Hi Pauline,

Relative humidity (RH) is not supported in qpack and arts. What 
documentation indicates the opposite?

One reason for not supporting RH, is that this would give a link between 
humidity unit and temperature jacobians. If the state variable for water 
vapour is RH, the temperature jacobians must be adjusted. So a warning 
if you plan to combine RH with temperature retrievals.

If not, you can do a trick that I have used when trying out some RH 
retrievals. Set the a priori profile to match 50% RH. If you use rel, 
and the retrieved value is 2, you have a RH of 100% etc. You can of 
course also use logrel, but then 50% and 100% RH corresponds to 0 and 
log(2), respectively.

And if using RH, an important aspect is how to treat the stratosphere. 
RH works poorly above the tropopause.

Bye,

Patrick



On 06/10/15 10:07, Pauline Martinet wrote:
> Hi everybody,
>
> I am not sure about something.
>
> I am using qpack2 to retrieve humidity profile.
>
> I would like to do the retrieval on log of relative humidity. I can see
> this option in the documentation I just have to
> change Unit from vmr to relative humidity.
>
> However, does it mean the humidity profile provided to ARTS through
> qpack (Q.ABS_SPECIES(2).ATMDATA.DATA field)  should also be given in log
> relative humidity ?
>
> Thank you very much for this information.
>
> Best regards,
>
> Pauline
>
>
> ----- Météo-France -----
> Dr. Pauline Martinet
> Chercheur CNRM/GMEI/LISA
> [email protected]
> Fixe : +33 561079031
> Site web: www.sites.google.com/site/martinetpauline31
> <https://www.sites.google.com/site/martinetpauline31/>
>
>
>
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