The Earth’s Atmosphere - University of ginah/geog152/152_5_atmoscomp_web.pdfEarth’s Atmosphere Atmosphere…

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<ul><li><p>The Earths AtmosphereThe Earths Atmosphere</p></li><li><p>Earths AtmosphereEarths Atmosphere</p><p> Atmosphere is the gaseous layer that surrounds the earthAtmosphere is the gaseous layer that surrounds the earth</p><p> Is a mixture of gases that is naturally odorless, colourless, Is a mixture of gases that is naturally odorless, colourless, tasteless and formlesstasteless and formless</p><p> Air is blended so thoroughly that it behaves as if it were a Air is blended so thoroughly that it behaves as if it were a single gassingle gas</p></li><li><p>The AtmosphereThe Atmosphere</p><p>Air is held to the earth by the force of gravity:Air is held to the earth by the force of gravity:</p><p> The further away from the source of gravitational attraction The further away from the source of gravitational attraction (earth) the lower the attractional force(earth) the lower the attractional force</p><p> More air molecules are held closer to the earth than at More air molecules are held closer to the earth than at higher elevationshigher elevations</p><p> Atmosphere is more dense near the surface than at higher Atmosphere is more dense near the surface than at higher elevationselevations</p></li><li><p>The AtmosphereThe Atmosphere</p><p> No real top atmosphere drifts off to nothingness above No real top atmosphere drifts off to nothingness above about 100 kmabout 100 km</p><p> 97% of the weight and 100% of the water vapor reside in 97% of the weight and 100% of the water vapor reside in the bottom 30 kmthe bottom 30 km</p></li><li><p>DensityDensity</p><p>The The densitydensity (mass per unit volume) of the atmosphere quickly (mass per unit volume) of the atmosphere quickly decreases with increasing elevation above sea leveldecreases with increasing elevation above sea level</p><p> Density of the atmos can be measured as it exerts its Density of the atmos can be measured as it exerts its weight as a pressure (force per unit area)weight as a pressure (force per unit area)</p><p> The pressure the atmos exerts on the surface is know as The pressure the atmos exerts on the surface is know as air pressureair pressure Air pressure at Air pressure at sea level = 1013 mbsea level = 1013 mb Air pressure at the top of the stratosphere (50km) = 0.78 mbAir pressure at the top of the stratosphere (50km) = 0.78 mb</p></li><li><p>Composition of the atmosphereComposition of the atmosphere</p></li><li><p>Proportion of Elements in Dry Air (by volume) Nitrogen N2 78% Plants</p></li><li><p>Proportion of Elements in Dry Air (by volume) Nitrogen N2 78% Plants Oxygen O2 21% Animals</p><p>Together, Nitrogen and Oxygen account for99% of the atmosphere, by volume!</p></li><li><p>Proportion of Elements in Dry Air (by volume) Nitrogen N2 78% Plants Oxygen O2 21% Animals Argon Ar 0.93% Inert Gas</p><p>93% of the remaining 1% is Argon, an inert gas!</p></li><li><p>Proportion of Elements in Dry Air (by volume) Nitrogen N2 78% Plants Oxygen O2 21% Animals Argon Ar 0.93% Inert Gas Carbon Dioxide CO2 0.0325% Plants</p></li><li><p>Proportion of Elements in Dry Air (by volume) Nitrogen N2 78% Plants Oxygen O2 21% Animals Argon Ar 0.93% Inert Gas Carbon Dioxide CO2 0.0325% Plants Neon Ne 0.0005% Inert Gas</p></li><li><p>Proportion of Elements in Dry Air (by volume) Nitrogen N2 78% Plants Oxygen O2 21% Animals Argon Ar 0.93% Inert Gas Carbon Dioxide CO2 0.0325% Plants Neon Ne 0.0005% Inert Gas Krypton Kr 0.0001% Inert Gas</p></li><li><p>Proportion of Elements in Dry Air (by volume) Nitrogen N2 78% Plants Oxygen O2 21% Animals Argon Ar 0.93% Inert Gas Carbon Dioxide CO2 0.0325% Plants Neon Ne 0.0005% Inert Gas Krypton Kr 0.0001% Inert Gas Hydrogen H2 0.00005% Helium He </p></li><li><p> Water Vapor H2O 0 to 4% Ozone O3 0.0 to 0.0012% Chlorofluorcarbons CFCs (e.g., Freon) Changing Concentrations of:</p><p> Ozone Carbon Dioxide Methane Water Vapor</p><p>The Atmosphere</p><p>ClimateChange!