CMA: Scott Hu
CNES: Clemence Pierangelo
ECMWF: Dave Duncan
ESA: Stefano Casadio, Fabrizio Niro
EUM: Dorothée Coppens, Tim Hewison, Rosemary Munro, Viju John
JMA: Kazutaka Yamada, Hideaki Tanaka, Arata Okuyama, Kazuki Kodera
KMA: Dohyeong Kim, Minju Gu, Wonhyeong
NASA; Ben Scarino, Dave Doelling
NOAA: Likun Wang, Fred Wu, Manik Bali, Fangfang Yu, Larry Flynn
UCAR: Greg Kopp
WMO: Heikki Pohjola
This has been a CGMS Best Practice for IR and MW instruments since CGMS-44
Accurate SRFs are increasing vital to support microwave spectral management
He also showed examples of where NWP statistics benefits from use of detailed SRFs, instead of approximating them as simple Top-hat functions, as has been done
He went on to review the proposed actions to be considered by CGMS:
CGMS Members shall ensure that accurate channel Spectral Response Functions (SRFs) for all microwave and infrared instruments are measured and made available as described in the CGMS Best Practise.
CGMS Members shall also make available their validated instrument SRFs together with uncertainty information through their instrument calibration landing pages. In addition, a document summarizing the currently available SRFs and their status (accurate/inaccurate) as well as identifying any missing information shall be provided through the landing pages.
it was noted that these information could be made available through OSCAR instrument landing pages
WMO will establish links to this information through the relevant instrument entries in the OSCAR/Space database. This information will be updated with the help of the OSCAR/Space Support Team though the regular requests for satellite status updates.
Definition of precise? High-precision pre-launch knowledge
The difficulty of diagnosing whether the root cause of observed bias patterns are radiometric calibration or spectral characterisation was recognised. It was pointed out that while SRF shifts may be easy to characterise, changing SRF shapes are less so.
The applicability of NWP bias monitoring statistics to investigate the SRF of infrared window channels was discussed, but felt to be difficult due to the lack of atmospheric signal.
The question of how to specify and use SRF uncertainty information remains open. It was suggested that offline studies could be run using RTMs, and that a GSICS convention could be established to provide SRF uncertainty information
The spectral resolution needed for SRFs depends on the channel, but may require tens to hundreds of wavelengths spread across the passband. Again, it was suggested that offline studies could be run using RTMs.
Furthermore, it was pointed out that SRF may need to be characterised across the full spectrum (especially in the reflected solar band) due to sensitivity to out of band signal.
Instrument manufacturers would appreciate guidance on what should be avoided - e.g. sensitivity to particular atmospheric lines.
Greg pointed out CLARREO studies, which showed inter-calibration uncertainty can be dominated by SRF uncertainties.
WMO plan to start monitoring the availability of SRF info
Action: A.GRWG.20200618.1: Tim Hewison (EUMETSAT) to consider providing FCI SRF uncertainties to ECMWF for analysis
Discussions lead to the following recommendations for the workshop:
1) NWP to define the minimum level of uncertainty on the SRF (e.g. accurate and resolution requirements) from the workshop and provide the feedback to the GSICS community.
2) NWP to define the minimum level of uncertainty on instrument's calibration from the workshop and provide the feedback to the GSICS community - this may provide focus for GSICS future developments.3) NWP community to communicate with the instrument manufacturers to avoid adverse spectral range observed with the assimilation results.
NWP can provide GSICS with feedback on the bias correction applied in the assimilation of GSICS Reference instruments (IASI, CrIS, AIRS, …)
And could potentially contribute to the IRRefUTable report
...and observations found to have negative impact on NWP (e.g. due to large or unstable error characteristics)
Seek feedback from the NWP community on the use of FCDRs as inter-calibration references - e.g. could inter-calibration products derived from such algorithms be useful in NWP Re-Analysis campaigns?
Seek feedback from the NWP community on the minimum acceptable level of bias in observations
In general, we should aim for consistent treatment of systematic, random and structure errors - including timescale and spatial dependence in NWP and GSICS communities.
Can GSICS provide information to help determine whether observed biases are due to radiometric calibration or spectral characterisation errors?
e.g. SRF retrievals based on comparison with hyperspectral references, Diagnose whether observed bias patterns consistent with SRF shifts, etc
|pptx||ECMWF Error Workshop - GSICS Feedback.pptx||manage||2 MB||18 Jun 2020 - 08:29||TimHewison|
|GSICS_SRFs_180620_Duncan.pdf||manage||1 MB||18 Jun 2020 - 08:08||TimHewison|
|pptx||Kopp_SITSAT_Workshop.pptx||manage||20 MB||18 Jun 2020 - 14:33||TimHewison|