List of Figures

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Figure 1-1: Spatial distribution of the propagated SRS accuracies for 1982-2018 (left) and 2019-2020 06/2021 (right) years Figure 1-2: Spatial  Spatial distribution of the propagated SNS accuracies for 1982-2018 (left) and 2019-2020 06/2021 (right) years. There are gaps in the Arctic and Antarctic areas due to the difficulties in distinguishing between clouds and snow covered surfaces.

List of Tables

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title Click here to expand the list of figures
Table 2-1: Summary of validation results for SDL and SOL ICDR datasets (2019-202006/2021) Table 32-12: Summary of KPI results with 2.5 and 97.5 percentiles and number of ICDR months within the accuracy of the brokered CLARA-A2.1 data products, [D1] Section 1 for SIS, SOL, SDL TCDR, [D7] Section 1 for SIS ICDR. The accuracy estimation of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF Table 2-3: Summary of the accuracy of the extra data products Table 3 the rangeTable 4-1: Summary of the requirements and achieved accuracies achieved accuracy and stability of the brokered CLARA-A2.1 data products], Section 1 [D1 for SIS, SOL, SDL TCDR, D8 D7 for SIS ICDR]

General definitions

In the scope of the Copernicus Climate Change Service (C3S), two Surface Radiation Budget datasets are combined into one Climate Data Record (CDR) called "CLARA product family".

The first dataset, EUMETSAT's CM SAF CLARA-A2.1, is the core of this CDR. The second dataset includes extra data products that are not included in the CLARA-A2.1 dataset. The core data products are brokered from CM SAF. The extra net fluxes are not included in the brokered CLARA-A2.1 dataset and are calculated specifically within the C3S project as complimentary data for the convenience of users. Their format is as close as possible to the CLARA-A2.1 and the datasets are meant to be used together. Both datasets are frequently updated with Interim Climate Data Records (ICDRs) or simply extensions, generated using the same software and algorithms to cover more recent periods. The ICDR part for all products covers period from 2019 to 2020.

This separation into two datasets is necessary to keep the origin of the data, e.g. licence affiliations: "EUMETSAT's CM SAF" and "C3S", clear for individual products (Table 1)

Table 1: Licence overview of the CLARA product family Surface Radiation Products available through the CDS

Year

CDR Type

...

CLARA Product Family

...

SIS

...

SDL, SOL

...

SRS

...

Net Fluxes

...

 

...

Longwave fluxes

...

Extra data products

...

1982 – 2018

...

TCDR

...

CM SAF (CLARA-A2.1)

...

CM SAF

(CLARA-A2.1)

...

C3S

...

C3S

...

2019 – 2020

...

ICDR

...

CM SAF

(CLARA-A2.1 ICDR)

...

C3S

...

C3S

...

C3S

The longwave fluxes are not included in the CM SAF ICDR plans for the current phase. To ensure the dataset integrity and continuity, they are calculated within the C3S for the ICDR part. As such, the longwave fluxes change their licence affiliation, namely they are provided within the C3S project for the ICDR part (2019-2020) and are brokered from EUMETSAT’s CM SAF for the TCDR part (1982 to 2018).

Furthermore the CM SAF CLARA-A2.1 dataset has a temporal coverage of January 1982 to June 2019 (as described in [D2]), but TCDR data are only being brokered to the CDS up to December 2018. Data available from the CDS for January 2019 to December 2020 are brokered/derived from the CLARA A2.1 ICDR¹.

In contrast to the original CM SAF CLARA-A2.1 dataset, the brokered service within Copernicus solely provides:

• Level-3 data – excluding the level-2b data format.
• Data on a global equal angle grid – excluding the polar grid format.
• An aggregated version of all satellite data – excluding the provision of the individual satellite datasets.

...

icon	false

...

. The accuracy estimation of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF

General definitions

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table1 table1

Table 1: Summary of variables and definitions

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table2 table2

Table 2: Definition of satellite data provessing levels

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table3 table3

Table 3: Definition of special terms

Scope of the document

This document is the Product Quality Assessment Report (PQAR) for CLARA Product family CDR. This document provides validation results for the Climate Data Record (CDR) of the Surface Radiation Budget.

