# Question about the process of CRTM coefficient files

**URL:** <https://forums.jcsda.org/t/question-about-the-process-of-crtm-coefficient-files/736>\
**Category:** CRTM\
**Created:** [April 2, 2026, 7:47am UTC](https://forums.jcsda.org/t/question-about-the-process-of-crtm-coefficient-files/736 "2026-04-02T07:47:32Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![chaochao](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.jcsda.org/chaochao/32/280_2.png) [@chaochao](https://forums.jcsda.org/u/chaochao)\
**Post date:** [April 2, 2026, 7:47am UTC](https://forums.jcsda.org/t/question-about-the-process-of-crtm-coefficient-files/736/1 "2026-04-02T07:47:32Z")

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Dear Sir/Ma’am,

Hello, this is chaochao. I am currently working on the data assimilation of the FY-3F Microwave Humidity Sounder (MWHS-2). Since the CRTM coefficient files for this instrument are not publicly available, I referred to the CRTM\_coef tool you shared in the Git repository and followed the manual to generate the spc and tau files.

However, when running GSI assimilation experiments with these coefficients, I found that the OMB (Observation minus Background) shows a large bias, on the order of several tens of Kelvin. I suspect that there may be an issue with the tau file I generated. Could you kindly provide some guidance or assistance?

For your convenience, the spc and tau files are provided below. I look forward to your reply. Any help or suggestions would be greatly appreciate d.

My email is [daoheheo@163.com](mailto:daoheheo@163.com)

The coefficient related documents I made are in [https://github.com/daohehe/crtm\_coef\_tst/releases/tag/v1](https://github.com/daohehe/crtm_coef_tst/releases/tag/v1)

Sincerely,

chaochao