Quality Assurance for Earth Observation(QA4EO) concept and example
J.-C. Lambert, S. Compernolle, D. Hubert, A. Keppens, and T. Verhoelst
Royal Belgian Institute for Space Aeronomy (BIRA-IASB)

2nd ESA EarthCARE Validation Workshop
25-28 May 2021 (online)

ESA UNCLASSIFIED – For ESA Official Use Only1

Quality Assurance for Earth Observation (QA4EO)
concept and example
1. QA4EO framework
2. QA4EO implementation methods and tools
3. Example 1: QA4ECV QA system applied tomulti-mission NO2 Climate Data Record
4. Example 2: Validation of Sentinel-5p NO2
intermediate retrieval parameters2

2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

J.-C. Lambert et al.

QA4EO Concept and Example

LEO+GEO Satellite Constellation for Air Quality
2024-2038
2022-2029
2020-2031

2017-2024
2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

2023-2044

2011-2038
J.-C. Lambert et al.

2018-2026

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QA4EO Concept and Example

http://qa4eo.org

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2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

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4QA4EO Concept and Example

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2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

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QA4EO Concept and Example

CEOS WGISS Data Management & Stewardship Maturity Matrix
Usability criteria: encoding, documentation, traceability, validation, data uncertainty, QA/QC

notmanaged

https://ceos.org

fullymanaged6

2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

J.-C. Lambert et al.

QA4EO Concept and Example

Generic validation chain, state-of-the-art co-locators,
harmonized terminology, common metrics…

Cross GEOSSEO Cal/Val
harmonization
WGCV-28/…/31 initiatives

cciozone

ACC-8/…/11

Communityfeedback &endorsement
Implementation inFP7 QA4ECV,H2020 GAIA-CLIM,C3S Ozone, HARP,
Sentinel-5p MPC,
CAMS-NDACC,
7CCI+, CCVS…

Lambert et al., ISSI 2012
Keppens et al., AMT 2015
Verhoelst et al., AMT 2015, EC TN 2016
Hubert et al., AMT 2016
Compernolle et al., EC TN 2016, 2017
Keppens et al., AMT 2019
Verhoelst et al., AMT 2021
Compernolle et al., ACP 2019, AMT 2020
2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

Prototyping in
Multi-TASTE andESA CCI_Ozone

J.-C. Lambert et al.

QA4EO Concept and Example

Generic round-robin validation protocol → set of Quality Indicators

m1 - m 2 < k s2 + u12 + u 22
8Keppens et al., AMT 2015
2nd EarthCARE Validation Workshop (online)- 25-28 May 2021

J.-C. Lambert et al.

QA4EO Concept and Example

Validation practices across EO domains• Objectives of Cal/Val• Terminology• Mathematicalformulation• Validation metrics• Advanced methods
and strategies

9Loew et al., Rev. Geophys. 2017
2nd EarthCARE Validation Workshop (online)- 25-28 May 2021

J.-C. Lambert et al.

QA4EO Concept and Example

Quality Assurance system for EO ECVs•

FP7 project 2014-2018•

QA4EO implementation
for ECVs•Applied to 6 pilot ECVs:

http://www.qa4ecv.eu

Land•

surface spectral albedo•FAPAR•

LAIAtmosphere•

NO2•HCHO•

CO10

2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

J.-C. Lambert et al.

QA4EO Concept and Example

QA4ECV QA system for EO ECVs: atmospheric NO2
First cross-calibrated, multi-sensor
NO2 Climate Data Record, spanning20+ years, with very detailed quality
information embedded.

1995-2003

2002-2012

2004- ?

2006-2021

2012- ?

11Boersma et al., AMT 2018
2nd EarthCARE Validation Workshop (online)- 25-28 May 2021J.-C. Lambert et al.

QA4EO Concept and Example

QA4ECV QA system for EO ECVs: atmospheric NO2
Nightingale et al. – QA4ECV QA System

Further work (inspired among others by outcome of QA4ECV audits):•

Improved retrieval method•

L1 calibration and L2 retrieval•

Tailoring of ground-based validation measurements (FRM)•Validation of NO2 intermediate and influence quantities•

Uncertainty assessment, representativeness2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

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QA4EO Concept and Example

Advances in NO2 validation

Multi-network validation of Sentinel-5p TROPOMI NO2 intermediate quantities
Stratospheric: vs. zenith-sky DOAS

Tropospheric: vs. multi-axis DOAS

Total: vs. direct sun DOAS

Up to v1.3
From v1.4

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Verhoelst et al., AMT 2021
2nd EarthCARE Validation Workshop (online)- 25-28 May 2021

J.-C. Lambert et al.

QA4EO Concept and Example

Advances in NO2 validation

Validation of Sentinel-5p TROPOMI cloud properties
as influence quantities for trace gas retrievals

14Compernolle et al., AMT 2020
2nd EarthCARE Validation Workshop (online)- 25-28 May 2021

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QA4EO Concept and Example

Conclusion• QA4EO provides a set of guidelines facilitating the data quality
assurance of EO missions, enhancing their value, completeness,interoperability, and heritage.
• Application and value of QA4EO demonstrated for several atmospheric
EO data products and several cross-domain EO based services• Maturity of QA4EO implementation depends on geophysical variable,
data retrieval scheme, community, user needs…
• Highlights further research needs: expression and calculation of data
uncertainties, representativeness issues, interoperability requirements,
new validation approaches…
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2nd EarthCARE Validation Workshop (online) - 25-28 May 2021

J.-C. Lambert et al.

QA4EO Concept and Example