1. Atmospheric Composition Virtual Constellation (AC-VC)
Jay Al-Saadi (NASA) & Ben Veihelmann (ESA), AC-VC co-chairs
Dave Crisp (CalTech/NASA JPL), AC-VC GHG lead
CEOS 2019 SIT Technical Workshop
Session 5 Agenda Item 5.1
Fairbanks, Alaska, USA
11 – 12 September 2019

2. Linkages to CEOS Work Plan
Contribute to CMRS-25, implementation of GHG monitoring system
Led by WGClimate
Prototype atmospheric inventory requirements [2020]
Prototype inventory [2021]
Requirements for an Operational GHG System [2023 ]
VC-2, Ozone dataset validation and harmonization [Q4 2020]
Peer-reviewed papers on intercomparisons of satellite total column ozone
VC-3, Air Quality (AQ) Constellation Coordination [Q1 2019]
Document on validation needs for the AQ Constellation presented for final review 6/2019 during AC-VC-15
Proposing new deliverable, Aerosol Air Quality [Notionally Q4 2021]

3. The CEOS Architecture for Monitoring Atmospheric CO2 and CH4 Concentrations
The CEOS Atmospheric Composition Virtual Constellation (AC-VC) white paper defines a global architecture for monitoring atmospheric CO2 and CH4 concentrations from instruments on space-based platforms
166-page document, 88 authors from 47 organizations
Executive Summary (2 pages)
Body of report (75 pages)
Technical Appendices (42 pages)

4. GHG Whitepaper Publication
Project Number:
Title: EUR A constellation architecture for monitoring carbon dioxide and methane from space
Linguistic version
Media/Volume
Catalogue number
ISBN
ISSN
DOI
EN BOOK
PRINTED/Volume_01
KJ-NA EN-C
/888266
EN PDF
PDF/Volume_01
KJ-NA EN-N
/468219
* The ISSN remains valid as long as the title of the serial remains unchanged. Please inform us of any title changes and/or the cessation of publication.

5. GHG Roadmap: AC-VC Roles*
Coordinate ongoing agency activities to implement a prototype atmospheric GHG inventory system that incorporates products from a virtual constellation of sensors by 2021 (Rec#1)
Define a dedicated operational constellations of sensors for GHGs as part of the backbone for the Climate Monitoring Architecture (Rec#2)
Track implementation and operations of space-based GHG sensors (Rec#14)
Facilitate exchange of expertise and support in defining mission requirements (Rec#7)
Work with WGCV ACSG and GSICS to define best practices and facilitate exchange and harmonization of approaches for instrument cross-calibration (Rec#10)
Coordinate efforts to perform OSSEs to support trade studies on constellation architecture (Rec#8)
Coordinate discussion on auxiliary observations enhancing data quality (e.g., aerosol properties for light path correction) (Rec#15)
Discuss possible role of an active mission as flying standard in a GHG constellation (Rec#14)
Coordinate the development of a more complete atmospheric GHG inventory for the 2028 Stocktake
Work with WGClimate to identify and propose solutions for observational gaps (Rec#14) * *
New Activities Ongoing Activities *Primary Action (i.e. Deliverable)

6. VC-02 Ozone Data Validation/Harmonization
The total ozone part of CEOS VC-02 is now completed
Submitted peer-reviewed papers on inter- comparisons of satellite total column ozone
Total ozone ECV products will continue to be produced operationally
We now propose a new target deliverable for tropospheric ozone column products
Relevant; contributes to UN SDGs 3 (health and air quality), 2 (agricultural production), 13 (short lived climate pollutants)
Needs maturation; several existing (and relatively new) satellite techniques (UV, IR, combinations) and products, but large differences exist
Notional target deliverable would be a rigorous intercomparison exercise followed by peer- reviewed journal article [by Q4 2022]
Procedurally, accomplish via extending VC-02 or closing VC-02 and opening new deliverable

7. Graphic: NASA LaRC NO2 Image: KNMI/ESA
VC-03 Air Quality (AQ) Constellation Coordination
Graphic: NASA LaRC NO2 Image: KNMI/ESA

