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Ch03 Ch03 Presentation Transcript

  • Chapter 3: Introduction to theAtmosphereImage courtesy of cimss.ssec.wisc.eduMcKnight’s Physical Geography:A Landscape Appreciation,Tenth Edition, Hess
  • © 2011 Pearson Education, Inc.Introduction to the Atmosphere• Size of Earth’s Atmosphere• Composition of the Atmosphere• Vertical Structure of the Atmosphere• Human-Induced Atmospheric Change• Depletion of the Ozone Layer• Weather and Climate2
  • © 2011 Pearson Education, Inc.Size of Earth’s Atmosphere• Atmosphere uniformlysurrounds Earth• Held down by Earth’sgravity• Extends up to 10,000km from the surface• More than 50% of thetotal mass is below 6 km3Figure 3-2 View slide
  • © 2011 Pearson Education, Inc.Composition of the Atmosphere• Two primary gas types– Permanent• Oxygen and Nitrogen– Variable• Water Vapor• Carbon Dioxide• Ozone• Permanent gases makeup over 95% of totalatmosphere4 View slide
  • © 2011 Pearson Education, Inc.Composition of the Atmosphere• Particulates– Non-gaseous particleswhich exist in theatmosphere– Many human-inducedand natural types– Many are hygroscopic– Some reflect orabsorb sunlight5Figure 3-4
  • © 2011 Pearson Education, Inc.Vertical Structure of theAtmosphere• Thermal Layers– Troposphere—lowest 10-15km of atmosphere; mostweather occurs here– Stratosphere—stagnant air– Mesosphere—middle ofatmosphere– Thermosphere—“heat”– Exosphere—transitions intointerplanetary space6Figure 3-5
  • © 2011 Pearson Education, Inc.Vertical Structure of theAtmosphere• Air Pressure– Analogous to the “weight” ofthe air– Decreases with height atnonconstant rate– Low-levels compressed byair above, so surfacepressure is higher– 90% of atmosphere is inlowest 16 km7Figure 3-8
  • © 2011 Pearson Education, Inc.Vertical Structure of theAtmosphere• Composition– Homosphere—lowest80 km– Heterosphere—aboveheterosphere– Ozone layer—between15 and 48 km;ozonosphere– Ionsophere—between60 and 400 km; sourceof auroras8Figure 3-9
  • © 2011 Pearson Education, Inc.Human-Induced AtmosphericChange• Introduction of impurities into theatmosphere at rapid pace• Received international attention in recentyears• Example is the reduction of ozone by CFCs9
  • © 2011 Pearson Education, Inc.Depletion of the Ozone Layer• Chemistry ofozone depletion10Figure 3-12
  • © 2011 Pearson Education, Inc.Depletion of the Ozone Layer• The “Hole” in theOzone layer• Mainly affects polarregions• The Montreal Protocol11Figure 3-13
  • © 2011 Pearson Education, Inc.Human-Induced AtmosphericChange• Definition• Primary versussecondary pollutants• Primary pollutants– Particulates– Carbon monoxide– Nitrogen compounds– Sulfur compounds• Secondary pollutants– Photochemical smog– Ozone12Figure 3-15
  • © 2011 Pearson Education, Inc.Weather and Climate• Weather—short-termatmospheric conditionsfor a specific area• Meteorology• Climate—aggregatelong-term weatherconditions• Climatology• Weather versus climate13
  • © 2011 Pearson Education, Inc.Weather and Climate• Distinction between continental and maritimeclimates• Seattle, WA, and Fargo, ND, have vastly differentclimates• Maritime climates typically much more humid14
  • © 2011 Pearson Education, Inc.Weather and Climate• General circulation ofthe atmosphere– Semipermanent windpattern on Earth• General circulation ofthe oceans– Oceanic broad-scalesemi-permanentmotions15Figure 3-17
  • © 2011 Pearson Education, Inc.Weather and Climate• Altitude– Four controls ofweather and climateaffected by altitude• Topographic barriers– Can drastically alterclimate due toorographic change inwind patterns16Figure 3-20
  • © 2011 Pearson Education, Inc.Weather and Climate• Storms– Control weather and climatethrough atmosphericmodification– Some storms prominentenough to affect climate17Figure 3-21
  • © 2011 Pearson Education, Inc.Weather and Climate• Coriolis effect– Rotation of Earth modifies path of forward motion overgreat distances– Discovered by Gaspard Coriolis– Causes a rightward turn to motion in the NorthernHemisphere– Causes a leftward turn in the Southern Hemisphere– Deflection greatest at the poles; zero at the equator– Proportional to the speed of the object– Has no influence on speed18
  • © 2011 Pearson Education, Inc.Weather and Climate• Coriolis effect19Figure 3-22
  • © 2011 Pearson Education, Inc.Summary20• Earth’s atmosphere is a shallow “ocean” of airthat uniformly surrounds the Earth• The atmosphere consists of many permanentand variable gases• The gas with the highest concentration inEarth’s atmosphere is nitrogen (78%)• The atmosphere has various vertical structuresthat describe it• Five main spheres make up the thermalatmosphere
  • © 2011 Pearson Education, Inc.Summary21• The homosphere and heterosphere describe thegas composition of the atmosphere at differentheights• Most auroral activity occurs in the ionosphere• Human activity has modified the atmosphericcomposition through pollution and ozonedepletion• Weather and climate, while related, involveatmospheric conditions on different time scales
  • © 2011 Pearson Education, Inc.Summary22• Many controls exist that modify the four primaryweather elements• The Coriolis effect is an apparent force thatexists due to the rotation of Earth