</p></li><li><p>Important Roles Played by Trace GasesImportant Roles Played by Trace Gases</p><p>Carbon DioxideCarbon Dioxide An important absorber of outgoing terrestrial radiationAn important absorber of outgoing terrestrial radiation</p><p> It, along with water vapor, serve as the primary means It, along with water vapor, serve as the primary means of preventing rapid heat loss from the earth and of preventing rapid heat loss from the earth and atmosphere back into spaceatmosphere back into space</p></li><li><p>Important Roles Played by Trace GasesImportant Roles Played by Trace Gases</p><p>Water Vapor - An important absorber of outgoing terrestrial energy</p><p> Amounts vary from 0 to 4% depending on of evaporating water available and distance that source</p><p> This can cause tremendous differences in temperatures within the atmosphere</p><p>http://weather.unisys.com/satellite/sat_wv_us.html</p><p>http://weather.unisys.com/satellite/sat_wv_us.html</p></li><li><p>Important Roles Played by Trace GasesImportant Roles Played by Trace Gases</p><p>Liquid Water Causes clouds to form this affects the amount of heat </p><p>absorbed by the earth and atmosphere</p><p> Can vary tremendously within the atmosphere</p></li><li><p>Insolation losses in the atmosphereInsolation losses in the atmosphereDust - Gas molecules, dust, and other particulates areimportant because they can cause the suns rays to be scattered or absorbed</p><p>Scattering - visible light rays to be turned aside in allpossible directions. Under clear sky conditions, scattering sends about 5% of the incoming solar radiation back to space.</p><p>Absorption - Solar rays strike gas molecules and dust, andtheir energy is absorbed and temperatures rise. This accounts for about a 15% decrease in solar radiation.</p><p>Both carbon dioxide and water vapor are capable of directlyabsorbing some wavelengths of solar radiation.</p></li><li><p>Electromagnetic RadiationElectromagnetic Radiation</p><p>Electromagnetic radiation can be:Electromagnetic radiation can be:</p><p> Absorbed Absorbed increases the energy content of the object, increases the energy content of the object, like a black car in the summerlike a black car in the summer</p><p> Reflected Reflected bounce the energy back toward the source, bounce the energy back toward the source, like a mirrorlike a mirror</p><p> TransmittedTransmitted pass through without absorption or pass through without absorption or reflection, like a pane of glassreflection, like a pane of glass</p></li><li><p>Electromagnetic RadiationElectromagnetic Radiation AlbedoAlbedo percent of solar/shortwave radiation that is percent of solar/shortwave radiation that is </p><p>reflected from a surface.reflected from a surface.</p><p>New snow:New snow: 80%80% Old Snow: Old Snow: 50%50%Clouds:Clouds: 50%50% Ice: Ice: 35%35%Dark, wet soil:Dark, wet soil: 5% 5% Light, dry soil: Light, dry soil: 40%40%Asphalt:Asphalt: 5% 5% Forest: Forest: 15%15%Grass:Grass: 20%20% Crops: Crops: 20%20%</p><p>Water high incident angleWater high incident angle 50%50%Water low incident angleWater low incident angle 5% 5%</p><p> Average albedo of the earths surface:Average albedo of the earths surface: 7%7%</p></li><li><p>Electromagnetic RadiationElectromagnetic Radiation</p><p> The atmosphere is generally transparent to The atmosphere is generally transparent to shortwave radiation and opaque to longwaveshortwave radiation and opaque to longwave</p><p>THE GREENHOUSE EFFECTTHE GREENHOUSE EFFECT</p></li><li><p>Vertical Distribution of the Atmosphere</p></li><li><p>The TroposphereThe Troposphere</p><p> Layer of the atmosphere in contact with the surfaceLayer of the atmosphere in contact with the surface Temperature decreases with height because the Temperature decreases with height because the </p><p>tropospheretroposphere is heated from below (atmosphere is is heated from below (atmosphere is generally transparent to shortwave radiation)generally transparent to shortwave