chapter 8.1

• Seasons


  The cycle of changes in the weather and temperature that occur over a year
• Earth's orbit and rotation

  1. Takes one year to orbit the Sun

  2. Rotates on its axis every 24 hours

  3. Axis is tilted at 23.5 degrees
• Tilt of Earth's axis


  • Causes the Sun's rays to fall more directly on the northern and southern latitudes at different times of year
• Sun's vertical rays fall at 23.5 degrees north latitude, summer in northern hemisphere, winter in southern hemisphere


  June 21st
• Sun's vertical rays fall at 23.5 degrees south latitude, winter in northern hemisphere, summer in southern hemisphere

  December 22nd
• Tropics


  The area between the two latitudes where the Sun's vertical rays fall, receives the most solar energy, always warm
• Midsummer night


  At the North Pole, it stays light around June 21st
• Polar night


  At the North Pole, it stays dark around December 22nd
• The Poles are on the line dividing day and night, the Sun is directly above the equator, day and night are equal


  March 21st and September 23rd
• Latitude


  Determines temperature, high latitudes are cold, low latitudes are warm
• The Earth is a sphere


  In the tropics, the Sun's rays hit the surface directly, in polar regions the rays hit diagonally
• Diagonal rays


  Cover a larger surface area, so the heat is spread out more
• Diagonal rays


  Travel farther through the atmosphere, hit more water droplets and dust particles
• Land and water


  Land warms up and cools down faster than water
• Air temperature above land

  Can get very warm and very cold, changes quickly
• Air temperature above sea

  Never very high or very low, moderated by the sea
• Onshore wind


  Blows from the sea towards land
• Offshore wind


  Blows from land towards the sea
• Onshore wind in summer


  Less warm (cooling)
• Onshore wind in winter

  Less cold
• Offshore wind in summer

  Warmer
• Offshore wind in winter

  Colder
• Precipitation


  Water in the atmosphere that falls to the Earth's surface as rain, snow, hail, etc.
• Precipitation formation


  1. Warm air rises and cools, cold air can't hold as much water vapour

  2. Water vapour condenses into droplets or ice particles

  3. Clouds form and precipitation falls
• Precipitation factors


  • Warm air rising against mountains (relief rainfall)
  • Warm air rising at the equator (convectional rainfall)
  • Warm and cold air colliding (frontal rainfall)
  • Coastal location with onshore winds bringing moist air
• Drought


  Caused by descending air that warms up and can hold more water vapour, dissolving clouds
• Deserts are located just north or south of the tropics where descending air creates dry conditions
• Deserts


  • Death Valley, United States
• In the Netherlands, descending air also results in dry weather with high pressure