All non-Zeeman MW coefficients updated

[Anonymous]

Dear RTTOV users,

Due to a major review of the microwave line by line code and procedures a number of bug fixes and improvements have been carried out, and as a result all non-Zeeman microwave coefficients have been regenerated, with new Zeeman coefficients to follow.

A detailed description of the changes, along with statistical plots indicating the affect on simulated brightness temperatures, can be found here:
https://nwp-saf.eumetsat.int/site/software/rttov/download/coefficients/detailed-file-history/#20160526_mw

The new coefficients can be found here:
https://nwp-saf.eumetsat.int/site/software/rttov/download/coefficients/coefficient-download/#MW_optical_depth_coefficients

Summary of main changes:

– Correction of a bug in the microwave line by line model affecting a number of sensors. The largest errors are seen in ATMS, MWS and SSMIS with brightness temperature differences of around 0.5K in some channels.

– Temperature dependence of the 183GHz Water Vapour line halfwidth has been updated to that in Payne et al (2008). This results in differences of order 0.1K in brightness temperatures for 183GHz channels.

– Due to a bug in the coefficient generation proceedure code, the channel specifications in the FILTER_FUNCTIONS header section of the rtcoef_noaa_18_mhs.dat and rtcoef_noaa_19_mhs.dat coefficient files were incorrectly listed as those for AMSUB, for which channels 2 and 5 are significantly different (note this did not affect the coefficients themselves). This has now been corrected.

– Changes to filter files: MWS updated to latest available specifications, minor modifications to SSMIS to bring it in line with specified values for sensor SN01 (DMSP-20), and minor corrections due to precision errors in other filter files.

As always, any questions or comments are welcome via the NWPSAF Helpdesk or the forum:
https://nwp-saf.eumetsat.int/site/helpdesk/
https://nwp-saf.eumetsat.int/site/forums/

Best regards,
RTTOV development team

[Author]

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