Questions about Transmittance Coefficient generation

Dear Sir/ma’am

My name is Haibo Zhao, I am a new user of CRTM 2.4, I am excited to find there are two folders “TauProd” and “TauRegress” contained in “src” folder, which appear to be functions of line-by-line calculation of IR/MW transmittance and ODAS/ODPS regression.

After further reading of 2.4 version user manual (D: Known Issues and Troubleshooting), I found: “1. Any ’Transmitance Coefficient’ generation codes included in src/ are not functional. Contact CRTM support above for details.”

Is there more detailed information about the development progress of those two functions, or to which degree they don’t work, or is it possible after some manual configurations I can get those two functions to work?

Thanks for your time,

Hi Haibo,

These folders are extraneous and do not provide the appropriate content for transmittance coefficient generation. The method for generating new transmittance coefficients is simple in description, but difficult in execution. It requires intimate knowledge of LBLRTM, and requires specific detailed information how to create the regression coefficients for various atmospheric species. IF you’re only interested in microwave sensors, then it’s a bit easier and doesn’t require LBLRTM.

If, however, you wish to continue, please contact Patrick Stegmann ( and he can assist you with obtaining some codes and will provide some directions. Any coefficient files that you create that are used in publication or operational implementations, we request that you share these with us to ensure consistency and traceability and you should identify these in publications as “experimental” since they are not part of the official CRTM release.

Kind regards,

CRTM Project Lead

Hello Haibo,

thank you for your interest in the CRTM.

As Ben already mentioned, correctly computing new spectral and transmittance coefficients for the CRTM is a very complex process.
For this reason the current version of the respective code has restricted access for CRTM expert users only and in your case we may also have to consider export control restrictions.

Until a final release of the code becomes available, we can alternatively offer to compute the transmittance coefficients for you. All we need is the spectral response function (SRF) of your instrument.

Hello Haibo,

thank you for your email response.
I will contact the RTTOV team and ask whether they have SRFs for FY-3C/D MWTS MWHS MWRI.

Hello Haibo,

unfortunately it seems that the RTTOV team also does not have access to the respective SRF.
Perhaps you can contact one of the members of the instrument team.

Please also place any future answers in this thread.