In the scope of the Copernicus Climate Change Service (C3S), two Surface Radiation Budget datasets are combined into one Climate Data Record (CDR) called “CLARA product family”.

The first dataset, EUMETSAT’s CM SAF CLARA-A2.1, is the core of this CDR. The second dataset, generated specifically within the C3S project, includes extra data products that are not included in the CLARA-A2.1 dataset. The core data products are brokered from CM SAF. The extra net fluxes are not included in the brokered CLARA-A2.1 dataset and are complimentary data provided for the convenience of users. Their format is as close as possible to the CLARA-A2.1 and the datasets are meant to be used together. Both datasets are frequently updated with Interim Climate Data Records (ICDRs) or simply extensions, generated using the same software and algorithms to cover more recent periods. The ICDR part for all products covers period from 2019 to 06/2021.

This separation into two datasets is necessary to keep the origin of the data, e.g. licence affiliations: “EUMETSAT’s CM SAF” and “Copernicus”, clear for individual products (Table 4).

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table4 table4

Table 4: Licence overview of the CLARA product family Surface Radiation Products, including products SIS, SDL, SOL, SRS and Net Fluxes. Products marked in blue are taken from the CLARA-A2.1 TCDR and the remaining products are Extra Data Products produced in the C3S project.

The longwave fluxes are not included in the CM SAF ICDR plans for the current phase. To ensure the dataset integrity and continuity, they are calculated within the C3S for the ICDR part. As such, the longwave fluxes change their licence affiliation, namely they are provided within the C3S project for the ICDR part (2019-06/2021) and are brokered from EUMETSAT’s CM SAF for the TCDR part (1982 to 2018).

Furthermore, the CM SAF CLARA-A2.1 dataset has a temporal coverage of January 1982 to June 2019 (as described in [D2]), but TCDR data are only being brokered to the CDS up to December 2018. Data available from the CDS for January 2019 to June 2021 are brokered/derived from the CLARA A2.1 ICDR¹.

In contrast to the original CM SAF CLARA-A2.1 dataset, the brokered service within Copernicus solely provides:

• Level-3 data – excluding the level-2b data format.

• Data on a global equal angle grid – excluding the polar grid format.

• An aggregated version of all satellite data – excluding the provision of the individual satellite datasets.

Info

1 The CM SAF CLARA-A2.1 and CLARA-A2.1 ICDR have a 6 month overlap from 01/2019 to 06/2019. One of the input datasets used in CLARA-A2.1, namely ERA-interim reanalysis data, is only available until August 2019 and dates after that are only covered by the newer ECMWF reanalysis version (ERA-5) and ECMWF IFS model. The CLARA-A2.1 ICDR uses ERA data from January 2019 onwards. The 6-month overlap between CLARA-A2.1 and CLARA-A2.1 ICDR is needed to ensure a sufficient period for data comparison and validation. CM SAF ATBD-ICDR contains more information on the overlap period [D8].

Executive summary

The brokering service of the CLARA-A2.1 data products includes 37 years (1982-2018) of level-3 data (monthly means) on a regular global latitude-longitude grid (with 0.25° x 0.25° resolution), merged from various polar orbiting satellites. It includes three products: the Surface Incoming Shortwave radiation (SIS), the Surface Outgoing Longwave radiation (SOL), and the Surface Downwelling Longwave radiation (SDL). SIS daily averages are also available within C3S.This CDR is brokered from EUMETSAT’s CM SAF. Therefore, this document only refers to the validation results from the original EUMETSAT CM SAF Validation Report [D1, D7]. It describes the validation methodology and the validation results.

The extra data products (produced specifically within the C3S project) are: the Surface Reflected Shortwave radiation (SRS), the Surface Net Shortwave radiation (SNS), the Surface Net Longwave radiation (SNL), and the Surface Radiation Budget (SRB). Validation results for these extra data products are described within this document. Validation results for SDL and SOL ICDR data products are described within this document.

An executive summary of the evaluation of the CLARA-A2.1 and CLARA-based ICDR surface radiation dataset can be found in CM SAF Validation Report, Section 1 [D1, D7].

