Chair: Tim HewisonEUMETSAT : Tim Hewison, Viju John
CMA: Chengli Qi
NOAA: Xiangqian(Fred) Wu, Manik Bali, Lawrence E Flynn, Fangfang Yu, Ken Knapp
NASA: Dave Doelling, Ben Scarino, Raj Bhatt
JMA: Arata Okuyama, Hideaki TanakaKMA: Minju Gu, Wonhyeong, Jin Woo
ISCCP-NG is creating an excellent platform for testing and using GSICS products and algorithms. ISCCP-NG wants to be a GSICS customer
ISCCP-NG will start to generate common cloud products from the common channels of the advanced GEO imagers operational in ~2023
ISCCP-NG may include reprocessing of legacy sensors’ archive data later
It is critical to GSICS that we receive feedback from ISCCP-NG on the definition and use of GSICS products
All GSICS agencies operating advanced GEO imagers should present plans to develop calibration monitoring and correction for their common channels at the 2021 annual meeting
By Andrew Heidinger (NOAA) Presented by Ken KnappThe presentation began with the ISCCP-NG meeting in EUMETSAT. It was mentioned that ISCCP-NG (Next Generation) is a follow-on from the classical International Satellite Cloud Climatology Project (ISCCP), which aimed at producing cloud climatologies from the legacy satellites starting from AVHRR. With the advent of the next generation GEO and LEO satellites, ISCCP-NG aims to develop new algorithms to exploit their new common channels to improve its long-term cloud products.
ISCCP-NG is a rethinking as we have common channels across multiple satellites.
Andy Heidinger is an advocate of the L1g ( L1 gridded ) data set.Tim: Are you going to change the name of ISCCP-NG.
Tim: At the EUMETSAT ISCCP-NG meeting we discussed the remit of producing NRT or RAC, which one would be preferable?
Ken: This is up for discussion, as it relates to the latency in the processing chain
Tim: Lead time of GSICS product production is important.
Dave Doelling: There are two VIIRS (NPP and N20). The calibration for these two VIIRS are different. GSICS VIS/NIR recommends using N20-VIIRS as the VIS/NIR reference. When you do cloud properties, there is no azimuth angle dependence as in GEO. How do you address this? Which one takes precedence VIIRS or GEO?
Ken: The last meeting focused on using GEO as a reference however Its an ongoing discussion.
By Tim Hewison, EUMETSAT
Tim gave an overview of GSICS product status for GEO imagers, emphasizing that we still have work to do to be useful to ISCCP-NG. However, for the IR channels, this is already underway - e.g. KMA is preparing the KOMPSAT-2A product.
Tim then gave an overview of the ISCCP-NG discussion. A key point is the distinction between GSICS monitoring and applying/using GSICS correction. For instance, if you are monitoring the instrument, do you (still) need a correction if biases are small?
How should biases be corrected? (at the count level, radiance level or Brightness Temp level). How should the correction coefficients be distributed? (Should they be embedded in monitored instrument L1 data file e.g. MSG -x L1B ) or provided separately as a GSICS product data file or both.Dave: How does ISSCP plan to achieve sensor homogenization?
Dave: CLARREO's launch will give a boost to tying measurements to traceable reference.So far we have targeted to correct all GEO imagers for monitoring their biases Tim: Will ISCCP-NG focus on all GEOs or just operational ones?
Tim: We need inter-calibration products for all Solar channels
Tim: How do we archive data?
Ken: It is up to agencies to archive data.
Dave Doelling: How are counts and radiances related to new and old GEO?
Fred Wu: This relation is updated at every solar calibration. If we are calibrating to radiance then the solar spectrum matters. As long as this is not changed (e.g., if VIIRS and GEO use the same solar calibration spectrum).
Arata: We have two sets of coefficients: 1) count to radiance fixed 2) Correction coefficients to reflect solar diffuser calibration
Dave: Then we have to work on arriving at a common method
Arata: GSICS corrections we apply on the former (1), which uses corrections to the solar diffuser.
By Andy Heidinger, NOAAKen gave Andy’s presentation. The ISCCP-NG wish list is comprehensive. Some of the wish list items are already addressed. In summary, the wish list is levied on both GSICS as well as ISCCP-NG. That is what can/should GSICS deliver/provide to ISCCP-NG and conversely what should ISSCP-NG deliver to GSICS.
Some of the points listed in the wish list are
We would like to have corrections as attributes in our L1g which operate on
We would like IR Radiance in the standard unit for all sensors
We would like to have corrections that are of the same form for all sensors.
We would like standard radiance to temperature parameters which we will include as attributes.
Dave: In the end, cloud retrieval is done in Brightness Temperature Space
Ken: Can GSICS make finding data files are easy?
