Relative Humidity

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Relative Humidity
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Hot Air

• Warm air has more energy and more space between
  each molecule.
• It can hold more water vapor than colder air
• More Water

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Cold Air

• Cold air has less energy and the molecules are
  closer together.
• It cant contain as much water vapor as warmer
  air can.
• Less Water

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It Depends

• Relative humidity is how much water vapor is in
  the air compared to how much there could be if
  the air was saturated or full.

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Hot vs Cold

• A relative humidity of 50 on a hot day would
  mean there was more water vapor in the air than
  50 relative humidity on a cold day.
• It would be wetter

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Dropping Temperature

• So, if the amount of water vapor stays the same
  but the temperature goes down, the relative
  humidity would go up

Humidity
Temperature
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Rising Temperature

• If the amount of water vapor stays the same and
  the temperature goes up, the relative humidity
  will go down.

Humidity
Temperature
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The most water in the air

• Even on the hottest day, with very high relative
  humidity, the percent of the air that is water
  vapor is never more than about 4.

4
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Measuring Humidity

• You can measure the relative humidity by figuring
  out how much water can evaporate into the air
  around you at a given temperature.
• The difference in temperature between a dry
  thermometer and a wet thermometer can be used to
  calculate the humidity.

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• If the air already has a lot of water vapor in
  it, not much new water can evaporate.
• If the air is dry lots of water can evaporate.
• It takes heat from the air to help water
• evaporate making the
• temperature of the
• thermometer go
• down.

temperature