4 Fill in this chart Air temperature in CWater vapor density in g waterKg air

# 4 fill in this chart air temperature in cwater vapor

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4) Fill in this chart: Air temperature in ° C Water vapor density in g water/Kg air Dew point temperature in ° C 4a 30 10 15 4b 30 20 25 4c 40 10 15
You can find relative humidity from dew point. Example The air temperature is 50° C and the dew point temperature is 40° C°. What is the relative humidity? We need to realize that one of the important numbers that we need to get off of the graph is the current amount of moisture in the air. The dew point temperature is important for determining this. Let’s look at the graph below. The red curve shows the saturation points (100% relative humidity). The dew point temperature is when the air is saturated. If you take saturated air and warm up, this doesn’t change the amount of moisture in the air. Our 50 ° C air would become saturated when cooled to 40 ° C, and become unsaturated if it warmed to 50 ° C again, the whole time having the same amount of moisture in the air. We use our dew point temperature, then, knowing that we can read the amount of moisture in the air off the graph because the graph shows saturation values for moisture content. Looking at the graph below, go to 40 ° C and go straight up to find that the moisture level in the air is 50 g of water per
Kg of air. If the air is warmed to 50 ° C (see block arrow below), which is our actual temperature, the air still has 50 g of water per Kg of air. At 50° C, the maximum moisture level is about 95 g of water per Kg of air (at saturation, see other block arrow), so the relative humidity is 50 g of water per Kg of air/95 g of water per Kg of air x 100% = 53% You can also find the dew point temperature from the relative humidity working the problem in reverse. Example If is currently 30 ° C out and the relative humidity is 75%. What is the dew point temperature? At 30 ° C, the air holds a maximum of about 28 g of water per Kg of air (reading the graph above). 75% of this is .75 x 28 = 21. Therefore, the actual moisture content is 21 g of water per Kg of air. At 30 ° C on the above graph, go up to 21 g of water per Kg of air (see skinny arrow draw in) and read across to where
the arrow meets the red curve indicating saturation. It looks like the air would have to cool to about 26 ° C to be saturated. Therefore, the dew point temperature is 26 ° C. 5) Fill out the following table: Actual air temperature dew point temperature Actual moisture content in air in g of water per Kg of air (water vapor density) Moisture content in air at actual air temperature in g of water per Kg of air (water vapor density) if the air was actually saturated Relative humidity in % 5a 42 ° C 37 40 55 72.7% 5b 37° C 10° C 8 42 19% 5c 48° C 38 48 80 60 5d 31 18° C 15 30 45 5f 42 20° C 16 50 25 5g 53 26 20 30 66.7%

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• Spring '17
• John DOe
• Meteorology, Atmospheric thermodynamics, Water vapor, Psychrometrics, g/kg

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