The predefined requirements for accuracy of the SIS, the SOL and the SDL are given in CM SAF Product Requirement Document (PRD) [D2], Annex A. The achieved accuracies of CLARA-A2.1 correspond to the target accuracy requirements, only SIS daily accuracy corresponds to threshold accuracy. The validation methodology for the extra data products is selected in a way to provide the most conservative accuracy estimation, i.e. by assuming that the uncertainties in the input datasets align perfectly and contribute fully to the overall uncertainty. A summary of accuracy for CLARA-A2.1 and Extra data product is given in Table 5 and Table 6. Achieved accuracy and stability results allow consistent quantification of mean values, anomalies, variability and the Earth energy budget in general.

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table5 table5

Table 5: Summary of the accuracy of the brokered CLARA-A2.1 data products; [D1] Section 1 for SIS, SOL, SDL TCDR; [D7] Section 1 for SIS ICDR. The accuracy estimation of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF

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table6 table6

Table 6: Summary of the accuracy of the extra data products developed within the C3S.

1. Product validation methodology

In the scope of the Copernicus Climate Change Service (C3S), two Surface Radiation Budget datasets are combined into one Climate Data Record (CDR) called the “CLARA product family”.

1.1 Validation methodology for SIS, SOL, SDL

CLARA-A2.1 data products include the Surface Incoming Shortwave radiation (SIS), the Surface Outgoing Longwave radiation (SOL), and the Surface Downwelling Longwave radiation (SDL) datasets. These datasets were validated against reference data records from surface measurements obtained by the Baseline Surface Radiation Network (BSRN)². The reference dataset is described in detail in CM SAF Validation Report [D1], Section 4.

Therefore, this document refers to the original EUMETSAT CM SAF Validation Report [D1, D7]. It describes the validation methodology and the validation results. The accuracy estimation of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF.

The validation of the SIS ICDR (2019-06/2021) product is described in CM SAF Validation Report ICDR, Section 5.2 [D7]. The validation methodology of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF.

The validation methodology and definitions of the main metrics are provided in the C3S Product Quality Assurance Document (PQAD) [D4], Section 3, which refers to CM SAF Validation Report [D1], Section 5 and 5.1.

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2 Ohmura et al., 1998, Driemel et al., 2018

1.2 Validation methodology for CLARA family extra data products

The performed validation approach for extra data products is based on the method of error propagation. These data products arethe Surface Reflected Shortwave radiation (SRS), the Surface Net Shortwave radiation (SNS), the Surface Net Longwave radiation (SNL), and the Surface Radiation Budget (SRB).

The ICDR part data are validated in the same way as the TCDR.

1.2.1 Surface Reflected Shortwave Radiation (SRS)

The accuracy of the SRS is determined based on the accuracy of the Surface Incoming Shortwave Radiation (SIS) from the Surface Radiation Budget brokered from EUMETSAT’s CM SAF CLARA-A2.1 dataset [D1], and the Surface Albedo (SAL), not provided within the C3S.

The accuracy for the SRS is calculated using the fixed accuracy values for the SIS (ΔSIS = 10 W/m²) and the relative error of the SAL (ΔSAL = 25% of the SAL value). These values are the target requirements for accuracy from CM SAF Product Requirement Document [D2]. Resulting global mean accuracy for the SRS is 7.8 W/m² for TCDR and 6.6 W/m² for ICDR. Figure 1-1 illustrates the spatial distribution of the propagated SRS accuracies.

Image Added

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figure1_1 figure1_1

Figure 1-1: Spatial distribution of the propagated SRS accuracies for 1982-2018 (left) and 2019-06/2021 (right)

1.2.2 Surface Net Shortwave Radiation (SNS)

The accuracy of the SNS is determined based on the accuracy of the SIS and the SAL datasets. Estimations of the accuracy of the SIS product is given in CM SAF Validation Report [D1] and the accuracy of the SAL product is given in CM SAF Validation Report, Surface Albedo [D5].