radiation)</p><p> Layer that contains all weather and all cloudsLayer that contains all weather and all clouds Extends to about 12 to 15 km; actual height varies with Extends to about 12 to 15 km; actual height varies with </p><p>latitude and season (thicker as temperature increases)latitude and season (thicker as temperature increases) Much water vapor and dust from interactions with Much water vapor and dust from interactions with </p><p>the surfacethe surface</p><p> Contains about 80% of the mass of the atmosphereContains about 80% of the mass of the atmosphere</p></li><li><p>Vertical Distribution of the AtmosphereVertical Distribution of the Atmosphere</p></li><li><p>The TropopauseThe Tropopause</p><p> Small, isothermal layer above the troposphereSmall, isothermal layer above the troposphere</p><p> IsothermalIsothermal no temperature change with height no temperature change with height</p><p> About 12 to 15 km in height actual height varies with About 12 to 15 km in height actual height varies with latitude and seasonlatitude and season</p></li><li><p>Vertical Distribution of the AtmosphereVertical Distribution of the Atmosphere</p></li><li><p>The StratosphereThe Stratosphere</p><p> Layer of the atmosphere above the troposphereLayer of the atmosphere above the troposphere Temperature increases with height because of Temperature increases with height because of </p><p>absorption of ultraviolet light by ozone (Oabsorption of ultraviolet light by ozone (O33)) Extends up to about 50 km in heightExtends up to about 50 km in height Little exchange of air between troposphere and Little exchange of air between troposphere and </p><p>stratosphere little dust or water vaporstratosphere little dust or water vapor</p><p> Stable air layer little vertical motions because of the Stable air layer little vertical motions because of the increasing temperature with height -- increasing temperature with height -- inversioninversion</p></li><li><p>Vertical Distribution of the AtmosphereVertical Distribution of the Atmosphere</p></li><li><p>The StratopauseThe Stratopause</p><p> Small, Small, isothermalisothermal layer above the stratosphere layer above the stratosphere Isothermal no temperature change with Isothermal no temperature change with </p><p>heightheight</p><p> About 50 km in heightAbout 50 km in height</p></li><li><p>Vertical Distribution of the AtmosphereVertical Distribution of the Atmosphere</p></li><li><p>The MesosphereThe Mesosphere</p><p> Layer of the atmosphere above the stratosphereLayer of the atmosphere above the stratosphere</p><p> Temperature decreases with height because of a lack Temperature decreases with height because of a lack of contact with the ground and a lack of ozoneof contact with the ground and a lack of ozone</p><p> Extends up to about 80 km in heightExtends up to about 80 km in height</p></li><li><p>Vertical Distribution of the AtmosphereVertical Distribution of the Atmosphere</p></li><li><p>The MesopauseThe Mesopause</p><p> Small, isothermal layer above the mesosphereSmall, isothermal layer above the mesosphere</p><p> Isothermal Isothermal no temperature change with height no temperature change with height</p><p> About 80 km in heightAbout 80 km in height</p></li><li><p>Vertical Distribution of the AtmosphereVertical Distribution of the Atmosphere</p></li><li><p>The ThermosphereThe Thermosphere</p><p> Layer of the atmosphere above the mesosphereLayer of the atmosphere above the mesosphere Temperature increases with height because of energy Temperature increases with height because of energy </p><p>from gamma and x-ray absorption due to the earths from gamma and x-ray absorption due to the earths magnetic field (van Allen radiation belt)magnetic field (van Allen radiation belt)</p><p> Density of air at this altitude is very thin and the Density of air at this altitude is very thin and the thermosphere holds little heatthermosphere holds little heat</p><p> Thermosphere essentially drifts off to nothingness Thermosphere essentially drifts off