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Contributors: E. Carboni (UKRI-STFC RAL Space), G.E. Thomas (UKRI-STFC RAL Space)produced in

Issued by: STFC RAL Space (UKRI-STFC) / Elisa Carboni

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Reference ID Document D1 Product Validation and Intercomparison Report (PVIR), v6.1. ESA Cloud_cci. https://climate.esa.int/media/documents/Cloud_Product-Validation-and-Intercomparison-Report-PVIR_v6.0.pdf Last accessed on 28/02/2023 D2 Karlsson, K.-G., et al., (2023) C3S Earth Radiation Budget CDRs releases until 2021: Target Requirements and Gap Analysis Document. Copernicus Climate Change Service. Document ref. C3S2_D312a_Lot1.3.1.1-2021_TRGAD-ERB_v1.1 ERB: Target Requirements and Gap Analysis Document Last accessed on 31/05/2023 D3 Thomas, G. (2023) C3S Earth Radiation Budget Service: Algorithm Theoretical Basis Document. Copernicus Climate Change Service, Document ref C3S2_D312a_Lot1.2.2.2-v4.0_202305_ATBD_CCIEarthRadiationBudget_v1.2 ERB CCI-ICDR: Algorithm Theoretical Basis Document (ATBD) Last accessed on 31/05/2023

Acronyms

D4 Meirink, J.F., et al, (2023) C3S cross ECV document Service: Key Performance Indicators (KPIs). Copernicus Climate Change Service, Document ref. C3S2_D312a_Lot1.3.7.1_202303_Unified_KPI_Approach_v1.0 Key Performance Indicators (KPIs) Last accessed: 23.08.2023 D5 Carboni, E., Thomas, G. (2022) C3S Earth Radiation Budget Service: Product Quality Assurance Document. Copernicus Climate Change Service, Document ref. C3S2_D312a_Lot1.1.2.3-v4.0_202301_PQAD_CCIEarthRadiationBudget_v1.1 ERB CCI ICDR: Product Quality Assurance Document Last accessed on 31/05/2023

Acronyms

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Acronym Definition AATSR Advanced Along-Track Scanning Radiometer ATBD Algorithm Theoretical Basis Document ATSR Along-Track Scanning Radiometer C3S Copernicus Climate Change Service CCI Climate Change Initiative CDR Climate Data Record CERES Clouds and Earth Radiation Energy System ENVISAT Environmental
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Acronym Definition AATSR Advanced Along-Track Scanning Radiometer ATBD Algorithm Theoretical Basis Document ATSR Along-Track Scanning Radiometer C3S Copernicus Climate Change Service CCI Climate Change Initiative CDR Climate Data Record CERES Clouds and Earth Radiation Energy System ENVISAT Environmental Satellite ERS European Research Satellite ESA European Space Agency ICDR Interim CDR OLR Outgoing Longwave Radiation RAL Rutherford Appleton Laboratory RSF Reflected Solar radiation Flux SLSTR Sea and Land Surface Temperature Radiometers STFC Science and Technology Facilities Council TCDR Thematic Climate Data Record TOA Top Of the Atmosphere

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Table 2-1: Summary of the TCDR and preliminary assessment of ICDR accuracy of the Earth Radiation Budget dataset. Table 43-1: Summary of KPI results with 2.5 and 97.5 percentiles and number of ICDR months within the range Table 4-1: GCOS targets for Earth Radiation GCOS targets for Earth Radiation Budget ECVs and CDR values.

List of figures

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Figure 2-1: RSF and OLR from SLSTR (ICDR dataset) for March 2017. Figure 2-2: RSF and OLR from CERES dataset for March 2017.

General definitions

The "CCI product family" Climate Data Record (CDR) consists of two parts. The ATSR2-AATSR Earth Radiation Budget CDR is formed by a TCDR brokered from the ESA Cloud_cci project and an ICDR derived from the Sea and Land Surface Temperature Radiometer (SLSTR) on board of Sentinel-3A and -B. ICDR uses the same processing and infrastructure as the TCDR. Both TCDR and ICDR data have been produced by STFC RAL Space.

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Table 1: Definition of processing levels

Table 2: Definition of various technical terms used in the document

Scope of the document

This document provides a description of the product validation results for the Climate Data record (CDR) of the Essential Climate Variable (ECV) Earth Radiation Budget. This CDR comprises inputs from two sources: (i) brokered products from the Cloud Climate Change Initiative (ESA's Cloud_cci), namely those coming from processing of the Advanced Along-Track Scanning Radiometer ((A)ATSR) data and (ii) those produced under this contract for the Climate Data Store, specifically those coming from processing of the Sea and Land Surface Temperature Radiometers (SLSTR).

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1 Data available here: https://ceres.larc.nasa.gov/data/ (Last accessed on 28/02/2023).

