GSICS IR Reference Uncertainty & Traceability (IRRefUTable) Report

A project of the GRWG IR Sub-Group

Report under development in Zoho:

Database under development in Zoho:


•To support choice of reference instruments for GSICS and Metop-A/IASI as Anchor

•To provide traceability between reference instruments (IASI, AIRS, CrIS)

•By consolidating pre-launch test results and various in-flight comparisons

•To seek consensus on uncertainties in absolute calibration of reference sensors


•No new results, just expressing results of existing comparisons in a common way,

•reformatting where necessary, to allow easy comparisons

•Error Budget & Traceability

•Focus on radiometric and spectral calibration – for AIRS, IASI, CrIS


•Introduction: Pros and Cons of each method

•Direct Comparisons: Polar SNOs, Tandem SNOs (AIRS+CrIS), Quasi-SNOs,

•Double-Differencing: GEO-LEO, NWP+RTM, Aircraft campaigns

•Other Methods: Regional Averages (“Massive Means”), Reference Sites (Dome-C..)

Discussed at the following GSICS Meetings:

GRWG/GDWG: AnnualMeeting2019 - agenda item 7g

IRSG Web Meeting: 2018-11-14

GRWG/GDWG: Annual Meeting 2018 - agenda item 4p

IRSG Web Meeting: 2017-06-20

GRWG/GDWG: Annual Meeting 2017 - agenda item 7d

IRSG Web Meeting: 2016-09-08

IRSG Web Meeting: 2016-06-21

GRWG/GDWG: Annual Meeting 2016 - agenda item 3 q

  • It was agreed to report the uncertainties and relative differences between sensors as brightness temperatures differences,
  • evaluated for scenes ranging from 200-300K at 10K intervals,
  • and at 10cm^-1 intervals, calculated from hyperspectral radiances, following the methodology previously described by Denis Jouglet,
  • D.GIR.2019.7g.1: It was agreed to use the 4-year period 2013-03/2017-03 for the initial IRRefUTable analysis to be performed in 2019,
    • then aim to issue an update in late 2020 to include at least 1 year of data with IASI-C, N20/CrIS and HIRAS.


A.GIR.2019.7g.1: Mitch Goldberg (NOAA) to confirm the person to provide NWP and SNO method results to IRRefUTable report.
A.GIR.2019.7g.2: Bill Bell (ECMWF) to consider providing results from ERA-5 to IRRefUtable report.
A.GIR.2019.7g.3: Mitch Goldberg will provide the document or information on CrIS operational data change during CrIS operational time.

Key Contributors:

Error Budget & Traceability

•AIRS – Tom Pagano

•CrIS – Dave Tobin

•IASI – Clemence Pierangelo (replaces Denis Jouglet)


Polar SNOs: Clemence Pierangelo (replaces Denis Jouglet), Dave Tobin, Likun Wang

•Tandem SNOs: Dave Tobin

•Quasi SNOs: Clemence Pierangelo (replaces Denis Jouglet)

GEO-LEO Double Differencers:

•Tim Hewison (EUMETSAT), Masaya Takahashi (JMA), Fangfang Yu/Fred Wu (NOAA)

•Hanlie Xu / Na Xu (CMA), Minju Gu (KMA)

NWP Double-Differencers:

•TBC? (NOAA), Chengli Qi (CMA), Bill Bell (ECMWF)?

Aircraft Double-Differencers:

•Joe Taylor?


-- TimHewison - 31 Oct 2018
Topic revision: r6 - 08 May 2019, TimHewison
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