Review Books
•Pages 316-317
#s 1, 2, 3, 4, and 6
Aim: How can we measure
relative humidity?
Topic: Unit 6 Meteorology
Main Idea: Measuring Relative Humidity
1) What is a sling psychrometer?
• It is an instrument with two thermometers used
to measure relative humidity and dewpoint.
Dry Bulb
• Measures air temperature
• Is always the higher temperature
• Measured in degrees Celsius
Wet Bulb
• The thermometer with
the cloth
• Evaporation occurs,
this is a cooling process
• Never higher than dry
bulb
• Measured in degrees
Celsius
3) What do the two temperatures tell
you about the air?
• Close temperatures= high humidity
• Far apart temperatures= low humidity
How do we use the charts on page 12 of the
earth science reference tables?
• Step 1: Find the dry bulb
temp. on the left side
• Step 2: Subtract the wet bulb
from the dry bulb
• Step 3: Find the difference
across the top of the chart
• Step 4: See where the
column and row meet
• What is the relative humidity if the dry bulb is
12oC and the wet bulb is 8oC?
Summary
Dry Bulb: 20oC Difference Between: 8
Wet Bulb: ______ Relative Humidity: ________
Dry Bulb: 13oC Wet Bulb: 10oC
Relative Humidity_____ Dewpoint Temp. ______
Dry Bulb: 17oC Relative Humidity: 63%
Wet Bulb: _______ Dewpoint Temp. _______
Exit Card
1) What is the dewpoint temperature
if the dry bulb 21oC and the wet
bulb is 18oC?
2) What is the relative humidity if the
dry bulb is 9oC and the wet bulb is
7oC?