Hi again,

We were not aware of the first point, but this indeed look like an issue of numerical precision.

We derive tau from transmissivity. I did a test in Matlab. exp(-740) is > 0, while exp(-750) gives 0. This fits what you report reports, that optical thicknesses above 750 can not be reconstructed from the transmissivity, as it has become zero.

Bye,

Patrick



On 2021-09-21 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 <https://go.microsoft.com/fwlink/?LinkId=550986>发送


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