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Periodic Reporting for period 1 - GAIA-CLIM (Gap Analysis for Integrated Atmospheric ECV CLImate Monitoring)


GAIA-CLIM will establish sound methods for the characterisation of satellite-based Earth Observation (EO) data by surface-based and sub-orbital measurement platforms.A critical component of the Copernicus framework is provision of high-quality observational datasets from...


GAIA-CLIM will establish sound methods for the characterisation of satellite-based Earth Observation (EO) data by surface-based and sub-orbital measurement platforms.

A critical component of the Copernicus framework is provision of high-quality observational datasets from satellites. These need to be calibrated and validated to standards that enable them to be used with confidence for applications. This requires ancillary datasets from in-situ and other sources of high-quality and sufficient quantity to robustly characterise sensor performance and radiative transfer modelling. The challenges to rigorous satellite data characterisation are formidable because without traceability in the comparator measures there is ambiguity in any comparison. The objective of GAIA-CLIM is to play a full role in supporting Copernicus by establishing prioritized needs for further observational capacity targeted at providing the required step-change in satellite calibration and validation capability. The consortium brings together scientific, technical and leadership expertise in high-quality in-situ and sub-orbital observations, gap analyses, modelling, satellite operations and data assimilation, and in setting the priorities for the EO community.

Robust EO instrument characterisation is about significantly more than simply where and when a given set of EO and ground-based / sub-orbital measurements is taken. It requires, in addition, quantified uncertainty estimation for the reference measurements and an understanding of additional uncertainties that accrue and increase the apparent discrepancy between measured data sets through mismatches in spatio-temporal sampling. It also needs user tools, which include statistical tools and the integrating capabilities afforded by data assimilation systems to enable users to access and work with the data in a ‘virtual observatory’ setting.

Work performed

Work carried out in the first 18 months (RP1) of GAIA-CLIM has included:

• An assessment report on a system of systems approach for assigning suitability of candidate non-satellite measurements for satellite calibration and validation, followed by its application to a broad range of candidate measurement networks and the collection of associated metadata.

• The construction of traceability chains for various non-satellite instrument types as a first step towards full instrument characterisation.

• Modelling and statistical based analysis describing generic metrology aspects of an atmospheric measurement and of data comparisons ( Verhoelst et al., 2015, AMT).

• A completed assessment of new satellite missions with respect to global NWP systems (GCOM-W AMSR-2, FY-3C and F-19 SSMIS) with the publication of Noh et al., 2016

• An initial version of the GRUAN processor which converts radiosonde profiles and their uncertainty to TOA radiance equivalent measurements, and subsequent preliminary software designed to monitor GRUAN data with respect to global NWP fields.

• Development of the Virtual Observatory (VO) based on user requirements derived from the user survey and the summary of the first user workshop with external users.

• Production of three official releases of a Gap Assessment Impact Document (GAID) which has become an online searchable catalogue of gaps and SMART remedies.

• Outreach activities related to GAIA-CLIM to date include:

o Participation at GCOS Road to the Future meeting to discuss current monitoring of ECVs and highlight new developments.

o Presentation at meeting on 183GHz measurement uncertainties and co-authorship on resulting paper (Brogniez et al. 2016)

o GAIA-CLIM-FIDUCEO interactions including planned coordination of 2017 General Assembly meetings with day at ECMWF discussing synergies and pull-through to Copernicus activities.

o GAIA-CLIM presented at the ESA Climate Modelling User Group (CMUG) meeting to highlight usability of project findings for ESA Climate Change Initiative (CCI) activities.

o Stand and associated outreach materials at European Space Solutions Conference

Various outreach materials have been produced and made available via the project website with numerous additional poster and oral presentations given by project participants at relevant meetings and fora.

• GAIA-CLIM project website ( produced with regular updates on:

o Progress on project activities per WP

o Deliverables and publications

o Outreach and dissemination material

o Dedicated page to GAID progress with regular updates, and ability for users to have access to a complete gap reference list for easy traceability, with a wiki link per gap.

Final results

To date GAIA-CLIM has made significant advances in the comprehensive geographical review of capabilities and gaps in the existing surface-based and sub-orbital observing systems for the characterization of EO measurement performance. Mapping and visualization of the existing capabilities based upon objective assessment criteria by ECV and by measurement fundamental characteristics has been undertaken. For these networks comprehensive discovery metadata has been collected and stored in a consistent format. The capabilities review and metadata are available online and shall be integrated into the Virtual Observatory.

An initial prototype of the GRUAN processor has been developed and subsequently used to monitor GRUAN data. This is a new and novel development enabling the transfer of the geophysical profile with uncertainty information to an equivalent TOA radiation measure and uncertainty. This enables future validation both of level1b and level 2 satellite products.

GAIA-CLIM is supporting the integration of scientific expertise on metrology and calibration of many of the principal global high-quality measurement groups and networks such as GRUAN, NDACC, TCCON, EARLINET and AERONET as well as EU funded projects such as QA4ECV, FIDUCEO and ConnectinGEO, substantially helping to improve cohesion and better understanding of areas of mutual concern and benefit.

More accurately characterized EO data would facilitate users understanding and ability to efficiently use EO networks. The final version of the GAID will support this requirement by identifying and assessing gaps in capabilities or knowledge against both existing and envisaged user requirements, as well as evaluating the scientific and societal impacts of the gaps. Realistic cost estimates and assessments of the risk / cost of leaving the gap unremedied will further advance the understanding on the impact of each gap and will support future prioritisation of gaps for informed decision making.

The improvement in EO instrument characterisation being undertaken will support the assessment of the accuracy of EO instruments and open opportunities for new global standards of accuracy and rigour of climate data records. This will greatly benefit the Copernicus Climate Change Services.

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