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Types of Rainfall

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Year 8 lesson describing the different types of rainfall.

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Types of Rainfall

  1. 1. Geography Rainfall TypesRainfall Types Aim : Why does it rain?
  2. 2. Geography Why does it rain?Why does it rain? Try to guess which word fits? The sun heats the earth’s surface and in turn the air above it becomes cool/warmcool/warm and it rises/fallsrises/falls by the process of confusion/convectionconfusion/convection. As it falls/risesfalls/rises, the air warms/coolswarms/cools until the water vapour evaporates/condensesevaporates/condenses, forming thick/thinthick/thin clouds.
  3. 3. Geography • During summer days the earth’s surface can becomes very hot. • This can cause an intense warming of the air making it very buoyant. • The air rises quickly. • As it does so it expands and cools. The air can no longer hold • the moisture; condensation takes place and rain forms. • The cool air then falls and • is caught and dragged back • upward by more rising air • forming a convection cell. Convectional RainConvectional Rain
  4. 4. Geography Frontal RainFrontal Rain • A warm air mass tries to force into a cold air mass. • The warm air is lighter and less dense than the cold air and so is forced to rise over it. • As the warm air rises it expands and cools and so rain forms.
  5. 5. Geography This line represents the front separating warm air from cold air Rain Cumulus cloud Warm air Warm air rises over cold air; it expands and cools, condenses, clouds and rain form Warm air Cool air
  6. 6. Geography Orographic (Relief) RainOrographic (Relief) Rain • Upland areas force the warm moist air upward, where it cools. • As the warm air rises it expands and cools, condensation takes place and rain forms. • The rain is often heavy and prolonged.
  7. 7. Geography Sea Moist wind Rain Dry wind Little or no rain Pressureincreases Pressuredecreases When air rises the pressure on it decreases; the expands and cools When the air descends the pressure on it increases; the air contracts and warms

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