Documentation RTTOV coefficients

[Bart Quaink]

I am looking at the coefficient files now to get some better insight in what these files do and how they work. I was wondering if there is some sort of documentation on the format specification and use of the coefficient files? I can’t find any specific documentation about this on the coefficient download page. Specifically I am looking at the IASI coefficient files.

I tried to get in contact with Ghislaine at CNES, but it seems the mail provided in the hdf5 README is not in use anymore.

Another sidething: I tried to post this in the V13 forum, but I cannot make new topics there. Not sure what the issue is.

Thanks!

[James Hocking]

Hi Bart,

You can print out summary information about a coefficient file using the rttov_coef_info.exe executable that is built as part of RTTOV (see Annex A in the user guide).

In general I wouldn’t recommend getting bogged down in the detailed contents of the files: we don’t provide documentation on the format/contents of the files because it is not really relevant to users.

There are various sources of information on the science in RTTOV. If you want to know more about the optical depth regression, I would recommend the recent summary paper on RTTOV which gives further references if you want to understand all the details:
https://doi.org/10.5194/gmd-11-2717-2018

The coefficient files also contain coefficients for other parameterisations such as the IR sea surface emissivity models. If you want to know more about these and other features of RTTOV, I would recommend the RTTOV Science and Validation Reports which document the science in the model. For example, the RTTOV v12 and v13 SVRs are available here:
https://nwp-saf.eumetsat.int/site/download/documentation/rtm/docs_rttov12/rttov12_svr.pdf
https://nwp-saf.eumetsat.int/site/download/documentation/rtm/docs_rttov13/rttov13_svr.pdf

The Spectral Response Function section of the files records information about the spectral response data used when generating the coefficients, and often refers to the source of the information. The people who provide us with spectral response information do not have anything to do with the generation of the coefficient files themselves: we (the NWP SAF) generate all of the (official) coefficient files for RTTOV. If you have specific questions about the coefficient files, feel free to ask here or via the help desk.
https://nwp-saf.eumetsat.int/site/help-desk/

I created the new RTTOV v13 forums recently, and one user has been able to post in the “General Discussion” forum. If you are still unable to post there, I will follow this up with our web admins.
https://nwp-saf.eumetsat.int/site/forums/forum/rttov/rttov-v13/rttov-v13-general-discussion/

I hope that helps, but let us know if you have further questions!

Best wishes,
James

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