A lesson on 5 different instruments used to gather WX data.

1. Weather Instruments
Anemometers, Barometers, Sling Psychrometers,
Thermometers, and Weather Charts.

2. Air Temp and Thermometer
• “Thermo” = Heat
– Measures the amount of heat
energy in the atmosphere.
– Heat comes from solar radiation
that was absorbed by the
atmosphere and hydrosphere and
goes into the air.
– Measured by THERMOMETER

3. Can you
read this
thermometer?

4. Humidity and Sling Psychrometer
• “Psychro” = Cold
– Measures the amount of water vapor in the air.
– Relative humidity is the current amount of water
vapor in the air compared to the total amount of
water vapor the air can hold.
• When the air is nearly completely filled with vapor, it
feels “muggy” if the air is hot. What word would you
use to describe humidity?
– Measured by PSYCHROMETER

5. Comparing Humidity Levels

6. Can you tell the relative humidity?
• If the
relative
humidity
of the air
is 68%...
How
would it
feel
outside?

7. Wind Speed and Anemometer
• “Anemo” = Wind
– Measures the wind speed in the air.
– Changes in air temperature, air pressure, and
humidity cause air to move (called wind)
– Horizontal (side to side) movement of air: WIND
– Vertical (up and down) movement of air: AIR
CURRENT
– Measured by ANEMOMETER

8. Anemometer… Close Up!

9. Convection Currents or Cells
• Wind is caused by…
– Warm air rises because it is less dense, cooler
sinks because it is more dense.
– This pattern
is called a
convection cell

10. Air Pressure and Barometer
• “Baro” = Weight
– The amount of force exerted by the air’s gas
molecules hitting a surface area.
– Measured in millibars (mb)
– When air heats up, the molecules spread apart
and the air pressure goes down.
– Measured by BAROMETER

11. Reading a Barometer
• Can you read
this
Barometer?
• Standard air
pressure is
29.9 mb of
mercury…
does this
barometer
read at
standard air
pressure?

12. Weather Charts
• Weather Charts have lots of symbols and
information.

13. Fronts and Symbols
• Warm air mass behind a cold air mass
– warm front
• Cold air mass behind a warm air mass
– cold front
• Occluded fronts can signal weakening of
storm
• Stationary fronts prolong bad weather

15. Pressure Systems
• High pressure: typically fair weather 
• Low pressure: typically cloudy, unstable
conditions… Bad weather 
• General movement: west to east in the US

16. Can you read this map?

17. Map Questions…
• What is located where the rain is happening High or Low pressure?
• What do you notice the weather conditions
are like near the H’s?
• What type of front is located in the central
United States?
• What can you predict about future weather
conditions in Arkansas based on this map?

18. Video – “Weather instruments”