Dear Shaofei Wang, I didn’t know what to make of your question 2, but a private mail from Patrick gave me the right clue.
I think the behaviour you see is correct, although unintuitive. The reason is that the self-broadening parameter of water vapor is a lot larger than its broadening parameters by other gases. With the Perrin catalogue that you use, broadening is specified explicitly for individual gases (no concept of abstract “air”). In order to make sure that the total broadening agrees with the total pressure, available broadening is rescaled if the given VMRs do not add up to 1. As a consequence, if you make a calculation for an atmosphere that is 100% H2O, it will effectively use the self broadening parameter together with the total pressure. The water lines then appear wider, but less intense in the center, as shown by your plot. The correct way to decompose absorption (or opacity) is to make the calculation with all species switched on. Then either look inside an absorption lookup table (which stores the species separately), or use the Jacobian feature. A third way is to use a special flag to the methods that go into the propmat_clearsky_agenda, which tells them to calculate only for one gas (while keeping the other for broadening). Or, simpler than all this if you just want to redo the figure with minimal effort, switch to a different line catalog that does not have “per species” broadening parameters. Either the Artscat in arts-xml-data or HITRAN should work. Those catalogs contain an “air” broadening parameter, that internally is multiplied with the total pressure, so the program will not notice that your VMRs do not add up to 1. Best wishes, Stefan On 21 Sep 2021, at 17:12, Shaofei Wang wrote: > Dear ARTS developers: > My name is Shaofei Wang, a graduate student from China. I'm very sorry > for bothing you. > Recently, i am studying ARTS. I simulated the optical depth of the > standard tropical atmosphere under clear-sky with ARTS (10-1000GHz). Please > see the attachment (.png) for the simulation results. > But I encountered two problems: > (1) When odepth is greater than 750, inf appears in odepth. I guess > this is due to the calculation accuracy of C++, but i am not sure. > (2) When only H2O is used as absorbing species, the optical depths is > sometimes greater than those when using N2, O2 and water as absorbing > species. This is very confusing to me. In my opinion, the optical depth of > the latter should always be greater than or equal to the former. I would like > to ask if there is a problem with my understanding or with my ARTS > controlfile. Please see the attachment (.arts) for the arts controlfile used. > I look forward to your reply to my email. Thank you again for your > contribution to ARTS！ > > Thanks in advance and Best Regards, > Shaofei Wang > > > 从 Windows 版邮件发送 > > _______________________________________________ > arts_users.mi mailing list > arts_users.mi@lists.uni-hamburg.de > https://mailman.rrz.uni-hamburg.de/mailman/listinfo/arts_users.mi _______________________________________________ arts_users.mi mailing list arts_users.mi@lists.uni-hamburg.de https://mailman.rrz.uni-hamburg.de/mailman/listinfo/arts_users.mi
