Relative Humidity
Relative humidity (RH) is the moisture
content (as water vapor) of the
atmosphere, expressed as a percentage
of the amount of moisture that can be
retained by the atmosphere (moisture
holding capacity) at a given temperature
and pressure without condensation. The
moisture holding capacity of air
increases with temperature. Water loss
is directly proportional to the vapor
pressure difference (VPD) between the
commodity and its environment. VPD is
inversely related to RH of the air
surrounding the commodity.