GRWG IR Sub-Group Web Meeting 2018-11-14

GSICS web meeting on IR Reference Uncertainty & Traceability Report (IRRefUTable)

Agenda

• Tom Pagano (JPL) - New AIRS calibration and uncertainty estimate - presentation, paper
• Tim Hewison (EUMETSAT) - Update on plans for IRRefUTable Report
• All - Review format and contents of uncertainty tables following Tom's example for AIRS
• Manik Bali (NOAA) - Double difference of AIRS and IASI-A against AATSR

The following items were postponed from the last web meeting on this topic 20170620:

• George Aumann (JPL) - Validation of AIRS calibration - TBC
• Denis Jouglet(CNES) - Inter-comparison uncertainty budget - TBC
• Dave Tobin (NOAA/SSEC) - Tabulation of inter-comparison results - TBC

Attendees

Guest Chair: Tim Hewison

EUMETSAT: Tim Hewison, Dorothée Coppens

KMA: Hyeji Yang

NASA: Tom Pagano, Chris Wilson, Ben Scarino

NOAA: Likun Wang, Manik Bali, Fangfang Yu

RAL: Dave Smith

SSEC: Joe Taylor

UMD: Hui Xu

Summary

Tom Pagano presented v7 of the AIRS calibration, which is expected to be available from 2019Q4 as a reprocessed dataset, superseding the current v5. The biggest changes wrt v5 are in the shortwave cold end (differences up to 1K), with smaller differences in the long-wave band (~0.1K). It now agrees very well with CrIS - within the uncertainties. The question was raised whether this version of the calibration would eventually be used in operations. Tom pointed out that while this is decision is up to operator, the main operational application of AIRS is in data assimilation, which uses its own bias correction schemes.

Tom also presented the uncertainty analysis that accompanies the v7 AIRS calibration. This results in more uniform uncertainties across spectral and radiance-space. It was discussed how to include these new results in the IRRefUTable Report.

Tim Hewison reviewed the (slow) progress with the IR Reference Uncertainty and Traceability ( IRRefUTable ) Report and asked for confirmations of contributions. Dorothée Coppens offered to provided results for inter-comparisons using the “massive means” and “Obs-Calc” methods - at least between IASI-A, -B and -C - and potentially CrIS . The date range for the comparison was also discussed, as the delay has allowed inter-comparisons with other instruments (NOAA-20/CrIS, FY-3D/HIRAS and Metop-C/IASI) to be considered.

Manik Bali reviewed an analysis of inter-comparisons of AATSR and AIRS and IASI-A. The ATSR series could be considered as a valuable reference for the inter-calibration of heritage multispectral sensors with similar SRFs. The problem of considering as a contribution to the IRRefUTable report is the available date range. However, the analysis could be repeated with other hyperspectral reference instruments using SLSTR on Sentinel-3A and/or -3B. A counterpart report on multispectral reference instruments suitable for the re-calibration of heritage instruments was identified as a useful future activity.

Actions:

A.GIR.20181114.1: Tom Pagano to provide output of uncertainty analysis for v5 and v7 AIRS calibration averaged in radiance and spectral bins recommended for the IRRefUTable report.

A.GIR.20181114.2: Tim Hewison to solicit available date ranges from IRRefUTable contributors, with the aim of finalising a decision by 2019-03-01.

A.GIR.20181114.3: Manik Bali and Tim Hewison to draft a section of the IRRefUTable Report on the process of selecting a reference instrument.