Weather Measurement Tools. Thermometer What? –Measures the air temperature Measurement unit: degrees Celsius (°C) (in Canada) or (°F) in some other areas.
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Presentation on theme: "Weather Measurement Tools. Thermometer What? –Measures the air temperature Measurement unit: degrees Celsius (°C) (in Canada) or (°F) in some other areas."— Presentation transcript:
Thermometer What? –Measures the air temperature Measurement unit: degrees Celsius (°C) (in Canada) or (°F) in some other areas of the world
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”.
Mercury ThermometersAlcohol Thermometers No longer used in schools – hazard to health! Commonly used in schools and hospitals now!
Psychrometer What? –Measures humidity (water level) in the air – relative humidity Measurement Unit: percent (%)
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.
–Low humidity - evaporation occurs more easily –Thus more cooling and a lower temperature on the wet bulb thermometer.
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.
Barometer. What? –Measures atmospheric pressure - if there is low or high pressure Measurement unit: hPa (hectoPascals) or mm http://www.ludolph.de/Handel%20Barometer%20262238.jpeg www.usatoday.com/weather/wbaromtr.htm http://geography.sierra.cc.ca.us/booth/Physical/chp5_atm_pressure/barometer.gif
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.
Did you ever notice that your toilet bowl water level goes down when there is a storm? Why?
Anemometer What? –Measures wind speed Measurement unit: usually kilometers per hour (km/h) http://www.delta-education.com/productdetail.aspx?Collection=N&prodID=2039&menuID=31
How? –By counting the number of revolutions in a set amount of time. (Calibration required)