Hi Stuart, Yes, you cannot change VMR if you do this. It is true you can also decide to divide by 0.20946 instead of vmr[I] to allow this change. This would be more inline with what is done today, so still not in line with what is done in the original model.
About the other models, I copied this from one of them so the issues should be the same there as here. I don’t have any strong opinion on these and how it should change. Others will have to comment if they want to keep the current faulty version or not. I think the newest one should change. With hope, //Richard > On 22. Oct 2021, at 12:52, Fox, Stuart <stuart....@metoffice.gov.uk> wrote: > > Hi Richard, > > I’m not sure about your proposed change to line 13421. As I understand it, if > you do this then you will calculate the same absorption for oxygen regardless > of what the user inputs for the O2 vmr. Is this desired behaviour? The > MPM-type coefficients and equations in the Tretyakov 2005 paper assume a > particular vmr (0.20946). Is it more correct to divide the calculated > absorption by this value, and then multiply by the user-supplied vmr at the > stage of the absorption calculation? > > I also notice that the same VMRISO is in lots of the other complete O2 models > (MPM87, MPM89 etc), so this isn’t restricted to Tretyakov-05 > > Stuart > > From: Richard Larsson <ric.lars...@gmail.com> > Sent: 22 October 2021 10:45 > To: Fox, Stuart <stuart....@metoffice.gov.uk> > Cc: arts_dev.mi@lists.uni-hamburg.de > Subject: Re: Another Tretyakov-05 O2 absorption question > > This email was received from an external source. Always check sender > details, links & attachments. > > Hi Stuart, > > I think you have found a bug. The isotopologue ratio is not fixed anywhere, > yet the VMRISO variable has been scaled down by its assumed value. The > comment for this value is simply false today, it must have changed sometime > without anyone noticing. > > I think that VMRISO should be changed to simply be equal to the input vmr > value. > > The particular line for the VMRISO number today is legacy_continua.cc::13327. > If that line is commented out and instead line legacy_continua.cc::13421 is > rewritten as "(...) / vmr[i]", I think you will get better results. > > Could you check if this change improves your results? > > With hope, > //Richard > > Den mån 18 okt. 2021 kl 12:28 skrev Fox, Stuart <stuart....@metoffice.gov.uk>: > Hi ARTS devs, > > I’ve got another question about the Tretyakov-05 complete absorption > implementation in ARTS. In the code for TRE05O2AbsModel, the line absorption > is calculated, and then converted in the final line into a partial > cross-section. When calculating this cross-section a constant equal to the O2 > vmr assumed by Tretyakov 2005 (0.20946) multiplied by the main isotope > abundance is used, rather than just the O2 vmr. Should the isotope abundance > really be included here? Presumably it depends on whether it is also included > at the stage of the absorption calculation, or if the total O2 vmr is used > there, but I’m not familiar enough with the ARTS code to know which is the > case? I guess I would expect it should work properly for the case where the > user defines “abs_species_O2” without explicitly setting an isotopologue > ratio; the tests I’ve done suggest this is not currently the case. > > Regards, > > Stuart
