2 Weight of Water Vapor in Air Relative Humidity = : The ratio of the air’s actual water content to its potential water vapor content at a given temperature.Relative HumidityWeight of Water Vapor in AirRelative Humidity =Weight of Potential Water Vapor in Air at SaturationBasically, relative humidity tells you how saturated the air is with water.
3 A psychrometer is used to measure relative humidity. The dry bulb measures the air temperatureThe wet bulb gives a measure of how unsaturated the air is—the evaporation of water from the wet bulb lowers the temperature reading (and the evaporation depends on the saturation of the air)
4 Dewpoint Temperature: The temperature the air would have to be cooled to saturate the air (causes water to condense
5 The “Dry Bulb” Don’t let it fool you. It is just a thermometer. It measures the air temperature.Duh!20°C
6 The “Wet Bulb” Has a little wet booty tied to the bottom. Gets cool when water evaporates.12°CWet Booty
7 A Dry Day… A lot of moisture will evaporate. The wet bulb will be a lot cooler than the dry bulb.20°C20°C14°C12°C8°CDifference between wet bulb & dry bulb is 12 °C.
8 A Humid Day… A little bit of moisture will evaporate. The wet bulb will not be much cooler than the dry bulb.20°C14°CDifference between wet bulb & dry bulb is 6 °C.
9 Page 747 & 750 of your Handy Dandy Earth Science Reference Tables Warning #1: Be sure to READ the correct chart: DPT or RHWarning #2: Dew Point Temperature IS NOT “Difference between wet bulb and dry bulb”.Warning #3: The wet bulb temp IS NOT the DPT.
10 Dry-bulb temperature is your air temperature. 20 °C