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WEATHER . Weather vs. Climate Weather – the atmospheric conditions over a relatively short period of time Climate – the weather in some location averaged over a long period of time. Weather Measurements.

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Weather vs. Climate

Weather – the atmospheric conditions over a relatively short period of time

Climate – the weather in some location averaged over a long period of time

Weather Measurements

What weather phenomena do we need to measure? What instruments do we use to measure them?

Coe Lake Weather MeasurementsTradition & Electronic

  • Temperature

  • Atmospheric Pressure

  • Rainfall

  • Relative Humidity

  • Wind Direction

  • Wind Speed


  • These cloud types should be familiar to you. Write down the website if you need to go back to revisit them.

  • “Cirrus” or “Cirro” – high (base above 6000 m)

  • “Alto” – mid (base 2000 m-6000 m)

  • No prefix – low clouds


  • Two scales – Celsius & Fahrenheit


    • Boiling Point of Water212 °F100 °C

    • Average Body Temperature98.6 °F37 °C

    • Hot Summer Day85 °F29.4 °C

    • Average Room Temperature68 °F20 °C

    • Cool Fall Day55 °F12.8 °C

    • Warm Winter Day40 °F4.4 °C

    • Freezing point of Water32 °F0 °C

      • You must know ABT & ART in °C

      • You must know the BP & FP of Water in °C


  • We use a variety of thermometers at Coe Lake

    • All measurements will be done in Metric!

    • Digital thermometers

    • Thermometers with various scale markings that make it challenging for students to read

    • “What’s Hot & What’s Not?”

    • “Weatherwise”



  • Atmospheric pressure (or air pressure) is the weight of Earth's atmosphere on the surface at a given location and is generated by the downward force of Earth's gravity.

  • Atmospheric pressure depends on the amount of air above the location where the measurement is taken, consequently the pressure drops as you go higher.

  • Also known as Barometric Pressure because it is measured with a barometer.

Barometric Pressure Unit Craziness!

  • National Weather Service:

    • inches of Mercury (inHg)

    • mm of Mercury (mmHg)

    • hectoPascals (hPa)

      • A Pascal is the metric unit for air pressure and 100,920 Pa is equal to 1009.20 hPa

    • millibars (mb) (same as hPa)

Average Atmospheric Pressure at Sea Level

  • In Weatherspeak:

    • 29.9 inHg

    • 1013.25 hPa

    • 1013.25 mb

  • In Chemspeak:

    • 101.325 kPa

    • 760 mmHg

    • 1.00 atm

    • 14.7 psi


Rainfall (Snowfall)

  • Rainfall impacts all of us, from the lack of rain during times of drought to the dangers of flash floods when we receive too much rain too fast.

  • It is the depth of water reaching the ground, typically in inches or millimeters.

  • Rainfall rate

    • Light = 0.10 inches of rain per hour

    • Moderate = 0.10 to 0.30 inches of rain per hour

    • Heavy = over 0.30 inches of rain per hour


  • An inch of rain is exactly that, water that is one inch deep.

  • One inch of rainfall equals 4.7 gallons of water per square yard or 22,650 gallons of water per acre! Wow!

  • Measured with a Rain Gauge.

Rain Gauges

Relative Humidity

  • The amount of moisture in the air relative to how much moisture the air can hold.

  • Temperature dependent.

  • Higher temperatures – the air can hold more moisture. (Think about hot, humid summer days…)

  • Lower temperatures – the air holds less moisture. (The relative humidity might be the same as a hot summer day, but less moisture will be in the air.)

Relative Humidity

  • Humidity is measured with a hygrometer.

  • Relative humidity is measured with a Sling Psychrometer.

  • Humidity measurements can be used to calculate dew point and heat index.

Relative Humidity Chart

Heat Index

Measuring Humidity

Wind Measurement

  • Wind is the natural motion of the air roughly parallel to the Earth's surface.

  • It is caused by the unequal heating and cooling of the Earth and atmosphere by the sun, which produces differences in air pressure.

  • Air tends to flow from areas of higher pressure to lower pressure.

Wind Measurement

Wind occurs at all scales.

  • Global winds (trade winds)

  • Upper level winds (jet streams)

  • Synoptic winds (resulting from the pressure differences of surface air masses)

  • Local (mesoscale) winds (such as gust fronts)

  • Winds that develop because of geographical features (like sea breezes).

  • Winds also occur on a much smaller scale, for example dust devils or tornadoes.

Wind Measurement

Wind measurements are taken at a fixed location and measure two parameters:

  • Wind Speed – mph, kph, knots

  • Wind Direction – cardinal directions; always naming the wind for the direction from which it comes

    • EX: a SE wind comes from the southeast

Wind Speed – Anemometer

Wind Direction – Wind Vane

What do you need to know?

  • What are the various weather phenomena and

    • What are the definitions?

    • What tool is used to measure it?

    • What metric unit is used to measure it?

  • Match the name of the cloud to its altitude using the correct prefixes (alto & cirro)

  • What are the metric and English (F) temperatures for the bp & mp of water, body temperature & room temperature?

  • What is the difference between weather and climate?

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