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RELATIVE HUMIDITY RIDDLE

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