METEOROLOGIST JEFF HABY
Riddle: The temperature is 110 F in Las Vegas. What does the
dewpoint need to be in order for the
relative humidity to be 5%?
Answer to Riddle: The
relative humidity has the formula of RH = (e/es)*100%
110 F = 43.33 C
es can be found by using the
Classius-Clapeyron equation
LN(es/6.11) = 5321.0415*(1/273 - 1/T)
T = 43.33 C = 316.33 K
es = 6.11*e^(5,321.041215*(1/273 - 1/316.33)
es = 88.21 mb
Next, solve of e using RH equation
5 = 100e/88.21
e = (5*88.21)/100 = 4.4105 mb
Next, use Classius-Clapeyron equation to solve for dewpoint
LN(e/6.11) = 5,321.041215*(1/273 - 1/Td)
LN(4.4105/6.11) = 5,321.041215*(1/273 - 1/Td)
-0.325938711 = 5,321.041215*(1/273 - 1/Td)
-0.325938711 / 5,321.041215 = (1/273 - 1/Td)
-0.000061255 = (1/273 - 1/Td)
-0.000061255 - 1/273 = -1/Td
-0.003724258 = -1/Td
0.003724258 = 1/Td
Td = 1/0.003724258
Td = 268.5 K = -4.5 C = 24 F
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