RE: Abd's comment about, "the instrument does not provide mass of water as vapor, unfortunately, that's not what it shows. It reads in g/m^3. To convert this to mass we'd need to know the volume, eh?"
NO, you do NOT need to know the volume to calculate the mixing ratio if you have measurements of the proper other variables. In atmospheric science the mixing ratio is a very common and key variable. It is always CALCULATED from other more common variables which do NOT include flow rate or volume. This is gas law and in gas law, concentrations do not matter... Its all about mass or Mole fraction. I will provide the explanation shortly, but I have to run an errand... I may not get to it this eve, but I will definitely respond. -Mark
