Dew point is defined as the temperature at which dew will form. When the dew point equals the temperature, the relative humudity is 100%. Whenever the relative humidity is less than 100% the dew point is always less than the air temperature.
Let's calculate a dew point using the equation above.
The air temperature is 20° Celsius and the relative humidity is 50%.
What is the dew point?
First, we'll solve for 'n'.
n = [ln (50 ÷ 100) + (17.27 • 20) ÷ (237.3 + 20)] ÷ 17.27
n = [ln (.5) + 345.4 ÷ 257.3] ÷ 17.27
n = [ -.69314718056 + 1.3424018655] ÷ 17.27
n = 0.6492546849 ÷ 17.27
n = 0.0375943651
Now we put the value of 'n' into the second equation:
d = (237.3 • 0.0375943651) ÷ (1 -0.0375943651)
d = 8.9211428382 ÷ 0.9624056349
dewpoint = 9.2696286417 Celsius
dewpoint = 9.27 Celsius (rounded)
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