Understanding Humidity in the Crabitat

Originally written by Vanessa Pike-Russell-Updated by Stacy Griffith

What is Humidity?

Humidity is a measure of the amount of water vapor in the air. It can be expressed in several ways.

“Specific humidity” is the mass of water vapor per unit mass of combined dry air and water vapor, generally expressed in grams per kilogram. The specific humidity of an air parcel does not change with temperature.

“Absolute humidity” is the density of water vapor, expressed as grams per cubic meter of air.

“Relative humidity” is discussed below. Related terms are “saturation,” which describes the condition where water vapor is at a maximum concentration for the air temperature (warm air can hold more moisture than cold);

“dew point temperature” the temperature at which saturation occurs if air is cooled at constant pressure without addition or removal of water vapor; and

“vapor pressure,” which in meteorology is that part of the total atmospheric pressure due to water vapor content.

Reference: Arctic Climatography and Meteorology