4 Elements of Weather

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4 Elements of Weather

• Essential question
• What causes the weather?

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Weather

• Weather is the condition of the air around us at
  a specific place and time.

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WHAT is Weather

• Wind
• Humidity
• Air Pressure
• Temperature

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Wind

• Wind is simply air in motion.
• It is caused by the uneven heating of the earths
  surface by the sun.
• Since the earths surface is made of very
  different types of land and water, it absorbs the
  suns heat at different rates.
• Cooler air rushes under warmer air and creates
  wind.

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Wind
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Measuring Wind

• Wind speed is measured with an anemometer.
• Wind direction is measured by a weather vane or
  wind vane.
• The arrow points to the direction the wind is
  coming from.
• Wind speed uses the Beaufort Wind Scale.

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Wind
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Humidity

• Humidity is the amount of water vapor in the air.
• Warm and hot air can hold more water vapor.
• Cold air does not hold as much water vapor.
• Measured by a hygrometer.

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Air Pressure

• Air pressure is the force of air pushing on an
  area.
• As you go higher in the air, there is less air
  pushing down.

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Air Pressure

• As air is heated, the molecules in the air move
  faster and further apart.
• As air cools, the molecules move slower and are
  closer together.

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Cold Air and Warm Air

• Cold air has higher pressure than warm air
  because the molecules are closer together or more
  dense.
• Because cold air is more dense than warm air, it
  sinks, while warm/hot air rises.

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Measuring Air Pressure

• Air pressure is measured with a barometer.

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Air Pressure

• Differences in air pressure are shown on a
  weather map with circular lines called isobars.
• High pressure areas generally have dry, good
  weather.
• Low pressure areas generally have wet weather.

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Air Pressure Symbols

• A blue H is the symbol for high pressure areas
  on a weather map. This means dry, good weather.
• H Happy weather
• A red L is the symbol for low pressure areas on a
  weather map. This means wet weather.
• L Lousy weather

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Air temperature

• As the suns energy heats up Earths surface, the
  air particles move further apart.
• Earth absorbs heat energy during the day and
  loses heat energy at night.
• Measured with a thermometer.

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Weather

• WHAT is Weather!
• Wind
• Humidity
• Air Pressure
• Temperature
• The condition of the air around us.