Jay Al-Saadi (NASA) & Ben Veihelmann (ESA), AC-VC co-chairs

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. 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] Linkages to CEOS Work Plan

3. The CEOS Architecture for Monitoring Atmospheric CO2 and CH4 Concentrations http://ceos.org/document_management/Virtual_Constellations/ACC/Documents/CEOS_AC-VC_GHG_White_Paper_Publication_Draft2_20181111.pdf 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

5. GHG Roadmap: AC-VC Roles * * * New ActivitiesOngoing Activities *Primary Action (i.e. Deliverable) • 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)

6. 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 tobe 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 VC-02 Ozone Data Validation/Harmonization

7. Graphic: NASA LaRCNO2 Image: KNMI/ESA VC-03 Air Quality (AQ) Constellation Coordination

8. 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 VC-03: Purpose of ‘Geo-AQ Validation Needs’ Whitepaper

9. “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. VC-03 Air Quality (AQ) Constellation Coordination

10. 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 VC-03 Air Quality (AQ) Constellation Coordination

11. 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] • Proposed new deliverable: Aerosol Air Quality

12. Deliverables are on schedule • 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 • Summary

13. Questions?