Global Atmospheric Circulation

• Define weather

  Day to day conditions of our atmosphere
• Define climate

  Long term changes in the earth's climate
• What is global atmospheric circulation?

  • In our atmosphere, there's a mass of gas above our heads.
  • Heat radiation from the sun is absorbed by clouds.
  • At higher latitudes, the radiation is spread out across a larger surface, so it is colder.
  • Snow, ice, and thick clouds reflect the sun's radiation back into space
• Define the albedo effect

  Light surfaces reflect heat, dark surfaces absorb heat, so snow and ice reflect heat.
• Define latitude

  Distance from the equator
• Summary of global atmospheric circulation

  • Air travels from high to low
  • High pressure = Air falls = Clear skies and deserts
  • Low pressure = Air rises = Clouds form rainfall
  • Trade winds - Winds move towards the equator due to low pressure.
• Define air pressure

  Air travels from high to low pressure as hot air is less dense
• What type of weather does low pressure create

  Cloudy and rainy as it's less dense so air rises, cools, and condenses
• What type of weather does high pressure bring and why?

  Dry, clear skied desserts as it is more dense and so air sinks
• Name an area that experiences high pressure

  The poles and the sahara desert
• Name an area that experiences low pressure

  The UK and Rainforest biomes
• Why is the tilt and rotation of the earth important

  Polar regions don't see day light in the winter
• Hadley cells

  • First climate cycle cell on Earth.• Starts at equator, heats ground, creates low-pressure zone.• Cools and forms cumulonimbus clouds.• Separates and moves north and south towards poles.• Sinks towards ground, creating subtropical high-pressure zone.• Warms and dries, creating deserts.• Completes with air flowing back towards equator as trade winds.
• Ferrel Cells

  • The Ferrel cell occurs at higher latitudes, where surface air is pulled towards the poles.• Warm south-westerly winds form in the northern hemisphere and north-westerly winds form in the southern hemisphere.• These winds pick up moisture as they travel over the oceans.• At 60 degrees N and 60 degrees S, they meet cold polar air drifting from the poles.• The lighter, warmer air from the tropics rises, causing low pressure and unstable weather conditions.
• Polar Cells

  • At the poles, air is cooled and sinks towards the ground forming high pressure, this known as the Polar high. It then flows towards the lower latitudes. At about 60 degrees N and S, the cold polar air mixes with warmer tropical air and rises upwards, creating a zone of low pressure called the subpolar low. The boundary between the warm and cold air is called the polar front. It accounts for a great deal of the unstable weather experienced in these latitudes
• Explain how the global atmospheric circulation affects the weather and climate of the tropics (6)

  • Movement of pressure belts = experienced distinct seasons
  • Northern summer = Northern hemisphere experience south westerlies
  • Southern summer = Northern easterlies
  • Wind blows on shore = Wet season
  • Off shore north easterlies = Dry season
  • South east trade winds dry where blow off shore on west side of continents in southern hemisphere
  • Weather in tropics uniformly hot with small temp range as sun is always high
  • Dry season may have higher temps due to lack of clouds