Weather Measurement Tools

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Weather Measurement Tools
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Thermometer

• What?
• Measures the air temperature
• Measurement unit degrees Celsius (C) (in
  Canada) or (F) in some other areas of the world

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• How do they work?
• Heat expands the liquid in the vacuum tube and
  causes it to rise
• Cold causes the liquid in the vacuum tube to
  contract or fall.

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• Mercury Thermometers

• Alcohol Thermometers

Commonly used in schools and hospitals now!
No longer used in schools hazard to health!
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Psychrometer

• What?
• Measures humidity (water level) in the air
  relative humidity
• Measurement Unit percent ()

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• How?
• Compare the temperature of a dry bulb
  thermometer with that of a wet bulb
  thermometer.
• When water evaporates from the wet cloth it
  absorbs heat and produces a cooling effect on the
  wet bulb thermometer.

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• Low humidity - evaporation occurs more easily
• Thus more cooling and a lower temperature on the
  wet bulb thermometer.

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• High humidity less evaporation will take place
• Less cooling and not as great of a difference
  between the wet and dry bulb readings.
• The wet bulb thermometer will most always have
  the lower temperature.

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Barometer .

• What?
• Measures atmospheric pressure - if there is low
  or high pressure
• Measurement unit hPa
• (hectoPascals) or mm

www.usatoday.com/weather/wbaromtr.htm
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http//geography.sierra.cc.ca.us/booth/Physical/ch
p5_atm_pressure/barometer.gif
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• How?
• A glass vacuum tube is inserted into a dish of
  mercury.
• The air pressing down on the mercury in the
• dish forces some of the mercury up into the
  glass tube.

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• Did you ever notice that your toilet bowl water
  level goes down when there is a storm?
• Why?

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Anemometer

• What?
• Measures wind speed
• Measurement unit usually kilometers per hour
  (km/h)

http//www.delta-education.com/productdetail.aspx?
CollectionNprodID2039menuID31
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• How?
• By counting the number of revolutions in a set
  amount of time.
• (Calibration required)