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Ch.17 Notes Mc Neely 2009
 

Ch.17 Notes Mc Neely 2009

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    Ch.17 Notes Mc Neely 2009 Ch.17 Notes Mc Neely 2009 Presentation Transcript

    • The Atmosphere Ch. 17 Earth-Space Science Bremen High School Teacher : Aaron McNeely
    • Weather and Climate (Sec 17.1)
      • Earth’s Atmosphere:
        • The gases that surround the earth
        • Where weather occurs
      • Weather : The state of the atmosphere at a given place or time
      • Climate is based upon observations of weather over many years
      • Climate helps describe a place or region
    • Composition
      • Air is a mixture of different gases and particles
      • Contents:
        • Nitrogen (78%)
        • Oxygen (21%)
        • Argon and others (1%)
    • Slice of Atmosphere? 1% CO 2 , Argon, Others 21% Oxygen 78% Nitrogen
    • Other Components
      • Water vapor, source of all clouds and precipitation
      • Ozone, form of oxygen (O 3 ) that protects surface from sun’s ultraviolet light
    • Pollution
      • Artificial gases and particles placed into the atmosphere
      • About half consists of automobile exhaust
    • Height of the Atmosphere
      • Thins rapidly with height, also pressure
      • Atmospheric pressure is the actual weight of the atmosphere resting over your head
      • Rapid change in elevation can create uncomfortable pressure changes (ear popping)
    • Pressure vs. Altitude (height)
      • Pressure lies along the bottom axis, altitude along the vertical
      • Below how many miles is roughly half of the atmosphere?
    • Atmospheric Layers
      • The atmosphere is divided into four vertical layers based upon temperature changes
      • 4 Layers :
        • Troposphere
        • Stratosphere
        • Mesosphere
        • Thermosphere
      http://www.epa.gov/air/oaqps/eog/course422/images/fig-1.gif
    • Troposphere
      • Bottom layer
      • Temperature decreases with height
      • Height : 0-7 miles
      • Tropopause : Boundary between troposphere and stratosphere
      • Where most of our weather occurs
    • Stratosphere
      • Second layer
      • Temperature remains constant, then increases with height
      • Height : 7-30 miles
      • Stratopause : Boundary between the stratosphere and mesosphere
      • The “ozone layer” lies at a height of 15 miles within the stratosphere
    • Mesosphere
      • Third layer of the atmosphere
      • Temperature decreases with height
      • Height : 30-50 miles
      • Mesopause : Boundary between the mesosphere and Thermosphere
    • Thermosphere
      • Lat layer, gradually merges into outer space
      • Temperature increases with height
      • Height : 50-90 miles
      • The aurora or northern lights occur in the thermosphere
    • Atmospheric Temperature Change
      • Temperature lies along the bottom axis, height along the vertical
      • The behavior of temperature defines each of the atmospheric layers
    • Layers Summary
      • Select the appropriate letter in the figure to the right that identifies each of the following layers of the atmosphere:
      • _____ mesosphere
      • _____ troposphere
      • _____ thermosphere
      • _____ stratosphere
    • Earth-Sun Relationships
      • Earth’s Motions : Earth has two principal motions:
        • Rotation : Earth’s 24 hour spin on its axis, results in the day
        • Revolution : Earth’s 365 day journey around the sun, results in the year
    • Rotation & Revolution http://geography.uoregon.edu/shinker/geog101/lectures/lec02/lec02_figs/Earth-revolution-and-rotation-fig2-13.gif
    • Earth’s Seasons http://www.uwsp.edu/geo/faculty/ritter/images/atmosphere/energy/earth_orientation_small.jpg Northern hemisphere directed towards the sun Northern hemisphere directed away from the sun
    • Seasons
      • The seasons begin with events named solstices and equinoxes
      • Winter and Summer, the most extreme of the seasons, are solstices
      • Spring and Autumn, the “middle” seasons, are equinoxes
