How to Compare Relative Humidity in Cities

Calculate Relative Humidity & Compare

• 1

  Us the dry bulb thermometer to measure the air temperature, record this number in degrees Celsius.

• 2

  Cover the bulb of the wet thermometer with a small moistened muslin bag. Because the muslin bag has been added, the reading will show a lower temperature than the dry bulb thermometer did. Record the temperature shown in degrees Celsius, this number is the dewpoint.

• 3

  Calculate the saturation vapor pressure in millibars using the formula: Saturation Vapor Pressore = 6.11 x 10.0 x (7.5 x Air Temperature /(237.7+ Air Temperature))

• 4

  Calculate the actual vapor pressure in millibars using the formula: Actual Vapor Pressure = 6.11 x 10.0 x (7.5 x Dewpoint/(237.7+ Dewpoint)).

• 5

  Calculate relative humidity now using the formula: Relative Humidity in percent = (Actual Vapor Pressure/Saturation Vapor Pressure) x 100

• 6

  Repeat these steps for each city you wish to compare the relative humidity of and once complete you can compare the relative humidities side-by-side.