GRWG Web Meeting 2015-11-03

GSICS GRWG VIS/NIR Sub-Group Web Meeting on DCCs

Agenda

1. Dave Doelling (NASA) - GSICS DCC calibration update
2. Masaya Takahashi (JMA) - DCC product Requirements for GSICS Plotting Tool
3. Manik Bali (NOAA) - GPPA Review of EUMETSAT DCC Demo Product
4. Tim Hewison (EUMETSAT) - Review of EUMETSAT DCC Demo Product

Attendees

Guest Chair: Dave Doelling (NASA)

NASA: Dave Doelling, Amit Angal

EUMETSAT: Tim Hewison, Sebastien Wagner and later, Bartolomeo Viticchie

JMA - Masaya Takahashi

KMA: Dohyeong Kim, hyesook Lee, Taehyeong Oh, Minju Gu, Hyeji Yang

NOAA: Manik Bali

UAH: Dennis Buechler

Summary

Plotting Tool – it was confirmed that the plotting tool should be able to generate time series plots of nominal and corrected calibration coefficients (gains) and biases, as well as their uncertainties. It was felt that while GPRCs should also monitor the PDFs of DCC distributions as intermediate products, these should not be necessary for the users.

Action: Masaya Takahashi and Sebastien Wagner will draft requirements for application of plotting tool to DCC products for presentation at 2016 GRWG meeting.

Quality Control – different approaches to provide this important information to the users were discussed. It was agreed that the uncertainties of the calibration coefficients should be provided, together with clear guidance on how to apply them.

Action: Tim Hewison to the User Guide for EUMETSAT GEO-LEO IR products includes clear guidance on how to use the GSICS Corrections’ uncertainties as quality control.

Update Frequency – It was clarified that this is distinct from the window period. The preferred approach was to issue frequent updates, together with uncertainties. This was to avoid step functions or discontinuities in the GSICS calibrations. Since real time users have scripts to download files, a consistent update frequency is desired. If there is an unscheduled calibration update, this will need to be a manual update for users, which is burdensome.

The Update Frequency is distinct from the windowing period. It was agreed that the GPRC would decide their own windowing period, outlier removal and trend analysis of the DCC observations to provide users the resulting calibration coefficients. The windowing periods are unique to every GEO domain.

GSICS Corrections – It was agreed that the GSICS Corrections should be provided to correct the instruments’ nominal calibration to be consistent with the reference. If the nominal calibration is based on Solar Diffuser views, these would generally be applied before the GSICS Correction.

GSICS Procedure for Product Acceptance – Tim proposed that GRWG, GDWG and Sub-Group Chairs should be listed as members of the GPAT. Dave has agreed to review Sebastien’s DCC demo product.

Follow-up Meetings – GSICS DCC web meeting is planned for late January 2016. This will include an analysis of the DCC results from multiple channels of Himawari-8 by JMA and a comparison different BRDF models by KMA. Also deseasonalization methods and angular thresholds to limit the DCC to the more Lambertain part of the BRDF, presentations will be greatly appreciated.

GSICS annual meeting will be held in early March 2016. Amit Angal will also present a comparison of DCC results from MODIS and VIIRS, including other channels. We will begin discussing the transition from MODIS to VIIRS of the visible reference calibration.

Action: Manik Bali to draft a strawman proposal on consistent naming convention of GSICS Products and present this at the 2016 annual meeting. Dave suggested this start with GSICS, followed by the name of the Monitored instrument – e.g. GSICS Correction/Calibration of [Monitored Instrument] (to [Reference Instrument]) (using [Method]) – but should it include the GPRC? Soon we will have a long list of GSICS products on the web-ordering tool. The web-ordering tool has a filename search. Therefore it should be easy for the user to differentiate between the monitored and the reference instrument in the filename.