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DPT & Relative Humidity Charts Handy Dandy Earth Science Reference Tables Page 747.

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Presentation on theme: "DPT & Relative Humidity Charts Handy Dandy Earth Science Reference Tables Page 747."— Presentation transcript:

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2 DPT & Relative Humidity Charts Handy Dandy Earth Science Reference Tables Page 747

3 : The ratio of the air’s actual water content to its potential water vapor content at a given temperature. Relative Humidity Basically, relative humidity tells you how saturated the air is with water. Relative Humidity = Weight of Potential Water Vapor in Air at Saturation Weight of Water Vapor in Air

4 A psychrometer is used to measure relative humidity. The dry bulb measures the air temperature The wet bulb gives a measure of how unsaturated the air is—the evaporation of water from the wet bulb lowers the temperature reading (and the evaporation depends on the saturation of the air)

5 Dewpoint Temperature: The temperature the air would have to be cooled to saturate the air (causes water to condense

6 The “Dry Bulb” Don’t let it fool you. It is just a thermometer. Don’t let it fool you. It is just a thermometer. It measures the air temperature. It measures the air temperature. Duh! Duh! 20°C

7 The “Wet Bulb” Has a little wet booty tied to the bottom. Has a little wet booty tied to the bottom. Gets cool when water evaporates. Gets cool when water evaporates. 12°C Wet Booty

8 A Dry Day… A lot of moisture will evaporate. A lot of moisture will evaporate. The wet bulb will be a lot cooler than the dry bulb. The wet bulb will be a lot cooler than the dry bulb. 8°C 20°C Difference between wet bulb & dry bulb is 12 °C. 20°C14°C 12°C

9 A Humid Day… A little bit of moisture will evaporate. A little bit of moisture will evaporate. The wet bulb will not be much cooler than the dry bulb. The wet bulb will not be much cooler than the dry bulb. 14°C 20°C Difference between wet bulb & dry bulb is 6 °C.

10 Page 747 & 750 of your Handy Dandy Earth Science Reference Tables Warning #1: Be sure to READ the correct chart: DPT or RH Warning #1: Be sure to READ the correct chart: DPT or RH Warning #2: Dew Point Temperature IS NOT “Difference between wet bulb and dry bulb”. Warning #2: Dew Point Temperature IS NOT “Difference between wet bulb and dry bulb”. Warning #3: The wet bulb temp IS NOT the DPT. Warning #3: The wet bulb temp IS NOT the DPT.

11 Dry-bulb temperature is your air temperature. 20 °C

12 14 °C

13 4 °C

14 Subtract (the difference) between the dry bulb and wet bulb

15 14°C 20°C 20-14=6

16 16°C 18°C 18-16=2

17 8°C 20°C 20-8=12 Put it all together Relative Humidity = 11%

18 10°C 14°C 14-10=4 Relative Humidity = 60%

19 10°C 14°C 14-10=4 Dew Point = 6°C The Dew Point Chart works the same way

20 Try These. Dry Bulb Wet Bulb R Humidity DPT 26°C 20 °C 6 °C 5 °C 12 °C 8 °C 18 °C 17 °C 14 °C 0 °C -3 °C 58% °C 17 °C 86% °C 4 °C 57% °C 4 °C 91% °C 16 °C 100% °C 14 °C 45% °C -9 °C

21 More Difficult. Dry Bulb Wet Bulb R Humidity DPT 21°C19°C 11°C 6 °C 17 °C 17°C 2°C -3 °C 9°C 6.5 °C 70°F 60 °F 82% °C 18 °C 45.5% °C -.5 °C 100% °C 17 °C 20% °C -17 °C 69% °C 3.5 °C 52% °C (50 °F) 11 °C (50 °F) °C 21 °C °C 15 °C

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