Specific Humidity or Humidity Ratio:
Specific or absolute humidity or humidity ratio or moisture content is described as the ratio of the mass of water vapour along with the mass of dry air in a given volume of the combination. It is mention by the symbol ω.
...6.10
here the subscripts a & v refer to dry air & water vapour respectively. Now
![1576_Specific Humidity or Humidity Ratio1.png](https://www.expertsmind.com/CMSImages/1576_Specific%20Humidity%20or%20Humidity%20Ratio1.png)
Putting for mv and ma from these expressions in Eq. ( 6.10) ,we get the following
...6.11
The unit of ω is kg of water vapour per kg of dry air. Also, as p mention the actual total atmospheric pressure, then from Dalton's law
p = pa + pv ...6.12
So that
...6.13
Referring that the total atmospheric pressure is constant at a specific locality, we can see that
ω = f (pv)
viz., the specific humidity is only a function of the partial pressure of water vapour.