to nothingness above about 120 kmabove about 120 km</p></li><li><p>Lapse Rates:Lapse Rates:</p><p>Temperature decreases with increasing altitude within the Temperature decreases with increasing altitude within the troposphere at an average rate of 6.4 C/kmtroposphere at an average rate of 6.4 C/km</p><p>6.4 C/km = Normal Lapse Rate6.4 C/km = Normal Lapse Rate</p><p>The actual decrease in temp, or actual lapse rate may vary The actual decrease in temp, or actual lapse rate may vary considerably from the normal lapse: considerably from the normal lapse: environmental lapse environmental lapse raterate</p></li><li><p>PollutionPollution</p></li><li><p>The atmosphere is made up of two zones based in function: The atmosphere is made up of two zones based in function: to remove harmful wavelengths of solar radiation and charged to remove harmful wavelengths of solar radiation and charged </p><p>particlesparticles</p><p>IonosphereIonosphere</p><p> Extends throughout the Extends throughout the thermopause and into thermopause and into underlying mesosphereunderlying mesosphere</p><p> Absorbs cosmic rays, gamma Absorbs cosmic rays, gamma rays, x-rays, and shorter rays, x-rays, and shorter wavelengths of UV radwavelengths of UV rad</p><p> Absorption changes atoms to Absorption changes atoms to +ve charged ions ~ ionosphere+ve charged ions ~ ionosphere</p><p>OzonosphereOzonosphere</p><p> ozone layer that is within the ozone layer that is within the stratosphere that contains Ostratosphere that contains O33</p><p> Highly reactive to oxygen Highly reactive to oxygen moleculesmolecules</p><p> Ozone is harmful to living Ozone is harmful to living creatures when present near the creatures when present near the surfacesurface</p><p> Is necessary as absorbs harmful Is necessary as absorbs harmful wavelengths of UV rad and wavelengths of UV rad and reradiates it as safer LW radreradiates it as safer LW rad</p></li><li><p>Ozone DepletionOzone Depletion</p><p>CFCs- ChloroflurocarbonsCFCs- Chloroflurocarbons</p><p>-became widely used in the 1920s for industry-became widely used in the 1920s for industry-valuable as propellants for aerosol sprays and as refrigerants-valuable as propellants for aerosol sprays and as refrigerants-also used in industry as solvents and foaming agents-also used in industry as solvents and foaming agents</p><p> Good for industry as were not flammableGood for industry as were not flammable Cannot be broken down by atmospheric processes near the earths Cannot be broken down by atmospheric processes near the earths </p><p>surfacesurface Not water soluble and do not break down by biologic processesNot water soluble and do not break down by biologic processes Can be broken down by UV radiation within the stratosphereCan be broken down by UV radiation within the stratosphere</p><p>-CFCs migrate to the stratosphere over time-CFCs migrate to the stratosphere over time</p></li><li><p>Breakdown of CFCs from UV radiationBreakdown of CFCs from UV radiation</p><p> Separates single Cl atoms or chlorine monoxide (ClO) Separates single Cl atoms or chlorine monoxide (ClO) molecules from the CFC componentsmolecules from the CFC components</p><p> Ozone is an unstable molecule (OOzone is an unstable molecule (O22 or O or O33)) Chlorine is a catalyst for the destruction of ozoneChlorine is a catalyst for the destruction of ozone</p><p> One Cl atom can decompose 100,000 ozone moleculesOne Cl atom can decompose 100,000 ozone molecules Cl atoms have a residence time within the ozone layer of 40-100yrs.Cl atoms have a residence time within the ozone layer of 40-100yrs.</p><p>Example of ozone breakdownExample of ozone breakdown</p></li><li><p>1970s1970s noticed depletion in levels of ozone, studies into the noticed depletion in levels of ozone, studies into the effect of chemicals on ozone depletioneffect of chemicals on ozone depletion</p><p>19781978 US banned CFCs in aerosols but was still used in US banned CFC...</p></li></ul>

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