Dear Patrick, Thank you for this clarification.
I will see if I manage to remove the differences with your suggestions. But as you think it is not important, I will not spend too much time on it. We are comparing ARTS with another radiative transfer model and I was used to simulate my spectra with Qpack. But then I used arts to simulate monochromatic pencil beam spectra as suggested by Ole Martin. And as I saw differences between the two calls I was a little bit worried. For me, ARTS is a little bit tricky and I did not want to have differences between my two radiative transfer models due to a bad use of ARTS. But I will test your suggestions and see what happens. Thank you again. 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 ----- Mail original ----- De: "Patrick Eriksson" <[email protected]> À: "Pauline Martinet" <[email protected]> Cc: [email protected] Envoyé: Lundi 7 Septembre 2015 20:53:30 Objet: Re: [Qpack] differences between Qpack and arts simulation Pauline, Let me first say that I don't think the differences you find are of any practical consequences, so probably not an "error". But I like that you are so careful. First I must ask where you found that qpack2 should mimic arts_y exactly? This is basically, true but there some subtle differences around HSE (and that qpack uses automatically the ATMDATA fields). > - T field identical to the first dimension of Q.T.ATMDATA.DATA Is Q.T.ATMDATA.DATA then just a vector? Otherwise this is not a sufficient criterion. If you want to check, this is what qpack does to set Q.T_FIELD: Q.T_FIELD = qarts_atm_field( Q, 't', mjd, ho ); where mjd and ho are set based on data information in Y. > - VMR field identical to the ABS_SPECIES.ATMDATA.DATA : ok Same comment here. > - Y.HSE_P equals to Q.HSE_P This part is more tricky. First of all, if you have HSE.ON=true, Y.HSE_P and Y.HSE_Z will result in an altitude profile, that overwries anything you have in Q.Z_FIELD and Q.Z.ATMDATA. I will make this clear in qpack2.pdf (for v2.3). With HSE.ON = true we have in fact a difference between running qpack and arts_y. To mimic exactly what qpack is doing you need to do Q.Z_FIELD = qarts_hse( Q, Y.HSE_P, Y.HSE_Z ); As you noticed, there is no Q.HSE.Z. When running outside qpack2, "HSE_Z" is taken from Z_FIELD by interpolation to HSE_P. And you have likely a small difference between Q.Z_FIELD and the Z_FIELD produced by qarts_hse. If you set Q.Z_FIELD and set Q.HSE.ON=false (and don't set Z.ATMDATA), you should use identical altitudes both when running qpack2 and arts_y. I hope this clarified things around HSE!? > - Y.ZA is equal to Q.SENSOR_LOS (for the zenith angle) > - Q.SENSOR_POS equals Y.Z_PLATFORM OK Bye, Patrick _______________________________________________ qpack mailing list [email protected] https://www.sat.ltu.se/mailman/listinfo/qpack