By Ken Knapp, NOAA
Timeliness and latency
When are GSICS corrections available vs. ISCCP-NG needs.?
ISCCP-NG still needs to define Timeliness requirements
ISCCP-NG interim iCDR may be released first then a final ISCCP-NG products
Will continue as long as the team is supported at NCEI and providers send data
in the early stages of testing VIIRS integration
Should we try to run ISCCP using GSICS calibration corrections? (VIS and IR needed)
Has access to GSICS corrections changed?
Radiance → Brightness temperature - How is that provided?
Equations? [Many satellite providers follow this approach]
LUT? [VIIRS does this]
ISCCP historically has centralized the calibration.
A decentralized calibration approach increases risk
Ken also suggested a path forward:
Agree on structure for corrections first
Answer many of Andy’s questions regarding correction type, channels, etc.
Move out in parallel
ISCCP NG begins work on developing GEO Level 1g
GSICS expands to provide corrections for necessary channels
ISCCP-Classic would continue. There is a plan to use GSICS Coeff in the classic.
Radiance to BT conversion process needs to be harmonized
Fred: From a perspective of reprocessing, realized many calibration deficiencies during reprocessing. We don’t have a plan to correct the calibration. Would like to collaborate with ISCCP-NG to correct calibration.
Dave: Could one save L0 data and apply a calibration model.
Fred: Technically this approach is straightforward for radiometric calibration. But the magnitude of data is enormous so it is just a scale problem.
Dave: In the future as the computing power grows we would like to do this.
Fred: We didn’t use to archive L0 data. As we move to cloud this could be possible as a project.
Dave: This could be made as an on order biases and one can easily implement version control. One can make online. Do you think geometric updates are needed more frequently?
Fred: If you wish to apply for geometric as well as radiometric then it is time-consuming. it uses INR
By Manik Bali and Larry Flynn, NOAAThe presentation was in response to the feedback Ken Knapp presented when he tried to access and use GSICS products at the 2019 GSICS Annual Meeting. Some of these can be summarized as
Files behind a TDS make it difficult to perform bulk downloads
It was not immediately clear what all the links were and which were useful and which were dead ends.
ATBDs are prominent but are less useful to end users (initially).
User guides are especially helpful but are more difficult to access.
The adjustments provided do not also provide the calibration coefficients
Leaving the user wondering “Am I using the right calibration coefficients??”
The GSICS websites appear to be developed for GSICS contributors not for users.
Scripts to download GSICS products have been developed at EUMETSAT (Python by Peter Miu) and NOAA (bash wget script Manik Bali).
Manik went on to show how to access and open GSICS product data files online. He recommended that in order to use GSICS products it is important to start with the User Guide. A good point to start is products with Pre-Op maturity.All the products are updated daily.
Ken: Is there a way to get the status of update of products?
Manik: Yes there are two ways. 1 ) Quicklooks 2) registering on the Alert System here
By Tim Hewison, EUMETSAT
Plans for GSICS products for GEO imagers for ISCCP-NG
Almost complete spectral coverage by IASI. RSB Spectral coverage of GEO images in 2022/2023.
DCC method applicable to VIS channels, lunar inter-calibration and Ray-matching may be applicable to all common channels in the Reflected Solar Band, but need further development.
Dave: Blended approach is very good as we are taking the best from several approaches ( DCC, Raymatching , LC)
Dave: The 3.8 micron channel is critical for cloud products - How can we monitor its calibration?
Tim: Current GEO-LEO IR algorithm only monitors these channels at night, but this should be followed up by GRWG.
Fangfang: For ABI did not see any difference between day and night.
Fangfang: Sometimes due to stray light it could induce anomalies in night
Tim: Seems to not be a problem with day/night but due to dynamic range.
Tim: It is a collective effort so no need for a task team.
Dave: If ISCCP-NG is going to meet twice a year, it is important to have a GSICS presentation in ISCCP-NG to get feedback from them.
Tim: Reciprocal attendance in GSICS meetings for ISCCP-NG is important too.
Ken: From outside the table summarising the maturity of the GSICS products for GEO imagers seems to show differences of quality.
Manik: Users are encouraged to use the products and provide feedback.
|pptx||Thoughts on ISCCP-NG GSICS.pptx||manage||34 K||12 Aug 2020 - 06:54||TimHewison|
|pptx||GSICS_ISCCPNG_WISHES.pptx||manage||1 MB||10 Aug 2020 - 06:26||TimHewison|
|pptx||feedback_discussion.pptx||manage||1 MB||13 Aug 2020 - 11:40||ManikBali||GSICS Response to ISSCP (Ken) feedback|
|pptx||Defining GSICS Deliverables for ISCCP-NG.pptx||manage||2 MB||12 Aug 2020 - 13:43||TimHewison|