Taylor13, I agree that the statement 'related to the mass fraction of the dry air' is somewhat vague. I admit I was using the definition as given in the instrument manual for the Lufft WS501 weather station that we use in our installations.
I think that your statement is correct above, but I wanted to share one more definition: definition: Specific enthalpy (enthalpy per kg of dry air) of moist air is the sum of the specific enthalpy of dry air and the specific enthalpy of the water vapor in the air. I wonder if we should use 'sum of the enthalpies of dry air and water vapor in the air' instead of 'approximated by a mass-weighted mean'? For completeness, here is the equation for Specific enthalpy: h = ha + H*hg; where ha is the specific enthalpy of dry air, H is the humidity ratio, and hg is the specific enthalpy of water vapor. ha, This is given by the equation cpa*T; where cpa is the specific heat of air, and T is the temperature of air. You have to memorize the value of cpa which is 1.006 kJ/kgC since this is constant. T must be given in the problem, or it can simply be measured with a thermometer or other temperature measuring devices. H, Humidity ratio is the ratio of the mass of water vapor in the moist air and the mass of dry air. In layman's terms, it gives the wetness of air. Along with the temperature of air, this must be given in the problem. Hg. Using a steam table, this can easily be found. Once you have the temperature, bring out your saturated steam table and look for the value of hg. This value has the units kJ/kg. -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/cf-convention/cf-conventions/issues/311#issuecomment-759681990 This list forwards relevant notifications from Github. It is distinct from cf-metad...@cgd.ucar.edu, although if you do nothing, a subscription to the UCAR list will result in a subscription to this list. To unsubscribe from this list only, send a message to cf-metadata-unsubscribe-requ...@listserv.llnl.gov.
