Rainfall Types

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Rainfall Types
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Convectional Rain

• During summer days the earths 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.

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Negative Charge
Cumulonimbus cloud
Positive Charge
Cool air descends and replaces warm air
Lightning
Movement of Storm
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Frontal 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.

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Warm air rises over cold air it expands and
cools, condenses, clouds and rain form
Warm air
This line represents the front separating warm
air from cold air
Cumulus cloud
Rain
Warm air
Cool air
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Orographic (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.

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When the air descends the pressure on it
increases the air contracts and warms
When air rises the pressure on it decreases
the expands and cools
Pressure decreases
Pressure increases
Rain
Dry wind
Moist wind
Little or no rain
Sea