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The Atmosphere

The Atmosphere

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The Atmosphere

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  1. The Atmosphere

  2. Key POINTS The Atmosphere (1) THE ATMOSPHERE - A layer of air that surrounds the Earth which is essential to life because it: 1. Acts as a SCREEN that blocks dangerous UV rays 2. RETAINS HEAT creating a relatively stable climate 3. Contains O2 needed for CELLULAR RESPIRATION & CO2 needed for PHOTOSYNTHESIS • Gravitational force keeps atmospheric gases close to the Earth’s surface; • 99% of atmospheric gases are found within the first 30km of the atmosphere’s total 10,000km

  3. 1.1 COMPOSITION OF THE ATMOSPHERE • 21% O2 • 78% N2 • 1% other gases (H2O, Ar, CO2, Ne, He, CH4, O3, etc. • - Water vapour is important in meteorology since it is responsible for the formation of clouds, • Precipitation and fog; • -The degree to which it is present (RELATIVE HUMIDITY) can be as much as 4% of air volume • Air also contains suspended solid particles: dust, pollen, soot, smoke… • - There are 5 main layers from the Earth’s surface

  4. Key POINTS Layers Troposphere: 0-15 km away; clouds/storms occur here; Temp. decreases with altitude 2. Stratosphere: 15-50 km away; contains Ozone Layer which absorbs sun’s UV light; Temp. increases with altitude (opposite of troposphere) due to the ozone layer’s influence; less air particles with altitude; jets and planes fly at this level 3. Mesosphere: 50-80 km away; contains very few air particles; coldest layer; Temp.< -80°C 4. Thermosphere: 80-500 km away; absorbs most solar rays; Temp. as much as 1800°C; meteors burn rapidly when contact this layer causing shooting stars; polar auroras found at this level 5. Exosphere: 500 km+; practically devoid of air so Temp. can’t be measured; satellites found here

  5. Key POINTS Atmospheric circulation • 1.2 ATMOSPHERIC CIRCULATION • - Global air masses around the Earth move constantly, fig.7.5 (p.226):

  6. Steps of air circulation: Warm, humid (lighter) air at the Equator rises (low-pressure zone) 2. Air moves towards the poles 3. Air cools becoming heavier and then falls over cold, dry regions (high-pressure zone) 4. Cold air from the poles moves towards the Equator while step 3 is happening This ongoing process (mixing of air: CONVECTION) helps distribute the heat coming from the sun.

  7. - Because our planet rotates, air cannot move in an expected N/S manner; the change in air mass trajectory due to the Earth’s rotation is called CORIOLIS EFFECT which moves air masses perpendicularly to its original position; this effect occurs in the troposphere; it causes cold/warm fronts and clouds • Northern hemisphere winds are • deviated to the right • Southern hemisphere winds are • deviated to the left • The CORIOLIS EFFECT stills puzzles scientists.

  8. Circulation cells and Prevailing winds Air moves in loops called CIRCULATION CELLS; 3 cells per hemisphere: 1. Polar Cells: air starts at the poles then proceeds towards the 60th parallel. It hits the Ferrel cells, warms up and loops back over towards the poles. 2. Ferrel Cells: warms air moves towards the poles then rises at the 60th parallel, loops over and moves back towards the 30th parallel. 3. Hadley Cells: warm air over the Equator (0 parallel) rises and moves towards poles, cooling and dropping at the 30th parallel.. - fig.7.7 (p.227)

  9. PREVAILING WINDS • Air also moves in surface currents called PREVAILING WINDS, which are under the influence of the Coriolis Effect and have several components: • 1. Polar easterlies: wind moving eastwards between poles and 60th parallel • 2. Westerlies: wind moving westwards between 60th and 30th parallel • 3. Trade Winds: easterly moving between Equator and 30th parallel

  10. Prevailing winds are an important component of weather. Storms, rain and other phenomenon move from West to East in Quebec because we are under the influence of Westerlies. • Jet streams are very strong high altitude winds(especially in winter) ; they travel West to East around the globe between circulation cells. • Two jet streams per hemisphere: • (1) Subtropical: At the 30th parallel • 11,000-14,000 m • Up to 400 km/hour in Winter • (2) Polar: Near the 60th parallel • 9,000-10,000 m • Up to 300 km/hr in Winter • Aircraft pilots going East, ride with a jet stream if possible but avoid them when going in the opposite direction.

