Weather Ch13

• Atmosphere


  A thin layer of gases that surrounds the Earth
• Gases in the Earth's atmosphere

  • Nitrogen (78%)
  • Oxygen (21%)
  • Other gases (1%)
• Atmosphere


  • Insulates the Earth from extreme temperatures
  • Traps heat
  • Protects the Earth from dangerous rays from the sun
• Layers in the Earth's atmosphere

  • Troposphere
  • Stratosphere
  • Ozone layer
• Troposphere


  Lowest layer in the Earth's atmosphere, reaches from ground or water level up to about 17 km, weather and clouds occur in this layer
• Stratosphere


  Layer above the troposphere, extends from 17 km to 50 km from the Earth's surface, ozone layer is located in this layer
• Altitude


  Height above sea level
• The temperature generally decreases as the altitude increases
• The Earth's atmosphere is about 480 km thick, but most of it is within 16 km of the Earth's surface
• Solar energy


  Energy from the sun
• Solar radiation


  Energy that travels through space from the sun, transmitted in the form of light and heat
• Almost all of the energy that the Earth uses comes from the sun
• The amount of heat kept in the atmosphere depends on the amount of greenhouse gases in the atmosphere
• How solar radiation heats the atmosphere

  • 30% reflected back from the clouds
  • 19% absorbed by the clouds
  • 51% absorbed by the Earth
• Latitude


  Lines around the Earth that measure distance from the equator
• The equator is closest to the sun, so areas closer to the equator are warmer than areas closer to the poles
• The sun's rays have a shorter distance to travel to the equator so the heat is more intense here than at higher latitudes
• The sun's rays shine directly on the equator and so are concentrated on a smaller area, the rays at higher latitudes are slanted and therefore cover a larger area and are less intense
• The Earth spins on its axis every 24 hours and orbits the sun every 365 days, during this time different parts of the Earth's surface are tilted towards the sun, influencing the seasons and the length of the day and night
• During our summer, the northern hemisphere is tilted towards the sun, days are long and we receive more solar radiation
• During our autumn, the northern hemisphere begins to tilt away from the sun, days get shorter and temperatures drop as we receive less solar radiation
• During our winter, the northern hemisphere is tilted away from the sun, days are short and temperatures are low because there is little solar radiation
• During our spring, the northern hemisphere begins to tilt towards the sun again and days grow longer, temperatures increase with more solar radiation
• Wind


  The movement of air over the surface of the Earth
• Winds blow from areas of high pressure to areas of low pressure
• At the equator, warm air rises creating areas of low pressure, at about 30° north and south of the equator, the warm air begins to cool and sink creating areas of high pressure
• Trade winds


  Warm, steady breezes that blow almost continuously towards the equator
• Coriolis effect


  The rotation of the Earth on its axis causes the trade winds to appear to curve towards the west
• Doldrums


  An area of calm weather near the equator where the trade winds from the north and south meet and rise
• Prevailing westerlies


  Winds that move towards the poles and appear to curve to the east
• Horse latitudes


  A belt of weak winds found at 30° north and south of the equator, between the trade winds and the prevailing westerlies
• Polar easterlies


  Winds that form when the atmosphere over the poles cools, the cool air sinks and spreads over the surface, turning to the west due to the Coriolis effect
• Winds are named after the direction from which they come
• Ocean current


  The movement of water in the ocean, like a river flowing through the ocean
• Gulf Stream


  A warm ocean current that flows from the Caribbean towards Europe
• North Atlantic Drift


  A continuation of the Gulf Stream that flows towards northern Europe
• Labrador Current


  A cold ocean current that flows from the Arctic towards the east coast of North America
• Ocean currents occur due to differences in temperature, the Earth's rotation, and wind
• Do winds blow from areas of high pressure to low pressure or from low pressure to high pressure


  Winds blow from areas of high pressure to low pressure
• Which winds are cooler in Ireland? Polar easterlies or prevailing westerlies

  Prevailing westerlies are cooler in Ireland. This is because the prevailing westerlies bring warm, moist air from the Atlantic Ocean, while the polar easterlies bring cold, dry air from the Arctic.