Hi Stuart, I see. I think I need yet another update in the future because I don't support mirroring in the way you want to use it (which is how ARTS 2.3 did it, so it should probably return).
My intention with the "Manual" option was just to allow checks of negative line centers to pass. My intent was that you as a user had mirrored not just the central frequency but also the line shifts, as these are shifting in the wrong direction for the mirrored line. However, this is actually not how 2.3 did it. In 2.3, the direction of the shifts were based on the sign of the frequency. So manually mirrored lines must manually mirror themselves. So two changes must be made on my side: 1) Manual mirroring should return to use options as in ARTS 2.3. 2) The checks on the cutoff should fail for any type of active mirroring bar Manual. Give me some hours to prepare a patch and the hours/days/weeks it takes for this to merge. With hope, //Richard Den tors 10 juni 2021 kl 10:29 skrev Fox, Stuart < stuart....@metoffice.gov.uk>: > Sorry – for v2.5 I should have said I’m seeing differences between > mirroring_option=”SameAsLineShape” and mirroring_option=”Manual”. > > > > *From:* Fox, Stuart > *Sent:* 10 June 2021 09:26 > *To:* Richard Larsson <ric.lars...@gmail.com> > *Cc:* arts_dev.mi@lists.uni-hamburg.de > *Subject:* RE: ARTS line absorption v2.3 vs v2.5 > > > > Hi Richard, > > > > Thanks very much for your reply. I expect the difference I’m seeing > between the versions when there’s a normalization factor and a pressure > shift is due to the calculation of the normalization factor on the > unshifted frequencies. I don’t know enough about the physics to comment > which is more appropriate. > > > > However, I still don’t understand the differences I’m seeing with the > mirror lines, as they are there even with no cutoff and no forefactor. In > v2.3 I get identical results if I use: > > 1. abs_lines_per_speciesAddMirrorLines with a single line with no > pressure shift @ H2O-161 183310107053.569 0.0 2.3119066399931e-16 296 > 2.70486699225234e-21 30326.8955785838 153557.646880829 0.71 0.71 296 0 > 3000000 0.1 0.05 0.05 -1 -1 -1 > 2. a manual mirror line: @ H2O-161 183310107053.569 0.0 > 2.3119066399931e-16 296 2.70486699225234e-21 30326.8955785838 > 153557.646880829 0.71 0.71 296 0 3000000 0.1 0.05 0.05 -1 -1 -1 > > @ H2O-161 > -183310107053.569 0.0 2.3119066399931e-16 296 2.70486699225234e-21 > 30326.8955785838 153557.646880829 0.71 0.71 296 0 3000000 0.1 0.05 0.05 -1 > -1 -1 > > In v2.5 these two line files give different results (when the first is > applied with mirroring_option=”None” and the second with > mirroring_option=”Manual”) > > > > Note that I’m doing these tests with a Lorentz line shape, so the > differences in the Voigt function shouldn’t matter. > > > > Thanks for your time, > > > > Stuart > > > > *From:* Richard Larsson <ric.lars...@gmail.com> > *Sent:* 09 June 2021 17:01 > *To:* Fox, Stuart <stuart....@metoffice.gov.uk> > *Cc:* arts_dev.mi@lists.uni-hamburg.de > *Subject:* Re: ARTS line absorption v2.3 vs v2.5 > > > > *This email was received from an external source. Always check sender > details, links & attachments.* > > Hi Stuart, > > > > All the differences between current 2.5 version and old version that I can > think of are: > > > > The Doppler broadening is computed on shifted frequencies instead of on > unshifted frequencies. This should be more accurate as far as > I am concerned. > > > > The normalization factor is computed on the unshifted frequencies instead > of on the shifted frequencies. If I have not misunderstood the > normalization factors, this should also be closer to the physics since you > shouldn't really be scaling the line strengths with the line frequency but > by the atmospheric frequency (as in the new LM code). This is potentially > an issue. > > > > The line shape can no longer be a speed-up Voigt function but you have to > use the full calculations. The old code was wrong at a scale of 1e-6 if I > understand the old comments. > > > > The new code does the mirroring inline unless manually added to the > catalog. Before you had to manually add a new line with negative line > center. It is possible there's a bug here, since I haven't tested this so > accurately before. This changes the cutoff frequency since the old code > cutoff at CUTOFF - F0 instead at F0 + CUTOFF for the inline mirrored > lines. (Thinking about it practically, this makes the line shape > non-symmetric, so I will have to add a check to the lbl-check that there's > no cutoff used when mirrored lines are there by inline instead of by > copy-pasta.) I would think that the difference in cutoff here is the main > difference you are seeing. > > > > I think that's about it. There's of course entire different algorithm > involved, so some additional differences may be from there. > > > > With hope, > > //Richard > > > > > > > > Den ons 9 juni 2021 kl 17:21 skrev Fox, Stuart < > stuart....@metoffice.gov.uk>: > > Hello all, > > > > Thanks for all the work on the line cutoff behaviour in the latest version > of ARTS! However,I’m still struggling to reproduce the absorption line > behaviour between v2.3.1277 and v2.5 even after the latest work on the line > cutoff from Richard. In fact, even without a line cutoff there still seems > to be differences caused by (i) the interaction between a line > normalization factor (e.g. VVH) and the line pressure shift, and (ii) the > treatment of mirror lines. > > > > A simple example of (i) using only a single water vapour line with a > Lorentz profile and VVH pre-factor can be found here, with differences up > to about 0.08K: > > https://github.com/stuartfox/arts-cutoff-problem/tree/single-line > > > > For (ii), if I set the normalization to None but add the mirror lines > (with the SameAsLineShape option) I get differences of 0.001K in this test, > but much larger values in a more realistic case with more lines (0.5-0.6K > below 100GHz). > > > > I’ve no idea which version is more correct, but it would be nice to > understand the causes of these variations! > > > > Thanks for all your help, > > > > Stuart > > > > > >
