activity (solar flares, day/night) affect the temperature Upper part ranges from 500°C - 2,000°C (3,632°F or higher)! "Ionosphere" - sublayer that contains plasmas (free p's & e's) ions aligned with Earth's magnetic fields collide with solar flare ions, causing auroras Different gasses cause different colors Radio waves bounce off ionosphere to extend range Space shuttle, satellites & ISS orbit in this layer Considered "outer space" by most people Gas molecules very far apart & very excited
- 20. Exosphere Region where atoms and molecules start to escape Earth's gravitation Very thin, outer layer No clear upper boundary with space Mostly Hydrogen
- 21. Homemade weather balloon experiment
- 22. Global Warming Average global temperatures have increased by about 1o C over the past 150 years. How do we know this?
- 23. Global Temperature Monitoring Land, air or sea? Urban “island” effect Weather balloon & satellite Satellite orbit adjustment US vs. UK boat measurements Historical estimates Little Ice Age “Frost Fairs” Medieval Warm Period Ice core & Tree ring sampling Statistics & adjustments
- 24. The Big Picture
- 26. Causes of Global Climate Change Solar activity Earth's elliptical orbit Volcanic Eruptions Greenhouse gases Carbon Dioxide Methane Nitrous Oxide Water Vapor
- 28. Carbon Dioxide Correlation doesn't = cause How much CO2 will cause significant change? Humans contribute 3% Increase of 65 parts per million over past 50 years 380 out of every million air molecules are CO2
Hinweis der Redaktion
- Average lung capacity is 5,000 cm3
- Average lung capacity is 5,000 cm3
- At one time, automobiles were a huge source of carbon monoxide pollution. Automobiles require so much energy that they burn gasoline at a very fast rate. The gasoline is burned so quickly that there is just not enough time to supply it with plenty of oxygen. As a result, incomplete combustion occurs and carbon monoxide is produced. In 1977, however, the U.S. government required car manufacturers to install catalytic (kat' uh lih tik) converters in all new cars. These devices convert more than 95% of the carbon monoxide produced by automobiles into carbon dioxide. After the government mandated this change in automobile manufacturing, the concentration of carbon monoxide in the air began to decline rapidly.
- The air we breathe today is much "cleaner" than the air our grandparents lived in. Industrial revolution caused huge increase in pollution, but legislation, scientific research and changes in manufacturing practices have all helped reverse much of the damage.
- The stratosphere is very dry; air there contains little water vapor. Because of this, few clouds are found in this layer; almost all clouds occur in the lower, more humid troposphere. Polar stratospheric clouds (PSCs) are the exception. PSCs appear in the lower stratosphere near the poles in winter. They are found at altitudes of 15 to 25 km (9.3 to 15.5 miles) and form only when temperatures at those heights dip below -78° C. They appear to help cause the formation of the infamous holes in the ozone layer by "encouraging" certain chemical reactions that destroy ozone. PSCs are also called nacreous clouds. Due to the lack of vertical convection in the stratosphere, materials that get into the stratosphere can stay there for long times. Such is the case for the ozone-destroying chemicals called CFCs (chlorofluorocarbons). Large volcanic eruptions and major meteorite impacts can fling aerosol particles up into the stratosphere where they may linger for months or years, sometimes altering Earth's global climate. Rocket launches inject exhaust gases into the stratosphere, producing uncertain consequences.
- Scientists know less about the mesosphere than about other layers of the atmosphere. The mesosphere is hard to study. Weather balloons and jet planes cannot fly high enough to reach the mesosphere. The orbits of satellites are above the mesosphere. We don't have many ways to get scientific instruments to the mesosphere to take measurements there. We do get some measurements using sounding rockets. Sounding rockets make short flights that don't go into orbit. Overall, there's a lot we don't know about the mesosphere because it is hard to measure and study. What do we know about the mesosphere? Most meteors from space burn up in this layer. A special type of clouds, called "noctilucent clouds", sometimes forms in the mesosphere near the North and South Poles. These clouds are strange because they form much, much higher up than any other type of cloud. There are also odd types of lightning in the mesosphere. These types of lightning, called "sprites" and "ELVES", appear dozens of miles above thunderclouds in the troposphere below. In the mesosphere and below, different kinds of gases are all mixed together in the air. Above the mesosphere, the air is so thin that atoms and molecules of gases hardly ever run into each other. The gases get separated some, depending on the kinds of elements (like nitrogen or oxygen) that are in them.
- Solar activity strongly influences temperature in the thermosphere. The thermosphere is typically about 200° C (360° F) hotter in the daytime than at night, and roughly 500° C (900° F) hotter when the Sun is very active than at other times. Temperatures in the upper thermosphere can range from about 500° C (932° F) to 2,000° C (3,632° F) or higher. The aurora is formed when protons and electrons from the Sun travel along the Earth's magnetic field lines. These particles from the Sun are very energetic. We are talking major-league energy, much more than the power of lightning: 20 million amps at 50,000 volts is channeled into the auroral oval. It's no wonder that the gases of the atmosphere light up like the gases of a streetlamp! The aurora is also known as the northern and southern lights. From the ground, they can usually be seen where the northern and southern auroral ovals are on the Earth. The northern polar auroral oval usually spans Fairbanks, Alaska, Oslo, Norway, and the Northwest Territories. Sometimes, when the Sun is active, the northern auroral oval expands and the aurora can be seen much farther south. The lights of the aurora come in different colors. Oxygen atoms give off green light and sometimes red. Nitrogen molecules glow red, blue, and purple.
- The temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. The most detailed information exists since 1850, when methodical thermometer-based records began. Satellites have been measuring the temperature of the troposphere since 1979. Balloon measurements begin to show an approximation of global coverage in the 1950s. Proxy measurements can be used to reconstruct the temperature record before the historical period. Quantities such as tree ring widths, coral growth, isotope variations in ice cores, ocean and lake sediments, cave deposits, fossils, ice cores, borehole temperatures, and glacier length records are correlated with climatic fluctuations. From these, proxy temperature reconstructions of the last 2000 years have been performed for the northern hemisphere, and over shorter time scales for the southern hemisphere and tropics. As well as natural, numerical proxies (tree-ring widths, for example) there exist records from the human historical period that can be used to infer climate variations, including: reports of frost fairs on the Thames; records of good and bad harvests; dates of spring blossom or lambing; extraordinary falls of rain and snow; and unusual floods or droughts. Such records can be used to infer historical temperatures, but generally in a more qualitative manner than natural proxies.
- Statistics, scale, adjustments for error