chapters 29-30

• Wind


  Moving air
• How wind is formed

  1. The Earth heats the air above it

  2. The warm air expands, becomes less dense and rises

  3. This causes low air pressure

  4. Air at the top of the troposphere cools, contracts and becomes denser

  5. This makes the cold air fall and causes high air pressure

  6. When the cold air falls, it pushes the warm air

  7. Air always moves from areas of high pressure to areas of low pressure
• Global wind patterns


  Winds blow from areas of high pressure to areas of low pressure, forming a global pattern of winds known as the global winds or prevailing winds
• Wind belt 1


  1. Near the equator, air is heated so it expands and rises, creating a belt of low pressure

  2. This air then moves away from the equator and starts to cool down

  3. At 30° latitude the cool air is heavier and presses down on the Earth, creating a belt of high pressure

  4. The cool air moves along the surface of the Earth back towards the equator to replace warm air that is rising
• Wind belt 2


  1. At 60°, air from 30° warms and rises

  2. This air eventually cools and then moves away from 60°

  3. Some goes to the equator, creating the second wind belt

  4. Some air travels to the poles, helping create the third wind belt
• Wind belt 3


  1. At the North Pole, air from 60° is cold, so it sinks, creating high pressure

  2. This cold air moves away from the poles

  3. At a latitude of around 60° the air is heated, so it expands and rises, creating a belt of low pressure

  4. The warm air moves back towards the North Pole to replace cold air that is sinking
• Air movement


  Moves from areas of high pressure to areas of low pressure
• Pressure belts


  Areas of high and low pressure
• Types of pressure belts

  • The doldrums: low-pressure areas near the equator where wind speeds are very low or winds have died out entirely
  • The horse latitudes: high-pressure areas of still, dry weather at 30° north and 30° south
  • The polar fronts: low-pressure areas of still weather at 60° north and 60° south
• Coriolis effect


  The Earth's rotation causes winds to change direction
• In the northern hemisphere, winds are deflected to the right
• In the southern hemisphere, winds are deflected to the left
• How winds are named


  Winds are named after the direction from which they blow
• If a wind blows from the north towards the south, it is called a northerly wind
• If a wind blows from the south-east, it is a south-easterly wind
• Ireland's prevailing winds are south-westerly winds
• Cloud and cloud typesWhen air becomes saturated it cannot hold any more water vapour. Any extra water vapour condenses into small droplets and forms clouds. There are three main types of cloud: cirrus, cumulus and stratus.
• The water cycle


  1. The sun's energy heats the sea and causes the evaporation of seawater

  2. Water vapour rises as it is light

  3. Water vapour cools and condenses into water droplets forming clouds

  4. Prevailing winds blow clouds towards land

  5. Clouds are forced to rise over land, causing more cooling and condensation

  6. Water droplets combine and fall as precipitation

  7. Water runs off land into rivers and streams, returning to the sea

  8. Some water soaks into the ground and is stored or returned to the sea through bedrock
• Relief rain


  1. Air passes over a warm ocean current and picks up moisture

  2. The warm, moist air blows inland from the sea, and it is forced to rise

  3. As the air rises, it cools and condenses into cloud

  4. Rain eventually falls on the mountain's windward side (facing the wind)

  5. The air then sinks down the leeward (sheltered) side of the mountain
• Relief rain is common in mountainous areas off the west coast of Ireland, such as Donegal and Kerry
• Convectional rain


  1. The sun heats the Earth's surface. Air over the land is warmed and expands

  2. As the air expands, it rises rapidly. The air rises, cools and condenses into droplets

  3. This causes cumulus cloud to form

  4. Convection rainfall often occurs as heavy, thundery showers
• Convectional rainfall is common in areas near the equator. It occurs in Ireland during hot, sunny weather conditions
• Frontal (cyclonic) rain


  1. Cold and warm air masses meet at a front. The light, warm air mass rises up over the heavy, cold air mass

  2. As the warm air rises, it cools and condenses into droplets. This causes stratus cloud to form

  3. Eventually, rain falls. Rain is light at first but becomes heavier
• Cyclonic rain is common in Ireland, especially during the winter months, as fronts move in from the Atlantic
• Relief rain


  1. Air passes over a warm ocean current and picks up moisture

  2. The warm, moist air blows inland from the sea, and it is forced to rise

  3. As the air rises, it cools and condenses into cloud

  4. Rain eventually falls on the mountain's windward side (facing the wind)

  5. The air then sinks down the leeward (sheltered) side of the mountain
• Relief rain is common in mountainous areas off the west coast of Ireland, such as Donegal and Kerry
• Convectional rain


  1. The sun heats the Earth's surface. Air over the land is warmed and expands

  2. As the air expands, it rises rapidly. The air rises, cools and condenses into droplets

  3. This causes cumulus cloud to form

  4. Convection rainfall often occurs as heavy, thundery showers
• Convectional rainfall is common in areas near the equator. It occurs in Ireland during hot, sunny weather conditions
• Frontal (cyclonic) rain


  1. Cold and warm air masses meet at a front. The light, warm air mass rises up over the heavy, cold air mass

  2. As the warm air rises, it cools and condenses into droplets. This causes stratus cloud to form

  3. Eventually, rain falls. Rain is light at first but becomes heavier
• Cyclonic rain is common in Ireland, especially during the winter months, as fronts move in from the Atlantic
• Relief rain


  1. Air passes over a warm ocean current and picks up moisture

  2. The warm, moist air blows inland from the sea, and it is forced to rise

  3. As the air rises, it cools and condenses into cloud

  4. Rain eventually falls on the mountain's windward side (facing the wind)

  5. The air then sinks down the leeward (sheltered) side of the mountain
• Relief rain is common in mountainous areas off the west coast of Ireland, such as Donegal and Kerry
• Convectional rain


  1. The sun heats the Earth's surface. Air over the land is warmed and expands

  2. As the air expands, it rises rapidly. The air rises, cools and condenses into droplets

  3. This causes cumulus cloud to form

  4. Convection rainfall often occurs as heavy, thundery showers
• Convectional rainfall is common in areas near the equator. It occurs in Ireland during hot, sunny weather conditions
• Frontal (cyclonic) rain


  1. Cold and warm air masses meet at a front. The light, warm air mass rises up over the heavy, cold air mass

  2. As the warm air rises, it cools and condenses into droplets. This causes stratus cloud to form

  3. Eventually, rain falls. Rain is light at first but becomes heavier
• Cyclonic rain is common in Ireland, especially during the winter months, as fronts move in from the Atlantic
• Solar energy heats water near the equator

  1. Water expands and moves north and south

  2. Water is cooler nearer the poles, so is heavier

  3. Difference in temperature forms ocean currents

  4. Water flows from low latitudes to high latitudes

  5. Water reaches high-latitude area, cools and sinks

  6. Creates convection currents in the oceans
• Ocean currents move heat

  From low latitudes to high latitudes
• Warm ocean currents


  Heat the air above them
• Cold ocean currents


  Cool the air above them