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http://www.chm.davidson.edu/ronutt/che115/Phase/Phase.htm
Figure 2. The mean distribution of precipitable water, or total atmospheric water vapor above the Earth's surface, for 1992. This depiction includes data from both satellite and radiosondeobservations. (Image courtesy of Thomas Vonder Haar and David Randel, Colorado State University, Fort Collins.)
Humidity
Normal sea level pressure is around 1000 mb
Vapor Pressure in mb is the fraction of the total air pressure coming from the molecular movement of water vapor molecules.
So 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 vapor
A saturation humidity of 10 mb means that at most 1 % of all air molecules Can be water vapor
Humidity
Absolute humidity = Mass of water vapor volume of air
Specific humidity = Mass of water vapor total mass of air
Mixing ratio = Mass of water vapor mass of dry air
Other measures that are used.
g/m3
g/kg
g/kg
Saturation Vapor Pressure vs Temperature
500
600
700
800
900
1000
80 90 100 110
Temperature (°C)
Mt. Hood
Mt. Rainer
Relative Humidity
RH Actual _ Humidity
Saturation _Humidity
Saturation Vapor Pressure (mb) vs Temp. C
0
5
10
15
20
25
30
35
40
-10 0 10 20 30
Temperature (°C)
A
B
Dew point Temperature(directly linked to actual humidity)
Temperature that results in saturation or dew forming on surfaces.
High dew point high actual humidityLow dew point low actual humidity
Dew points in excess of 70 F will normally make one uncomfortable.
Outside
T = -15 CTd = -15 CRH =100%
Inside
T = 20 CTd = -15 CRH = 8%
Hygrometers measure humidity
A Sling Psychrometer is common