    • Season Summary Tropic of Capricorn (-23.5) Winter (N) Summer (S) Dec 21 Solstice Equator (0) Autumn (N) Spring (S) Sept 21 Equinox Tropic of Cancer (+23.5) Summer (N) Winter (S) June 21 Solstice Equator (0) Spring (N) Autumn (S) Mar 21 Equinox Sun Overhead (latitude) Season (North & south) Event
    • Seasons Summary
      • Select the appropriate letter in the figure below that identifies each of the following months:
      • _____ March
      • _____ June
      • _____ December
      • _____ September
    • Earth’s Orientation & Seasons
      • Earth tilted 23.5° compared to the sun
      • Earth’s axis tilted compared to its orbit
      • Tilt results in the northern and southern hemispheres of earth each being directed toward the sun at different times during the year
      • Tilt is cause of earth’s seasons
      • Axis will always point to the star Polaris (North Star) in our lifetimes
    • Earth’s Tilted Axis
      • Geography: Seasons
    • Length of Day & Night
      • Changes due to earth’s tilt and revolution
      • Equinoxes, both day and night are 12 hours
      • Summer solstice, more hours of day, less of night
      • Winter solstice, less hours of day, more of night
    • Day & Night Hours http://odin.physastro.mnsu.edu/~eskridge/astr101/day_night.jpg Midnight Noon Days
    • Earth’s Tropics
      • The two Tropics lie 23.5 ° north and south of the equator
      • Latitudes where the noon sun is directly overhead during summer and winter
      • At the equinoxes, the noon sun lies directly overhead at the equator
    • Arctic & Antarctic
      • Arctic and Antarctic circles both lie 90°-23.5° = 66.5° north and south
      • Areas greater in latitude of the circles can experience 24 hours of day and night depending on the seasons
    • Tropics and Circles
    • Equinoxes
    • Planetary Positions
      • In elliptical orbits
      • Perihelion : Position closest to sun
      • Aphelion : Position farthest from sun
      • Earth
        • Perihelion: Jan 02
        • Aphelion: July 04
    • Elliptical Orbit (Keplerian) Sun Earth Oval in diagram is very exaggerated, earth’s orbit is close to circular
    • Earth’s Revolution
      • At perihelion, earth revolves faster in its orbit, slower at aphelion
      • Sun’s apparent size changes slightly as a result
    •  
    • Close and Far
    • Climate Factors (Sec 17.3)
      • The main determinant of climate is latitude
      • Closer to equator, warmer climate
      • Other:
        • Large bodies of water
        • Altitude
        • Cloud cover
        • Ocean currents
    • Land and Water
      • Land heats rapidly and to higher temperatures compared to water
      • Land also cools rapidly and to lower temperatures than water
      • Marine locations have a nicer climate
      • Southern Hemisphere : More ocean than land creates moderate climates
    • Ocean vs. Land
    • Hemispheres N S E W
    • Altitude
      • Higher elevations experience a cooler climate compared to locations near sea level
    • High and Low Altitude
    • Cloud Cover
      • Albedo : The fraction of total radiation that is reflected by a surface
      • Clouds have high albedos
      • Cloud cover creates a cooler day, a warmer night
      • In day, clouds provide shade
      • At night, clouds prevent the heat from escaping into space
    • Cool Days, Warm Nights Cloudy skies create cooler days and warmer nights
    • Urban Heat Islands
      • Cities are often 6-8 º warmer than surrounding countryside
      • Reasons:
        • Less green plants
        • Concrete structures and roads absorb heat, release slowly at night
    • Wash DC Urban Heat Island
    • Urban Heat Island Profile
    • World Temperatures
      • Isotherms are lines on a weather map connecting points of equal temperature
      • Temperatures generally range east to west, parallel to latitude
      • Temps decrease from equator to poles
    • Isotherms
      • The lines generally trend west to east, and cooler from south to north
      http://www.learner.org/jnorth/images/graphics/u-z/weather_isotherm030201.gif
    • Ocean Isotherms https://www.fnmoc.navy.mil/products/OTIS/US058VMET-GIFwxg.OTIS.glbl_sst.gif