Hi Richard,

I think I have now tracked down the source of my issue (and identified the fix)!

It seems there has been a change to the way that ReadARTSCAT works? Previously 
it looks like it re-initialised the abs_lines variable each time it was called, 
whereas now it appears to append onto the end of the existing variable. Since I 
am reading separate line files for H2O and O3 the way I was approaching this 
Append(abs_lines, temp_lines)
Append(abs_lines, temp_lines)

Using the new behaviour I can either just use two calls to ReadARTSCAT to read 
directly into abs_lines (assuming this is actually the intended behaviour?), or 
reset temp_lines between the two calls. Without this then, as suspected, it 
adds the H2O lines twice.

Does this make sense?


From: Richard Larsson <ric.lars...@gmail.com>
Sent: 17 March 2022 13:13
To: Fox, Stuart <stuart....@metoffice.gov.uk>
Subject: Re: Help, something broke my simulations!

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links & attachments.
Hi Stuart,

Can you do workspace.Print(workspace.abs_lines_per_species)?  If you have the 
mirrored lines, then they should be there, towards the end of the water tag.  
(It might be better to access these from the 
workspace.abs_lines_per_species.value if you have too many lines.  
workspace.abs_lines_per_species.value[N][M].lines [or something like that] 
should give you the lines of the M+1:th band of your N+1:th abs_species tag.  
The last of these for water should have negative values.)

(I think it would be better to set the mirroring tag to something like Lorentz 
using workspace.abs_lines_per_speciesSetMirroringForSpecies, since this should 
be the physically correct way of doing it.)


Den tors 17 mars 2022 kl 12:50 skrev Fox, Stuart 
Hi Richard,

I really don’t think there’s a copy/paste error – I am running exactly the same 
set of instructions (via pyarts) and I get the different results between the 
different ARTS versions.

Propmat_clearsky_agenda is:
and abs_xsec_agenda is:

Have you changed abs_lines_per_speciesMakeManualMirroringSpecies? (I am using 
this for the water vapour but not the ozone)?

I will look at putting together a simpler test case…

From: Richard Larsson <ric.lars...@gmail.com<mailto:ric.lars...@gmail.com>>
Sent: 17 March 2022 11:30
To: Fox, Stuart 
Cc: arts_dev.mi@lists.uni-hamburg.de<mailto:arts_dev.mi@lists.uni-hamburg.de>
Subject: Re: Help, something broke my simulations!

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links & attachments.
Hi Stuart,

I would need some way to test this to give any real answers.  For now I can 
only ask questions.

It looks like you are somehow computing the 183 GHz line twice.  This should 
not happen easily.  Have you somehow made a copy-paste error that still retains 
a "complete" model in this setup?

Are you using abs_xsec_per_speciesAddLines or propmat_clearskyAddLines?  (It 
would be fantastic if you are using both, because then the error would be 
exactly that, but your ozone lines make it look like you are not computing them 

There are some small changes in abs_xsec_per_speciesAddLines.  I don't think 
they should cause any issues, but change is change so it is a possibility.

With hope,

Den tors 17 mars 2022 kl 11:57 skrev Fox, Stuart 
Hi ARTS devs,

One of the recent-(ish) commits to ARTS has broken my simulations! With the 
current head of master I get big differences in simulated brightness 
temperature around a water vapour absorption line when I do simulations that 
also include ozone (blue line in attached plots), compared to simulations 
without (orange line). This didn’t use to be the case, at least back at commit 
3b6565f. Both water vapour and ozone in these simulations are calculated using 
absorption line catalogues rather than “complete” models – if I use a complete 
model for water vapour the problem goes away.

Before I spend a bit of time putting together a simple test case and/or trying 
to identify which commits caused the change, does anyone know already what the 
cause might be, and what I need to do to fix it (e.g. changes to controlfiles)?



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