The accuracy for the SRS is calculated using the fixed accuracy values for the SIS (ΔSIS = 10 W/m²) and the relative error of the SAL (ΔSAL = 25% of the SAL value). These values are the target requirements for accuracy from CM SAF Product Requirement Document [D2]. Resulting global mean accuracy for the SNS is 13.0 W/m² for TCDR and 12.0 W/m² for ICDR. Figure 1-2 illustrates the spatial distribution of the propagated SNS accuracies.

Image Added

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figure1_2 figure1_2

Figure 1-2: Spatial distribution of the propagated SNS accuracies for 1982-2018 (left) and 2019-06/2021 (right). There are gaps in the Arctic and Antarctic areas due to the difficulties in distinguishing between clouds and snow covered surfaces.

1.2.3 Surface Net Longwave Radiation (SNL)

The accuracy of the SNL is defined by the accuracy of the Surface Downwelling Longwave Radiation (SDL) and the Surface Outgoing Longwave Radiation (SOL), both datasets are the Surface Radiation Budget brokered from EUMETSAT’s CM SAF CLARA-A2.1 [D1].

Estimations of the accuracy of the SDL and the SOL products are given in CM SAF Validation Report [D1].

The accuracy for the SNL is calculated using the fixed accuracy values for the SDL (ΔSDL = 8.13 W/m²) and the SOL (ΔSOL = 13.77 W/m²). Resulting global mean accuracy for the SNL is 21.9 W/m². Global mean accuracy for the SNL ICDR is 17.1 W/m².

1.2.4 Surface Radiation Budget (SRB)

The accuracy of the SRB is defined by the accuracy of the SNS and the SNL datasets.

The accuracy for the SRB is calculated using the fixed accuracy values for the SNS (ΔSNS = 13.0 W/m² ) and the SNL (ΔSNL = 21.90 W/m² ). Resulting global mean accuracy for the SRB is 34.9 W/m². Global mean accuracy for the SNL ICDR is 29.1 W/m².

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validation validation

2. Validation results

2.1 Validation results for SIS, SOL, SDL

The TCDR (1982-2018) validation results are fully described in CM SAF Validation Report [D1], Section 5. The validation results for the SIS are provided in CM SAF Validation Report [D1], Section 5.2. The validation results for the SOL are provided in CM SAF Validation Report [D1], Section 5.3. The validation results for the SDL are provided in CM SAF Validation Report [D1], Section 5.4. Considerations for climate applications are provided in CM SAF Data Set Description [D3], Section 6. Conclusions for the validation results are provided in CM SAF Validation Report [D1], Section 6. Results are summarised in Table 2-2  in Section 2.2 below.

The validation results for SIS ICDR monthly and daily products are fully described in CM SAF Validation Report ICDR [D7], Section 5.2.

The validation results of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF. The summary of validation results for the monthly ICDR SDL and ICDR SOL datasets are shown in Table 2-1.

At the time of writing (May 2022) only 34 out of 60 BSRN stations have submitted data for years 2019-06/2021. 12 stations had less than 4 months worth of data and they were discarded. A full list of BSRN stations used in the validation and station-wise results are presented in Table 7 and Table 8, which can be found in the Appendix of this document. The outgoing longwave measurements are not carried out at all BSRN stations. Only 9 stations have submitted data for the years 2019-2021.

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table2_1 table2_1

Table 2-1: Summary of validation results for SDL and SOL ICDR datasets (2019-06/2021)

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section2_2 section2_2

2.2 Validation results for CLARA family extra data products (SRS, SNS, SNL, SRB)

The validation methodology for the extra data products is selected in a way to provide the most conservative accuracy estimation, i.e. by assuming that the uncertainties in the input datasets align perfectly and contribute fully to the overall uncertainty. Table 2-3 below provides a summary of the accuracies for the SRS, the SNS, the SNL, and the SRB.

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table2_2 table2_2

Table 2-2: Summary of the accuracy of the brokered CLARA-A2.1 data products, [D1] Section 1 for SIS, SOL, SDL TCDR, [D7] Section 1 for SIS ICDR. The accuracy estimation of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF

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table2_3 table2_3

Table 2-3: Summary of the accuracy of the extra data products

3. Application(s) specific assessments

A general overview of user requirements needed for climate monitoring is provided in CM SAF Product Requirements Document [D2]. There are three accuracy categories in the CM SAF PRD document ([D2], Section 5): threshold, target and optimal accuracies. They are defined keeping in mind different target users: operational climate monitoring, global and regional climate modelling and global and regional climate studies, respectively.

