Three primary measurements of humidity are widely employed: absolute, relative  and specific. Absolute humidity describes the water content of air and is expressed in either grams per cubic metre or grams per kilogram  .Perry, R.H. and Green, D.W, (2007) Perry's Chemical Engineers' Handbook (8th Edition), Section 12, Psychrometry, Evaporative Cooling and Solids Drying McGraw-Hill, Relative humidity,  expressed as a percentage, indicates a present state of absolute humidity relative to a maximum humidity given the same temperature. Specific humidity is the ratio of water vapor mass to total moist air parcel mass.
Three primary measurements of humidity are widely employed: absolute, relative , and specific. Absolute humidity is expressed as either mass of water vapor per volume of moist air (in grams per cubic metre ) or as mass of water vapor per mass of dry air (usually in grams per kilogram ) .Perry, R.H. and Green, D.W, (2007) Perry's Chemical Engineers' Handbook (8th Edition), Section 12, Psychrometry, Evaporative Cooling and Solids Drying McGraw-Hill, Relative humidity, often expressed as a percentage, indicates a present state of absolute humidity relative to a maximum humidity given the same temperature. Specific humidity is the ratio of water vapor mass to total moist air parcel mass.
A
,
R
describes the water content of air and is expressed in either
is expressed as either mass of water vapor per volume of moist air (in
R
or
) or as mass of water vapor per mass of dry air (usually in
A
)
A
often