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? 57%

Summary 12oC 36% Dry Bulb: 20oC Difference Between: 8 Wet Bulb: ______ Relative Humidity: ________ 12oC 36%

Dry Bulb: 13oC Wet Bulb: 10oC Relative Humidity_____ Dewpoint Temp 68% 7 or 8oC

Dry Bulb: 17oC Relative Humidity: 63oC Wet Bulb: _______ Dewpoint Temp

Exit Card What is the dewpoint temperature if the dry bulb 21oC and the wet bulb is 18oC? What is the relative humidity if the dry bulb is 9oC and the wet bulb is 7oC?