The Table 3-1 summarizes the achieved accuracy and stability for Surface Radiation Budget products, as well as the target requirements for accuracy and stability. The achieved accuracies correspond to the target accuracy requirements, only SIS daily accuracy corresponds to threshold accuracy.

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table3_1 table3_1

Table 3-1: Summary of achieved accuracy and stability of the brokered CLARA-A2.1 data products, Section 1 [D1 for SIS, SOL, SDL TCDR, D7 for SIS ICDR]. The accuracy estimation of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SA

Scope of the document

This document is the Product Quality Assessment Report (PQAR) for CLARA Product family CDR. This document provides validation results for the Climate Data Record (CDR) of the Surface Radiation Budget.

Executive summary

The brokering service of the CLARA-A2.1 data products includes 37 years (1982-2018) of level-3 data (monthly means) on a regular global latitude-longitude grid (with 0.25° x 0.25° resolution), merged from various polar orbiting satellites. It includes three products: the Surface Incoming Shortwave radiation (SIS), the Surface Outgoing Longwave radiation (SOL), and the Surface Downwelling Longwave radiation (SDL). SIS daily averages are also available within C3S. This CDR is brokered from EUMETSAT’s CM SAF. Therefore, this document refers to the original EUMETSAT CM SAF Validation Report [D1, D8]. It describes the validation methodology and the validation results.

The extra data products (produced specifically within the C3S project) are: the Surface Reflected Shortwave radiation (SRS), the Surface Net Shortwave radiation (SNS), the Surface Net Longwave radiation (SNL), and the Surface Radiation Budget (SRB). Validation results for these extra data products are described within this document.

The CLARA based ICDR data record is a continuation of the products of the CLARA-A2.1 and the extra data products. It extends both products by 2 years (2019-2020). The longwave fluxes are not included in the CM SAF ICDR plans for the current phase. Therefore SOL and SDL change their license affiliation, namely they are provided within the C3S project for the ICDR part (2019-2020) and are brokered from EUMETSAT’s CM SAF for the TCDR part (1982 to 2018). Table 1 provides an overview of the licenses for all data CLARA family products. Validation results for SDL and SOL ICDR data products are described within this document.

An executive summary of the evaluation of the CLARA-A2.1 and CLARA-based ICDR surface radiation dataset can be found in CM SAF Validation Report, Section 1 [D1, D8]

...

Product Name

...

Dataset accuracy [W/m²]

...

TCDR

...

ICDR

...

SIS monthly means

...

9.5

...

9.6

...

SIS daily means

...

18.6

...

22.9

...

SDL

...

8.1

...

15.8

...

SOL

...

13.8

...

9.2

...

Product Name

...

Propagated accuracy [W/m²]

...

TCDR

...

ICDR

...

SRS

...

7.8

...

6.5

...

SNS

...

13.0

...

14.2

...

SNL

...

21.9

...

25.0

...

SRB

...

34.9

...

39.2

1. Product validation methodology

In the scope of the Copernicus Climate Change Service (C3S), two Surface Radiation Budget datasets are combined into one Climate Data Record (CDR) called the "CLARA product family".

1.1 Validation methodology for SIS, SOL, SDL

CLARA-A2.1 data products include the Surface Incoming Shortwave radiation (SIS), the Surface Outgoing Longwave radiation (SOL), and the Surface Downwelling Longwave radiation (SDL) datasets. These datasets were validated against reference data records from surface measurements obtained by the Baseline Surface Radiation Network (BSRN, Ohmura et al., 1998, Driemel et al., 2018). The reference dataset is described in detail in CM SAF Validation Report [D1], Section 4.

Therefore, this document refers to the original EUMETSAT CM SAF Validation Report [D1, D8]. It describes the validation methodology and the validation results. The accuracy estimation of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF

The validation of the SIS ICDR (2019-2020) product is described in CM SAF Validation Report ICDR, Sections 5.2 [D8]. The validation methodology of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF.