  11. AIR MASSES: Are huge areas that can be several thousand km in size; stretch of air that has stayed put long enough to have acquired a specific temp. and humidity. • They are under the influence of winds. • They move as an entity. • They affect our weather. • FRONT: The line where two air masses meet. • An area of uncertainty and rapidly changing weather. • Two air masses don’t blend when they meet. • Denser, colder front slides under. • Lighter, warmer front slides over.

  12. Two clouds formed by air mass development are: CUMULUS: formed when a cold air mass meets a warm air mass and the warm air rises sharply forming puffy clouds which often bring wind and rain; fig.7.11 (p.229) NIMBOSTRATUS: formed when warm air mass gently moves over cold air creating light layered clouds; it brings slow moving clouds and rain; fig. 7.12 (p.230)

  13. ANTICYCLONES and DEPRESSIONS (vertical movement of air) • Anticyclone • As air cools particles move and collide less. Pressure causes particles to fall to the ground and start compressing them creating a HIGH-PRESSURE (H)zone (anticyclone); spirals in the northern hemisphere in clockwise motion and in the southern hemisphere, it is in counter-clock wise motion (Coriolis Effect) • -It prevents cloud-forming movements; encourages clear skies & stable weather • fig.7.13 (p.231) Next slide • Depressions • As air warms up, it rises creating an empty space under it or a LOW-PRESSURE (L)zone (a depression). It spirals in the northern hemisphere in counter-clock motion and in the southern hemisphere, it moves in clockwise fashion(Coriolis Effect) • - It encourages cloud formation and precipitation • - A strong depression can occur over tropical warm waters forming huge spirals moving as fast as 360km/hr leading to CYCLONES, HURRICANES or TYPHONES.

  14. 1.3 GREENHOUSE EFFECT • It is a process by which Earth retains a certain amount of solar heat that is essential to life • Certain greenhouse gases (H2O(g), CO2, CH4, N2O, etc.) have always been part of the • atmosphere • It is like a greenhouse roof, these gases retain some of the sun’s heat and release some of it • Process: • (1) Solar rays reach the Earth, heating the ground • (2) Ground releases some of this heat, in the form of infrared radiation, into space • (3) Some of this infrared radiation is trapped and returns to Earth’s surface

  15. - INTENSIFICATION OF GREENHOUSE EFFECT: • The concentration of greenhouse gases has been stable for thousands of years. • For example: CO2: it is naturally released by forest fires, volcanic eruptions and cellular respiration; it is absorbed by plant growth and oceans; in the last century the balance has been offset by COMBUSTION of HYDROCARBONS (oil, natural gas, coal) which dramatically increase the release of CO2 in the atmosphere; the more CO2 is released, the more heat will be trapped thus contributing to climate change, i.e., abnormal modifications in climate • Another example: CH4: 21 times more potent than CO2 in creating a trapping effect; it is released by farm animals when they digest grass or any greenery, through manure, paddy (Pads) field rice farming, decomposing waste (dumps), natural gas distribution, etc • Another example: N2O: (nitrous oxide) from fertilizer use, combustion of biomass, industrial uses (ex. nylon production) • - Between 1850 and 2005, Earth’s average temperature increased by 0.76°C. An increase of 2°C would bring serious disruptions (droughts, floods, heat waves andrising ocean levels)

