humidity is the amount of water vapour held in a given volume of air at a given time. Atmospheric water vapour is as a result of evaporation and transpiration.
The humidity of a place can be described as follows:
Absolute humidity
It is the actual amount of water vapour held by a given volume of air at a given temperature and time. Absolute humidity varies according to temperature and pressure.
When air temperature reduces, water vapour condenses consequently lowering the humidity and when the temperature rises, the air is capable of holding more water vapour leading to high humidity
Relative humidity
It is the actual amount of water vapour held by a given volume of air at a given temperature expressed as a percentage ratio of water vapour it is capable of holding
OR It is the ratio of the actual amount of water vapour present in a given volume of air at a particular temperature to the amount of water vapour that the air can hold.
the formula for relative humidity
Relative humidity = (Actual amount of water vapour in a given volume of air/Saturated water vapour content) x 100
Example:
If saturated air at 40o c contains 40g/m3 of water vapour per 1m3 , at a time of measurement the volume of air contains 20g/m3
. Calculate the relative humidity.
Relative humidity = (Actual amount of water vapour in a given volume of air/Saturated water vapour content) x 100
= (20/40) x 100
Relative humidity = 50%
