Humidity 1

The amount of water vapor in the air can be specified in two ways.

1. specify as the mass of water vapor (mv) present in a unit mass of dry air (mda).
   This is called “absolute” or “specific” humidity or also called as humidity ratio –> w

w = mv/mda —> kg water vapor / kg dry air

2. specified as the amount of moisture the air holds (mv) relative to the maximum amount of moisture the air can hold at the same temperature (mv_max).
   The ratio of these two quantities is called the relative humidity (rh).

rh = mv/mv_max —–> unitless ( or %)

The relative humidity ranges from 0 for dry air to 1 (100%) for saturated air.