  16. 1.4 THE CONTAMINATION OF THE ATMOSPHERE • Apartfrom man made greenhousegases, there are other substances thatareareconsidered as atmospheric CONTAMINANTS: • SO2 (Whencombinedwith water, itcreatessulfuricacid) and NOx (nitrogenoxides) are contaminants found in ACID RAIN and SMOG. • 2. Hg, As, Pb fromhydrocarbon combustion, wasteincineration and glass making. Theseaccumulate in living organismscausingproblems. • 3. CFC fromrefrigerationsystems and aerosolcans • Dust and solidparticlesfromfactorychimneys and vehicleexhaustcan enter lungscreating • problems. • - Thesepollutants are dangerousbecausetheycaninteractwithother substances, theyoccur in high concentrations and canbecarried over thousands of km polluting once pristineregions.

  17. THE THINNING OF THE OZONE LAYER • O3 forms a natural protective layer (stratosphere: 20-30km away) that absorbs some of the harmful UV rays (which are linked to skin cancers). When CFC’s are released into the atmosphere, a Chlorine atom is produced, this Chlorine atom then combines with an O3 molecule and destroys it. • O3 layer is very thin over Antarctica and a hole exists there, thus harmful UV rays reach the surface (although humans don’t live there, the impact on Antarctic ecosystems is unknown) • fig.7.20 (p.2237) • - in 1987 the Montreal Protocol was signed whereby 190 countries agreed to cease CFC usage by 2010. The O3 layer is expected to be restored to its normal thickness between 2055 and 2065.

  18. SMOG • Whensmoke and fogmeettheycreate smog. Athigh altitude (20-30km), O3is protective (O3 layer) but at a lower altitude (troposphere), itbecomes a pollutant in smog and is a lung irritant • Stepstothe production go smog: • 1. NOx (from car exhaust or factories) + UVrayslow altitude O3 • 2. Low altitude O3 + NO2 or SO2 smog

  19. 1.5 ENERGY RESOURCES • WIND ENERGY: • It is converted to mechanical energy and then into electricity • A renewable resource. Wind turbines can be up to 120 m in height. Huge blades turn in the wind, activating an electric generator in the body (nacelle) of the turbine; electricity that is produced descends the turbine tower and is directed to a distribution centre then to our homes, businesses, etc • Advantage: considered eco-friendly; no greenhouse gases produced • Disadvantage: eye sore. Wind speed is unpredictable thus energy produced is not necessarily constant. Its energy cannot be stored so it must be used with another more reliable system , for instance with hydroelectricity • - fig. 7.23 (p.238)

  20. (2) The effect of the Sun and the Moon on the Earth • - Sun is important: solar energy i.e. light and heat. The sun and the moon are also important: their gravitational pull causes the tides. • 2.1 SOLAR RADIATION • The Sun (star) is 75% Hydrogen and 25% Helium. Its core is 15 million °C. This core creates NUCLEAR reactions that transform H into He and creates light. Solar energy is transported by electromagnetic waves. It takes 8 min to travel between the Sun and the Earth. • - Although solar radiation contains all of the electromagnetic spectrum’s waves , only visible light, some infrared, and a minute amount of UV rays reach the Earth’s surface.

  21. - It is hotter near the Equator because of the spherical shape of the Earth; the differences in temperature on the globe create winds and ocean currents

  22. SOLAR RADIATION • although 1 hour of solar radiation is enough to supply the world energy for 1 year. The difficulty lies in the transformation of this energy into a form we can use. • There are three methods: • Passive heating systems: no specialized devices needed. A building made of heat absorbing materials (ex. concrete) is positioned southwards in a way to maximize sun penetration.

  23. 2. Photovoltaic cells: panel-shaped silicon containing structures that absorb the sun’s rays. Electrons (Negatively charged particles) in the panel become activated creating an electric current. Can be used on houses, highway signs and satellites. 3. Solar collectors: sun exposed glass panels transfer their heat to water in copper pipes, heated water can be used. It is effective in heating air, house water and pools.

  24. - Solar energy is eco-friendly but its use is not widespread because materials and equipment are expensive. Sunny days are sometimes unpredictable. It is useful in space and in the Far North.