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2. Validation results

The validation results for the TCDR are provided in [D1] section 3 and 5. Table 2-1 provides a summary of the resulting TCDR accuracies.

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table2_1 table2_1

Table 2-1: Summary of the TCDR and preliminary assessment of ICDR accuracy of the Earth Radiation Budget dataset.

2.1 TCDR validation with CERES satellite data

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Figure 2-1: RSF and OLR from SLSTR (ICDR dataset) for March 2017.

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Figure 2-2: RSF and OLR from CERES dataset for March 2017.

3. Application(s) specific assessmentsassessments

In addition to the extensive product validation (see chapter 2 for results and chapter 2/3 in [D5] for validation methodology) a second assessment is introduced to evaluate the Interim Climate Data Record (ICDR) against the Thematic Climate Data Record (TCDR) in terms of consistency. Since frequent ICDR deliveries make detailed validation not feasible, a consistency check against the deeply validated TCDR is used as an indication of quality. This is done by a comparison of the following two evaluations:

• TCDR against a stable, long-term and independent reference dataset
• ICDR against the same stable, long-term and independent reference dataset

The evaluation method is generated to detect differences in the ICDR performance in a quantitative, binary way with so called Key Performance Indicators. The general method is outlined in [D4] chapter 3. The same difference between TCDR/ICDR and the reference dataset would lead to the conclusion that TCDR and ICDR have the same quality (key performance is "good"). Variations or trends in the differences (TCDR/ICDR against reference) would require a further investigation to analyze the reasons. The key performance would be marked as "bad". The binary decision whether the key performance is good or bad is made in a statistical way by a hypotheses test (binomial test). Based on the TCDR/reference comparison (global means, monthly or daily means) a range is defined with 95% of the differences are within. This range (2.5 and 97.5 percentile) is used for the ICDR/reference comparison to check whether the values are in or out of the range. The results could be the following:

• All or a sufficient high number of ICDR/reference differences lies within the range defined by the TCDR/reference comparison: Key performance of the ICDR is "good"
• A smaller number of ICDR/reference differences is within the pre-defined range: Key performance of the ICDR is "bad"

3.1 Results

The results of the KPI test are summarized in Table 3-1.

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table3_1 table3_1

Table 3-1: Summary of KPI results with 2.5 and 97.5 percentiles and number of ICDR months within the range. Colors green or red mark the results of the binomial tests as good or bad, respectively.

Percentiles were calculated based on the comparison of the TCDR using the Advanced Along Track Scanning Radiometer (AATSR) instrument against CERES as reference dataset for the variables Outgoing Longwave Radiation (OLR) and Reflected Shortwave Flux (RSF). Percentiles were based on the time from 2002-2012 with monthly means and applied to the ICDR from 01/2017 (10/2018) to 06/2022 for Sentinel-3A (Sentinel-3B and merged product Sentinel-3A+B) based on measurements of the Sea and Land Surface Temperature Radiometer (SLSTR).

A part of the ICDR months are outside the TCDR-based KPI limits and leading to “bad” KPI tests. For these, the ICDR is not stable in relation to the TCDR. This is due to multiple reasons starting with the fact of a five year gap (2012-2016) between TCDR and ICDR. In addition, TCDR and ICDR are based on different instruments with SLSTR on Sentinel-3 and (A)ATSR/ATSR-2 on Envisat/ERS-2, respectively. Differences occur due to a lower bias between ICDR and reference dataset and a subtraction of the monthly means (based on the TCDR) to remove the annual cycle leads to values outside of the KPI range (see method in [D4], chapter 3.2.2). Please note that significant changes between 01/2017 - 12/2020 and 01/2017 - 12/2021 are due to bugfixesThis section is not applicable. There are no additional specific assessments known since the dataset has just been published.

4. Compliance with user requirements

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table4_1 table4_1

Table 4-1: GCOS targets for Earth Radiation Budget ECVs and CDR values.

Known limitations [From D1 table 7.1]:

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Loeb, N.G., Doelling, D.R., Wang, H., Su, W., Nguyen, C., Corbett, J.G., Liang, L., Mitrescu, C., Rose, F.G., and Kato, S.: Clouds and the Earth's Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Top-of-Atmosphere (TOA) Edition 4.0 Data Product, J.Climate, 31(2), 895–918, doi:10.1175/JCLI-D-17-0208.1, 2018.

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This document has been produced with funding by the European Union in the context of the Copernicus Climate Change Service (C3S) .The activities leading to these results have been contracted , operated by the European Centre for Medium-Range Weather Forecasts , operator of C3S on behalf of on the European Union ( Delegation Agreement signed on 11/11/2014 and Contribution Agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee or of warranty is given that the information is fit for any particular purpose. The users thereof use the information at their sole risk and liability. For the avoidance of all doubt, the European Commission and the European Centre for Medium-Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view.

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