Chapter 2 Notes
Chapter 2 Notes Geog 1112
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This 3 page Class Notes was uploaded by Alexandra Reshetova on Sunday January 17, 2016. The Class Notes belongs to Geog 1112 at Georgia State University taught by Aneela Qureshi (P) in Spring 2016. Since its upload, it has received 106 views. For similar materials see INTRO TO WEATHER & CLIMATE in Geography at Georgia State University.
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Date Created: 01/17/16
Chapter 2: Solar Energy to Earth and the Seasons The Solar System, Sun, and Earth Milky Way Galaxy – flattened, disk shaped collection of stars in the form of a barred- spiral (a spiral with a slightly barred, or elongated core) Our Solar System – located more than halfway out from the galactic center; one of the Milky Way’s spiral arms – the Orion Spur of the Sagittarius Arm Our Solar System – 8 planets, 4 dwarfs, asteroids Middle of Galactic Center: super massive black hole named Sagittarius A Star Solar System Formation Nebula Gravity = the mutual attraction exerted by every object upon all other objects in proportion to their mass Protosun Protoplanets Planetesimal Hypothesis (Dust Cloud Hypothesis) = explains how suns condense from nebular clouds Dimensions and Distances Speed of Light = 300,000 kmps (kilometers per second) Light year: unit of measurement for the universe Perihelion = Earth’s closest position to the Sun Aphelion = Earth’s farthest position to the Sun Structure of Earth’s orbit: changes over long periods Solar Energy: From Sun to Earth Sun = got 99.9% of matter form solar nebula; has a big enough mass to sustain a nuclear reactor in its core and make radiant energy Fusion = when hydrogen atoms are forced together and pairs of hydrogen nuclei are joined In Fusion Reaction: hydrogen nuclei form helium; a lot energy is freed (Disappearing solar mass becomes energy) Solar Wind Electromagnetic Spectrum Solar Activity and Solar Wind Solar Cycle 1800’s = telescopes allows sunspot observation Sunspots Solar Disturbances caused by magnetic storms Solar Minimum = period when few sunspots are visible Solar Maximum = period when sunspots are numerous; sun activity the highest Solar Flares = magnetic storms that cause surface explosions Prominence Eruptions = outbursts of gases arcing from the surface; near sunspots Solar Wind Effects Solar Wind Magnetosphere Auroras Electromagnetic Spectrum of Radiant Energy Electromagnetic Spectrum = the spectrum of all possible wavelengths of electromagnetic energy Wavelength = the distance between corresponding points on any two successive waves Frequency = the number of waves passing a fixed point in 1 second Law to know: all objects radiate energy in wavelengths related to their individual surface temperatures (holds true for Sun and Earth) Blackbody = perfect absorber of radiant energy Sun (hotter object) emits a lot more energy than Earth (cooler object) Earth acts as a blackbody Earth = emits longer wavelengths (mostly in the infrared portion) Sun’s radiated energy = shortwave radiation Earth’s radiated energy = longwave radiation Incoming Energy at the Top of the Atmosphere Thermopause = the region at the top of the atmosphere Insolation = solar radiation that is intercepted by Earth (measured as watts per square meter or W/m^2) Solar Constant Solar Constant = the average insolation received at the thermopause when Earth is at its average distance from the Sun (value of 1372 W/m^2) Uneven Distribution of Insolation Subsolar Point = the point where insolation comes perpendicular to the surface; happens only at lower latitudes between the tropics Global Net Radiation Net Radiation = the balance between incoming shortwave energy fromteh Sun and all outgoing radiation from Earth and the atmosphere (energy inputs minus energy outputs) Isolines = lines connecting points of equal value The Seasons Ancient Societies = displayed awareness of seasonal changes Seasonality Altitude = the angle between the horizon and the sun Declination = the latitude of the subsolar point Daylength = the duration of exposure to insolation Sunset = the moment when it completely disappears below the horizon in the west Reasons for the Seasons (Look at Table 2.2 on page 51) Seasons result from = Sun’s altitude, Sun’s declination, and daylength of the year Those results are made by 5 physical factors such as: 1. Earth’s revolution around the sun 2. Earth’s rotation of its axis 3. Earth’s tilted axis 4. Earth’s unchanging orientation of its axis 5. Earth’s sphericity Revolution Earth’s speed in orbit = about 107,280 kmph About 107,280 kmph and Earth’s distance from Sun = determines the time required for one revolution around the sun ( also determines the duration of seasons and length of a year) 365.2422 days = Earth completes annual revolution Tropical year = measured from equinox to equinox; the 365.2422 number is based on this Rotation Rotation = turning on axis Earth’s rotation = averages slightly less than 24 hours in duration Rotation: 1. Determines daylength 2. Makes the deflection of winds and ocean currents 3. Produces ocean tides Axis = an imaginary line extending through the planet from the geographic North Pole to the South Pole Circle of Illumination = the dividing line between day and night Tilt of Earth’s Axis Axial Tilt Plane of the Ecliptic Axial Parallelism Axial Parallelism - Axis looks parallel to itself Sphericity Earth’s spherical shape = causes the parallel rays of the sun to fall at uneven angles on Earth’s surface Annual March of the Seasons The extremes of daylength = June and December December 21, June 21 = solstices Tropic of Cancer Tropic of Capricorn December Solstice = Northern Hemisphere winter solstice Arctic Circle = the southernmost parallel that experiences a 24 hour period of darkness March Equinox (Vernal Equinox) June Solstice = summer solstice in the Northern Hemisphere Antarctic Circle September Equinox (Autumnal Equinox) Dawn and Twilight Dawn = the period of diffused light that happens before sunrise Twilight = the corresponding evening time after sunset Light is scattered and reflected during these periods The extent of both periods = function of latitude At equator = dawn and twilight last 30-45 minutes
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