The validation methodology and definitions of the main metrics are provided in the C3S Product Quality Assurance Document (PQAD) [D4], Section 3, which refers to CM SAF Validation Report [D1], Section 5 and 5.1.

1.2 Validation methodology for CLARA family extra data products

The performed validation approach for extra data products is based on the method of error propagation. These data products are the Surface Reflected Shortwave radiation (SRS), the Surface Net Shortwave radiation (SNS), the Surface Net Longwave radiation (SNL), and the Surface Radiation Budget (SRB).

The ICDR part data are validated in the same way as the TCDR

1.2.1 Surface Reflected Shortwave Radiation (SRS)

The accuracy of the SRS is determined based on the accuracy of the Surface Incoming Shortwave Radiation (SIS) from the Surface Radiation Budget brokered from EUMETSAT’s CM SAF CLARA-A2.1 dataset [D1], and the Surface Albedo (SAL), not provided within the C3S.

The accuracy for the SRS is calculated using the fixed accuracy values for the SIS ( ΔSIS = 10 W/m² ) and the relative error of the SAL ( ΔSAL = 25% of the SAL value). These values are the target requirements for accuracy from CM SAF Product Requirement Document [D2]. Resulting global mean accuracy for the SRS is 7.8 W/m² for TCDR and 6.5 W/m² for ICDR. Figures 1-1 and 1-2 provide the spatial distribution of the propagated SNS accuracies.

Image Removed

...

1.2.2 Surface Net Shortwave Radiation (SNS)

The accuracy of the SNS is determined based on the accuracy of the SIS and the SAL datasets.

Estimations of the accuracy of the SIS product is given in CM SAF Validation Report [D1] and the accuracy of the SAL product is given in CM SAF Validation Report, Surface Albedo [D6].

The accuracy for the SRS is calculated using the fixed accuracy values for the SIS ( ΔSIS = 10 W/m² ) and the relative error of the SAL ( ΔSAL = 25% of the SAL value). These values are the target requirements for accuracy from CM SAF Product Requirement Document [D2]. Resulting global mean accuracy for the SNS is 13.0 W/m². Figure 1-2 provides the spatial distribution of the propagated SNS accuracies.

Image Removed

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1.2.3 Surface Net Longwave Radiation (SNL)

The accuracy of the SNL is defined by the accuracy of the Surface Downwelling Longwave Radiation (SDL) and the Surface Outgoing Longwave Radiation (SOL), both datasets are the Surface Radiation Budget brokered from EUMETSAT’s CM SAF CLARA-A2.1 [D1].

Estimations of the accuracy of the SDL and the SOL products are given in CM SAF Validation Report [D1].

The accuracy for the SNL is calculated using the fixed accuracy values for the SDL ( ΔSDL = 8.13 W/m² ) and the SOL ( ΔSOL = 13.77 W/m²  ). Resulting global mean accuracy for the SNL is 21.9 W/m².

Global mean accuracy for the SNL ICDR is 25.0 W/m².

1.2.4 Surface Radiation Budget (SRB)

The accuracy of the SRB is defined by the accuracy of the SNS and the SNL datasets.

The accuracy for the SRB is calculated using the fixed accuracy values for the SNS ( ΔSNS = 13.0 W/m² ) and the SNL ( ΔSNL = 21.9 W/m² ).

Resulting global mean accuracy for the SRB is 34.9 W/m².

Global mean accuracy for the SNL ICDR is 39.2 W/m².

...

2.1 Validation results for SIS, SOL, SDL

The TCDR (1982-2018) validation results are fully described in CM SAF Validation Report [D1], Section 5. The validation results for the SIS are provided in CM SAF Validation Report [D1], Section 5.2 and 5.2. The validation results for the SOL are provided in CM SAF Validation Report [D1], Section 5.3. The validation results for the SDL are provided in CM SAF Validation Report [D1], Section 5.4. Considerations for climate applications are provided in CM SAF Data Set Description [D3], Section 6. Conclusions for the validation results are provided in CM SAF Validation Report [D1], Section 6.

Results are summarised in Table 1 in the Executive Summary.

The validation results for SIS ICDR monthly and daily are fully described in CM SAF Validation Report ICDR [D8], Section 5.2.

