[CF-metadata] various new standard names

[Christiane Textor]

Dear Jonathan,

Here is my comment on humidity, sorry for the delay.

I guess it should be humidity_ratio rather than humidity_mixing_ratio?
This would solve the problem.

Cheers (a happy new year!),
Christiane

>>  > By analogy with humidity_mixing_ratio, noting that a mass mixing
>> ratio > is not quite the same thing as a mass concentration:
>>  > mass_mixing_ratio_of_ozone_in_air (1)
>>
>> Yes, but "mass_fraction_of_ozone_in_air" exists and this is the same as 
>> mass_mixing_ratio
> 
> It's not the same for water. Specific humidity is the ratio of mass of water to
> mass of moist air, while humidity mixing ratio is the ratio of mass of water to
> mass of dry air. I have been told in the past that the same distinction was
> being made for other atmospheric constituents in our radiation scheme, but 
> looking at web definitions I agree with you that for other consituents MMR is
> identical with mass fraction. Now I am puzzled which we actually use (of course
> there is hardly any difference numerically) so I will check.