The relative humidity is a RATIO of the actual amount of water in the air compared to how much it COULD hold.

How much moisture is in the air relative to how much it can hold

Relative Humidity

The dew point is the temperature that air needs to be cooled to in order to be saturated (completely full of water).

DEW POINT

Dew Point is the temperature it needs to be for air to be completely full of water

Not Doo

Doo

This dew

Dew Point and Relative Humidity

• The instrument used to measure dew points and relative humidity is a sling psychrometer.

1.

Dry Bulb (Air)Temperature

Wet BulbTemperature

DifferenceDewpoint

TemperatureRelativeHumidity

_______ °C _______ °C _______ °C _______ °C _______ %

26°C 18°C

26°C - 18°C =

8

Dry bulb was 26°C

13° C

26°C

1.

Dry Bulb (Air)Temperature

Wet BulbTemperature

DifferenceDewpoint

TemperatureRelativeHumidity

_______ °C _______ °C _______ °C _______ °C _______ %

26°C 18°C

25°C - 18°C =

8

Dry bulb was 26°C

13° C

45%

1.

Dry Bulb (Air)Temperature

Wet BulbTemperature

DifferenceDewpoint

TemperatureRelativeHumidity

_______ °C _______ °C _______ °C _______ °C _______ %

26°C 18°C

26°C - 18°C =

10

Dry bulb was 26°C

45%13° C

5 48% 1°C

5°C

2°C

1°C

48% 1°C

83%

86%

19°C

4°C

20°C

20°C 91.5%

14°C

996

0.25

32

30

35/ 5

903

32

30

25\ 2

903

10\ 70

65

1

Link to Smart Board

1. The lowest air temperature occurred at what time?

2. The highest relative humidity reading occurred at what time?

3. The highest air temperature occurred at about what time?

4. The lowest relative humidity occurred at about what time?

6 am6 am

6 am6 am

3 pm3 pm

3 pm3 pm

5. According to the graph, what happens to the relative humidity as the air temperature increases?

6. At what time(s) did the air temperature equal the dew point?

7. What was the relative humidity (%) when the air temperature equaled the dew point?

As Temperature Increases- Relative Humidity DecreasesAs Temperature Increases- Relative Humidity Decreases

6 am6 am

100%100%

8. Condensation (water coming out of the air) is most likely to occur at approximately what time?

9. At approximately what time was the rate of evaporation highest?

10. The greatest change in air temperature occurred during the period from:

A) midnight to 6AM B) noon to 6PM

C) 6AM to noon D) 6PM to midnight

6 am6 am

3 pm3 pm