The validation results of SOL and SDL ICDR extensions is performed within the C3S using the algorithms developed by CM SAF. The summary of validation results for the monthly ICDR SDL and ICDR SOL datasets are shown in Table 2-1.

At the time of writing (May 2021) only 34 out of 60 BSRN stations have submitted data for years 2019-2020. 12 stations had less than 4 month worth of data and they were discarded. A full list of BSRN stations used in the validation and stationwise results are presented in Tables 6 and 7, Section 5  Appendix of this document. The outgoing longwave measurements are performed not on all BSRN stations. Only 9 stations have submitted data for years 2019-2020. A full list of BSRN stations used in the validation and stationwise results are presented in Table 6 and 7, Section 5 Appendix of this document.

...

Dataset

...

Number of months analysed

...

BSRB Stations

...

Abs.bias, W/m²

...

Std.Dev, W/m²

...

SDL, ICDR

...

404

...

24

...

15.8

...

25.16

...

SOL, ICDR

...

188

...

9

...

9.19

...

12.87

2.2 Validation results for CLARA family extra data products (SRS, SNS, SNL, SRB)

The validation methodology for the extra data products is selected in a way to provide the most conservative accuracy estimation, i.e. by assuming that the uncertainties in the input datasets align perfectly and contribute fully to the overall uncertainty. Table 2 in the Executive summary provides a summary of the accuracies for the SRS, the SNS, the SNL, and the SRB. The SRS accuracy is 7.8 (6.5) W/m², the SNS accuracy is 13.0 (14.2) W/m², the SNL accuracy is 21.9 (25.0) W/m², and the SRB accuracy is 34.9 (39.2) W/m², ICDR values are in parenthesis.

3. Application(s) specific assessments

In addition to the extensive product validation (see chapter 2 for results and chapter 2/3 in [D10] 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 [D9] 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.

...

p2.5 = 5.28 W/m²

p97.5 = 14.66 W/m²

...

30/30

...

p2.5 = 5.11 W/m²

p97.5 = 11.63 W/m²

...

29/30

...

p2.5 = 8.12 W/m²

p97.5 = 25.84 W/m²

...

30/30

...

p2.5 = 5.28 W/m²

p97.5 = 14.66 W/m²

...

36/36

...

p2.5 = 8.81 W/m²

p97.5 = 40.95 W/m²

...

36/36

...

p2.5 = 5.11 W/m²

p97.5 = 11.63 W/m²

...

35/36

...

p2.5 = 7.66 W/m²

p97.5 = 25.79 W/m²

...

35/36

...

p2.5 = 5.28 W/m²

p97.5 = 14.66 W/m²

...

41/42

...

p2.5 = 8.81 W/m²

p97.5 = 40.95 W/m²

...

42/42

...

p2.5 = 5.11 W/m²

p97.5 = 11.63 W/m²

...

42/42

...

p2.5 = 6.94W/m²

p97.5 = 25.72 W/m²

...

42/42

Percentiles were calculated based on the comparison of the TCDR using the Advanced Very High Resolution Radiometer (AVHRR) instrument against ground-based Baseline Surface Radiation Network (BSRN) measurements for the variables Surface Incoming Shortwave Radiation (monthly means and daily means), Surface Downwelling Longwave Radiation and Surface Outgoing Longwave Radiation from 1992-2018. All products stay within the TCDR-based limits and binomial tests lead to "good" KPI performance. The ICDR is therefore stable in relation to the deeply validated TCDR.

4. Compliance with user requirements

A general overview of user requirements needed for climate monitoring is provided in CM SAF Product Requirements Document [D2]. There are three accuracy categories in the CM SAF PRD document ([D2], Section 5): threshold, target and optimal accuracies. They are defined keeping in mind different target users: operational climate monitoring, global and regional climate modelling and global and regional climate studies, respectively.

Target requirement for accuracy (mean absolute error) are selected as follows:

• SIS monthly means: 10 Wm^-2 (corresponds to target accuracy),
• SIS daily means: 20 Wm^-2 (corresponds to threshold accuracy),
• SDL monthly means: 10 Wm^-2 (corresponds to target accuracy) and
• SOL monthly means: 10 Wm^-2 (corresponds to target accuracy).