8. VC-03: Purpose of ‘Geo-AQ Validation Needs’ Whitepaper
Elaborate the validation needs of the Geo-AQ Constellation: focus on
New challenges for geostationary atmospheric composition missions (new wrt LEO heritage)
Enhancing the success of the missions when seen as element of a constellation
Identify ‘Constellation Products’
Common to the Geo-AQ missions
Enhanced value by establishing and monitoring inter-mission consistency
Set quantitative inter-mission consistency targets for the Constellation Products
Taking into account individual product performances and the accuracy of validation methods
Identify activities needed to assess and establish this consistency
Activities to be performed consistently for each mission
Activities addressing new Geo-AQ challenges and inter-mission consistency
Coordination and continuity
Make specific and actionable recommendations

9. VC-03 Air Quality (AQ) Constellation Coordination
“Validation needs for the AQ Constellation” white paper final review 6/2019 (AC-VC-15)
Minor comments have been incorporated
Recommendations:
Consistently perform intensive campaigns dedicated to the validation of the capability of the Geo-AQ missions to observe the diurnal cycle of the target species (several supersites within each Geo-AQ mission domain).
Conduct joint validation campaigns with exchange of reference airborne and ground-based instruments.
Further develop and eventually apply approaches to the radiometric inter-calibration of the Geo-AQ missions. These activities should be pursued within the frame of the WMO GSICS initiative.
Further develop and eventually apply approaches to the inter-calibration of the Level-2 products of the Geo-AQ missions.
Systematically process the Level-2 Constellation Products of the Geo-AQ missions, using one selected common algorithm per Constellation Product.
Further pursue the harmonization of the reference data used for validation and inter-mission consistency verification of Level-2 products.
Implement a data centre for storage and exchange of all validation data collected for the Geo-AQ missions, accessible to the entire community involved in the validation of the Geo-AQ mission products, very soon after acquisition.
Implement a coordinating unit for ensuring the consistency of the approach and the metrics used for validating the Geo- AQ mission products and their inter-mission consistency.

10. VC-03 Air Quality (AQ) Constellation Coordination
AC-VC now ready to submit the white paper for endorsement (or acceptance as appropriate) by CEOS plenary and proceed with implementation of the recommendations
Can close VC-03 and open specific new deliverables as needed, or extend VC-03 with specific annual targets
Some recommendations are best practices that each mission is encouraged to pursue consistently
Mission teams implement; no additional resource requests of CEOS agencies, but benefit from ongoing CEOS interaction and coordination
Recommendations 1, 3, 4, 6
Implementation of other recommendations may require resource commitments from CEOS member agencies
Recommendations 2, 5, 7, 8
Some of these commitments are already being discussed individually among member agencies

11. Proposed new deliverable: Aerosol Air Quality
AC-VC would now like to propose a new deliverable on satellite-informed products for air quality associated with aerosol
Motivated by SDG 3.4 human health mortality goal and Global Burden of Disease report
What can space agencies and partners do to better enable progress in measuring and monitoring?
Novel; aerosol observation coordination efforts so far have focused on climate (radiative) effects whereas AQ needs to know near-surface, size-resolved, speciated mass concentration
Focus on capabilities of existing/planned satellite instruments and other assets, then make specific recommendations on investment opportunities
Express known (i.e. funded) activities, possibly using them to help identify gaps
Stimulate the exploitation of synergies of combining different observational techniques (e.g., LEO-GEO, passive-active, multispectral, multiangle, polarimetric) with model calculations
Define best practices for combining particulate pollution information from satellites and other sources; satellite observations alone are insufficient
Envisioned focus on advocacy of new products and techniques rather than new missions
Notional target deliverable is a white paper or peer-reviewed journal article [by Q4 2021]

12. Summary Deliverables are on schedule Requests of Plenary
Contribute to CMRS-25, implementation of GHG monitoring system, pending resource discussions
VC-02, Ozone dataset validation and harmonization
VC-03, Air Quality (AQ) Constellation Coordination
Requests of Plenary
Endorse/accept the VC-03 white paper on Geophysical Validation Needs for the Geostationary Satellite Constellation
Requests of SIT and Executive leadership for the next work plan
Evolve VC-02 Deliverable to new focus on Tropospheric Ozone
Evolve VC-03 Deliverable to implementation
Open new Deliverable for Aerosol Air Quality

13. Questions?