6Figure 2. The mean distribution of precipitable water, or total atmospheric water vapor above the Earth's surface, for This depiction includes data from both satellite and radiosondeobservations. (Image courtesy of Thomas Vonder Haar and David Randel, Colorado State University, Fort Collins.)
18HumidityVapor Pressure in mb is the fraction of the total air pressure coming from the molecular movement of water vapor molecules.Normal sea level pressure is around 1000 mbSo a vapor pressure of 10 mb means that 1% of all air is water vapor.20 mb 2%40 mb _______ %An actual humidity of 10 mb means that 1 % of all air molecules are water vaporA saturation humidity of 10 mb means that at most 1 % of all air moleculesCan be water vapor
19Humidity Other measures that are used. Mass of water vapor volume of airAbsolute humidity =g/m3Mass of water vaportotal mass of airSpecific humidity =g/kgMass of water vapormass of dry airMixing ratio =g/kg
26Dew point Temperature (directly linked to actual humidity) Temperature that results in saturation ordew forming on surfaces.High dew point high actual humidityLow dew point low actual humidityDew points in excess of 70 F will normally make one uncomfortable.