Stability requirements for the Surface Radiation Budget TCDR are defined as follows:

...

At the time (~2010) when requirements for the CLARA-A2 data record had to be defined in [D2], there was no guidance available for surface radiation products in the available GCOS documents. Instead, requirements had to be set in a dialogue with experts and potential users (e.g., in association with CM SAF User Workshops).

New GCOS requirements for the ECV Surface Radiation Budget are summarized in GCOS-200 [

...

D6], Table 23, page 279 and include requirements for the horizontal resolution, temporal resolution, accuracy and stability. GCOS targets are:

• Frequency: Monthly (resolving diurnal cycle)

• Resolution: 100 km

• Measurement uncertainty: 1 Wm^-2 on global mean

• Stability: 0.2 Wm^-2dec^-1

However, these requirements are only valid for the net fluxes (i.e., SNS and SNL) and not for all individual radiation budget components. However, one could claim that individual radiation budget components should consequently be constrained in the same way as net fluxes.

All products in the brokered CLARA-A2.1 dataset fulfil the GCOS requirements regarding the horizontal and temporal resolution. However, the SNS

...

and SNL products do not fulfil the new GCOS requirements on accuracy and stability which are very stringent. Nevertheless, achieved accuracy and stability results allow consistent quantification of mean values, anomalies, variability and the Earth energy budget in general. We point out the existing uncertainties in the methodology of comparison with area-to point measurements (i.e. satellite-area to point-ground-based reference networks) as important reasons for not fulfilling the new requirements.

The compliance with the user requirements (as defined in the CM SAF PRD document ([D2], Section 5) for the SIS, SDL, and SOL is provided in Table 10 above.

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references references

References

Driemel, A., et al. (2018). Baseline Surface Radiation Network (BSRN): structure and data description (1992--2017). Earth System Science Data, 10(3), pp. 1491--1501. doi:10.5194/essd-10-1491-2018

Ohmura, A., et al. (1998). Baseline Surface Radiation Network (BSRN/WCRP): New precision radiometry for climate research. Bulletin of the American Meteorological Society, 79(10), pp. 2115-2136

Further references are listed in CM SAF Validation Report [D1], Section 7.

Appendix

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table7 table7

Table 7: Station-wise validation results for SDL, 2019-06/2021

The compliance with the user requirements (as defined in the CM SAF PRD document ([D2], Section 5) for the SIS, SDL, and SOL is provided in Table 4-1.

...

Product Name

...

Threshold/ Target / Optimal accuracies

...

Dataset accuracy [W/m²]

...

TCDR

...

ICDR

...

SIS monthly means

...

15 / 10 / 8

...

9.5

...

9.6

...

SIS daily means

...

30 / 20 / 15

...

18.6

...

22.9

...

SDL

...

15 / 10 / 8

...

8.1

...

15.8

...

SOL

...

15 / 10 / 8

...

13.77

...

9.2

The validation methodology for the extra data products is selected in a way to provide the most conservative accuracy estimation, i.e. by assuming that the uncertainties in the input datasets align perfectly and contribute fully to the overall uncertainty. The SRS accuracy is 7.8 (6.5) W/m², the SNS accuracy is 13.0 (14.2) W/m², the SNL accuracy is 21.9 (25.0) W/m², and the SRB accuracy is 34.9 (39.2) W/m², ICDR values are in parenthesis.

Appendix

...

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table7table8table7 table8

Table 78: Stationwise Station-wise validation results for SOL, 2019-202006/2021

References

Ohmura, A., et al. (1998), Baseline Surface Radiation Network (BSRN/WCRP): New precision radiometry for climate research, Bulletin of the American Meteorological Society, 79(10), 2115-2136.

Driemel, A., et al. (2018): Baseline Surface Radiation Network (BSRN): structure and data description (1992-2017), Earth System Science Data, 10(3), 1491-1501, doi:10.5194/essd-10-1491-2018.

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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), operated by the European Centre for Medium-Range Weather Forecasts on behalf on the European Union (Contribution Agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee 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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