Global Systems

Daily Web Guide

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Reading Assignment	Browse through the Audubon Field Guide to the Weather pp. 65-66, 68, 42-43. Complete the "Racing Eastward" worksheet as a homework assignment, and turn it in as part of your first journal (due Feb. 20).
Reminders	The meteorological journal web page now offers a revised template you can use for your observations. Copies are available in my office or on the web. Fill out five to put in your journal every two weeks.

Class notes

Atmosphere

• Rare cocoon of life
• What is the most abundant gas in our atmosphere?
• Nitrogen, N2 = 78%
• Oxygen, O2 = 21%
• Trace amounts: Carbon dioxide, CO2 and Water vapor, H2O

Troposphere

• Turbulent, scene of "weather"
• Lowest layer
• 12 miles high at equator, 5 miles at poles; 10 miles average
• Ceiling: tropopause, temperature no longer decreases with altitude

Stratosphere

• Layer directly above troposphere
• 6 - 30 miles
• Temperature may increase with altitude
• Ozone layer
  • Absorbs harmful UV radiation
  • Broken down by CFC's (chlorofluorocarbons)
• Volcanic dust

Outer layers

• Mesosphere, 30 - 50 miles
• Thermosphere, 50 - 120 miles
• Ionosphere, 120 - 250 miles
  • air molecules/atoms ionized (charged)
  • aurora borealis (northern lights)
  • reflects radio waves for long-range reception

Aurora borealis, "northern lights"

• Aurora australis, "southern lights"
• Solar winds
• Ionized particles at millions of miles per hour, reach Earth in about 30 hours
• Max. correlates with 11 yr. sunspot cycle
• Deflected to poles by Earth's magnetic field
• Magnetic storms, atoms in ionosphere
• March 13, 1989: Quebec power blackout

Why does the weather change?

• Regional factors and topography
  • Rocky Mountains
  • Gulf of Mexico
  • El Niño ocean currents
• Heat from the sun
• Motion of the Earth
  • Annual &endash;> seasons
  • Diurnal &endash;> day and night

What causes the seasons?

• Seasons: Is the Earth closer to the sun in summer?
• Ecliptic
  • Path of the Sun against the stars
  • Plane of Earth's orbit
  • Is the ecliptic the same circle as the equator?
  • What is the angle between the ecliptic and the equator?
• Equinoxes
  • March 21 and September 21
  • Sun directly over equator
  • Equal daylight and nighttime
• Solstices
  • December 21 and June 21
  • Sun directly over tropic of Cancer or Capricorn
  • Longest day or longest night

Diurnal motion of the Earth

• How fast is someone at the Earth's equator racing eastward?
  • Circumference: 24,000 miles
• How fast are we racing eastward at OBU? (Racing Eastward worksheet)
• Coriolis effect (AFG, p. 28)
  • As currents/winds move toward the poles they race eastward faster (like spinning ice skater)
  • Systems rotate clockwise in north hemisphere