GEOG141 Lecture 2
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This 5 page Class Notes was uploaded by Wei Yeen on Monday February 9, 2015. The Class Notes belongs to GEOG141 at University of Oregon taught by Matthew Goslin in Fall. Since its upload, it has received 147 views.
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Eugh...this class is soo hard! I'm so glad that you'll be posting notes this semester.
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Date Created: 02/09/15
GEOG141 Lecture 2 ANNOUNCEMENT Use iClickers on next Monday rst class of the week On Blackboard the textbook reading guide tells you which special boxes in the text should be read and skipped Review of Last Lecture Map Projections the representation of spherical earth as a at surface Tradeoffs between true representation of shape direction distance and area 0 The Mercator projection retains the direction 0 The Robinson projection retains area 0 The Peters projection cylindrical but has continents of countries retains area Google Maps use the web Mercator projection lt preserves shape when you zoom in Chapter 2 Solar Energy to Earth and the Seasons Movement of earth around the sun 2 Aspects 1 Revolution Completes one every 365 14 days Counterclockwise o Elliptical orbitsun is not in the middle of the plane of the ecliptic Aphelion when earth is furthest away from sun july 4 summer here Perihelion when earth is closest to the sun january 3 winter here 2 Rotation Rotates eastward around NS axis counter clockwise 1 rotation 360 degrees every 24 hours Rotational velocity equator 1660 km per hour 60 830 km per hour 0 Earth39s rotational axis is inclined 23 12 to the plane of the ecliptic IT IS TlLTED 3 Parallelism Earth39s axis points same way as it revolves around the sun Insolation incoming solar radiation how we describe energy coming from the sun varies by latitude and by season units of watts per square meter Wm2 Insolation at different angles the angle of the sun39s energy determines intensity of insolation on the ground if insolation is spread out over a larger area density of insolation intensity is lower over that area if the sun is hitting the earth at a 90 angle 1 unit of light is concentrated over 1 unit of surface area if the sun is hitting the earth at a 45 angle 1 unit of light is concentrated over 14 units of surface area if the sun is hitting the earth at a 30 angle 1 unit of light is concentrated over 2 units of surface area annually you get 25 more energies at the equatorpoles Energy Distribution over Earth Subsolar point point of earth39s surface directly perpendicular to sun39s rays 90 the shadow is directly beneath the person All other points receive sunlight at an angle lt 90 oblique Seasonality Five Reasons Why Tilted axis Rotation on its axis Axial parallelism Shape sphere Revolution around sun U39lbUUNH Key seasonal dates Equinoxes equal hours of days and nights March 21 September 21 Solstices most extreme points in seasonality June 21 December 21 The four seasons occur because the earth maintains constant orientation tilted 23 12 as it revolves around the sun June Solstice Sun directly overhead the Tropic Of Cancer 235 N 24 hours of sunlight above Arctic Circle 665 N Longest day of the year in the N Hemisphere Shortest day in the S Hemisphere December Solstice Sun directly overhead Tropic of Capricorn 235 S 24 hrs sunlight below Antarctic Circle 665 S Longest day of the year in S Hemisphere Shortest day of the year in N Hemisphere Equinoxes Sun directly overhead the Equator Equal day and night everywhere 12 hours of each NOT the reasons for the seasons Earth39s changing distance of the sun Earth doesn39t wobble back and forth from summer to winter doesn39t change its axis of tilt lnsolation is dependent on the directness of radiation and duration of radiation Latitude of subsolar point is the sun39s declination angle Average lnsolation Across Latitudes Polar extreme highlow duration indirect radiation LOW INSOLATION MidLatitude seasonal duration season directness MEDIUM INSOLATION Tropic equal duration direct radiation HIGH INSOLATION Chapter 3 Earth39s Modern Atmosphere Goal Understand a model of the atmosphere based on Composition 0 Temperature 0 Function Earth39s atmosphere Gaseous layer surrounding earth 0 Provides carbon dioxide water vapor oxygen Serves as insulator maintaining temperatures Atmospheric air pressure Denser at earth39s surface Gravity pulls molecules down the closer you are to earth the stronger gravity is The percentages of gases such as oxygen don39t change but as you go up in elevation or altitude the pressure becomes less because there is less absolute oxygen per space Atmosphere Layers can be de ned by composition temperature function 1 3 Composition Heterosphere upper portion strati ed into major chemical components sorted by atomic weight Homosphere lower portion homogenized Constant gases in the Homosphere nitrogen 78 oxygen 21 argon 093 Other atmospheric elements are carbon dioxide ozone water vapor helium hydrogen FuncUon lonosphere Upper layer blocks shortwave radiation by changing atoms into positive ions Ozonosphere Lower layer high concentration of ozone in this layer absorbs dangerous UV radiation Temperature Thermosphere highest layer starts cold but climbs to as much as 1100 C 2000 F corresponds with heterosphere Mesosphere coldest warmest at lowest point boundary with stratosphere meteor dust here beginning of homosphere Stratosphere atmosphere ozone is here temperature rises from boundary with troposphere below to top of stratosphere Troposphere lowest layer all weather life on earth temperatures drop at constant rate with increasing altitude until boundary with stratosphere environmental lapse rate 65 C1000m Within the atmosphere the variable components are important Carbon Dioxide 00393 or 393 ppm parts per million Methane 000014 or 14 ppm Nitrous Oxide Ozone Carbon Monoxide Sulfur Oxides Hydrogen Sul tes Dust particulates pollens Water vapor Volcanoes produce water vapor carbon dioxide sulfur oxides particulates critical to our composition Forest res produce carbon monoxide carbon dioxide nitrogen oxides and particulates Soil windstorm produce dust viruses Living Plants hydrocarbons poens Decaying Plants methane hydrogen sul des Ocean salt spray particulates Anthrooooenic alterations and quotcontributionsquot to atm05phere ie pollution Greenhouse gases include carbon dioxide methane mostly from enteric fermentation or from animals nitrous oxide F gases contain chloro uorocarbons 0 Ozone depletion DE jeky and Mn Hyde of the atmosphere The GOOD Ozone in the stratosphere helps block UV radiation Ozone39s enemy is chloro uorocarbons THE BAD Ozone in the troposphere triggered by UV radiation and photochemical reactions reacting with Nitrogen Dioxide which is product from car exhaust producing photochemical smog Urban photochemical smog Industrial smog and sulfur oxides acid rain Pollution Natural Factors 0 Temperature inversions Topography
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