It seems that everyone complains about the dry air found indoors during the winter. When cold air from the outside comes inside through an open door or a poorly sealed window, the furnace heats this air, which reduces the relative humidity of the air to uncomfortable levels. The result is dry skin, chapped lips, and a tickly throat. On today’s episode of Weather Break, Creighton University student Ross Caniglia asks Dr. Jon Schrage why the air is so dry in the winter.
There are many ways to define the relative humidity of the air. In today’s discussion, Dr. Schrage refers to the relative humidity as the ratio of the amount of water vapor the air “is holding” to the amount of water vapor the air “could hold” at the current temperature. This is a pretty informal definition, but it works in this context. Here, the amount of water vapor the air “could hold” depends on temperature in accordance with the Clausius-Clapeyron equation.
Today’s discussion emphasized the INDOOR relative humidity. For maps of the dewpoint (another measure of humidity), see Unisys Weather.