What is Relative Humidity? • What is Dew point? • What is the Wetbulb Temperature?
Answers What is Relative Humidity? According to our Glossary, “Relative Humidity is the ratio of the existing amount of water vapor in the air at a given temperature to the maximum amount that could exist at that temperature. It is usually expressed in Percent.” The problem with Relative Humidity is that it changes with the temperature so it’s hard to compare versus time. In other words, assuming the temperature is cold at night and hot during the day, the humidity will always be higher at night and lower during the day. The measurement that meterologists prefer is called Dew point. See below. What is the Dew point? According to our Glossary, the dew point is “the temperature to which a sample of air must be cooled, while the mixing ratio and barometric pressure remain constant, in order to attain saturation by water vapor. When this temperature is below O°C, it is sometimes called the frost point.” In simpler terms, it is a measure of how moist the air is.
