Page info infoType Modified date prefix Last modified on type Flat
Contributors: G.E. Thomas (UKRI-STFC RAL Space), R.Shevchuk (Brockmann Consult)
Issued by: STFC RAL Space (UKRI-STFC) / Gareth Thomas and Brockmann Consult / Roman Shevchuk
Date: 0629/0307/20232024
Ref: C3S2_D312a_Lot1.2.3.4-v4.0_2023036_202407_PUGS_ECV_SRB_CCISurfaceRadiationBudgetSLSTR_v1.12
Official reference number service contract: 2021/C3S2_312a_Lot1_DWD/SC1
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List of datasets covered by this document
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Acronyms
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Acronym
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Definition
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AATSR
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Advanced Along-Track Scanning Radiometer
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(A)ATSR
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Shorthand for the Along-Track Scanning Radiometer series of instruments. In the current context, refers to ATSR-2 and AATSR.
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ATBD
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Algorithm Theoretical Basis Document
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ATSR-1, -2
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Along Track Scanning Radiometer
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AVHRR
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Advanced Very High Resolution Radiometer
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BRFR
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Broadband Radiative Flux Retrieval
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C3S
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Copernicus Climate Change Service
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CAMS
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Copernicus Atmosphere Monitoring Service
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CC4CL
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Community Cloud for Climate
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CCI
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(ESA) Climate Change Initiative
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CDR
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Climate Data Record
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CDS
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Climate Data Store
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DARD
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Data Access Requirements Document
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ECV
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Essential Climate Variable
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ENVISAT
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(the) Environmental Satellite
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ERB
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Earth Radiation Budget
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ERS-2
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Environmental Research Satellite
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ESA
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European Space Agency
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FCDR
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Fundamental Climate Data Record
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GCOS
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Global Climate Observing System
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ICDR
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Interim Climate Data Record
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IR
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InfraRed
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MODIS
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Moderate Resolution Imaging Spectroradiometer
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NIR
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Near InfraRed
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ORAC
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Optimal Retrieval of Aerosol and Cloud
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PUGS
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Product User Guide and Specification
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RAL
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Rutherford Appleton Laboratory
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SLSTR
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Sea and Land Surface Temperature Radiometer
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STFC
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Science and Technology Facilities Council
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TCDR
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Thematic Climate Data Record
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UKRI
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UK Research and Innovation
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WMO
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World Meteorological Organization
List of tables
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Table 1-1: GCOS targets for Surface Radiation Budget ECVs Table 1-2: Surface Radiation Budget variables included in Cloud_cci TCDR and SLSTR ICDR monthly products. |
List of figures
General definitions
Table 1: Summary of variables and definitions
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Variables
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Abbreviation
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Definition
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Surface incoming solar radiation
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SIS
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Total incoming shortwave (UV, visible, near-IR) radiation, measured at the Earth’s surface.
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Surface reflected solar radiation
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SRS
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Total upwelling shortwave radiation, measured at the Earth’s surface.
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Surface net solar radiation
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SNS
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The net shortwave radiation, measured at the Earth’s surface. Equal to the difference between SIS and SRS.
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Surface downwelling longwave radiation
SDL
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Total downwelling thermal radiation, measured at the Earth’s surface.
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Surface outgoing longwave radiation
SOL
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Total upwelling thermal radiation, measured at the Earth’s surface.
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Surface net longwave radiation
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SNL
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The net longwave radiation, measured at the Earth’s surface. Equal to the difference between SDL and SOL.
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Surface radiation budget
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SRB
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The total net radiative flux (both short- and longwave) at the Earth’s surface. Equal to the total of SNS and SNL.
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Acronyms
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List of tables
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Table 1-1: GCOS targets for Surface Radiation Budget ECVs Table 1-2: Surface Radiation Budget variables included in Cloud_cci TCDR and SLSTR ICDR monthly products. |
List of figures
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Figure 1-1: Overview of data producers, satellites, time coverages and grids for the ICDRs. |
General definitions
Table 1: Summary of variables and definitions
Variables | Abbreviation | Definition |
Surface incoming solar radiation | SIS | Total incoming shortwave (UV, visible, near-IR) radiation, measured at the Earth’s surface. |
Surface reflected solar radiation | SRS | Total upwelling shortwave radiation, measured at the Earth’s surface. |
Surface net solar radiation | SNS | The net shortwave radiation, measured at the Earth’s surface. Equal to the difference between SIS and SRS. |
Surface downwelling longwave radiation | SDL | Total downwelling thermal radiation, measured at the Earth’s surface. |
Surface outgoing longwave radiation | SOL | Total upwelling thermal radiation, measured at the Earth’s surface. |
Surface net longwave radiation | SNL | The net longwave radiation, measured at the Earth’s surface. Equal to the difference between SDL and SOL. |
Surface radiation budget | SRB | The total net radiative flux (both short- and longwave) at the Earth’s surface. Equal to the total of SNS and SNL. |
Table 2: Definition of processing levels
Processing level | Definition |
Level-1b | The full-resolution geolocated radiometric measurements (for each view and each channel), rebinned onto a regular spatial grid. |
Level-2 (L2) | Retrieved cloud variables at full input data resolution, thus with the same resolution and location as the sensor measurements (Level-1b). |
Level-3C ( |
Table 2: Definition of processing levels
Processing level
Definition
Level-1b
The full-resolution geolocated radiometric measurements (for each view and each channel), rebinned onto a regular spatial grid.
Level-2 (L2)
Retrieved cloud variables at full input data resolution, thus with the same resolution and location as the sensor measurements (Level-1b).
L3C) | Cloud properties of Level-2 orbits of one single sensor combined (averaged) on a global spatial grid. Both daily and monthly products provided through C3S are Level-3C. |
Table 3: Definition of various technical terms used in the document
Jargon | Definition |
Brokered product
TCDR | A Thematic Climate Data Record is a consistently processed time series of a geophysical variable. The time series should be of sufficient length and quality. |
ICDR | An Interim Climate Data Record (ICDR) denotes an extension of TCDR, processed with a processing system as consistent as possible to the generation of TCDR. |
Brokered product | The C3S Climate Data Store (CDS) provides both data produced specifically for C3S and so-called brokered products. The latter are existing products produced under an independent programme or project which are made available through the CDS. |
Climate Data Store (CDS) | The front-end and delivery mechanism for data made available through C3S. |
It is a platform that provides access to a wide range of climate data, including satellite and in-situ observations, reanalysis and other relevant datasets. | |
Retrieval | A |
Retrieval
numerical data analysis scheme which uses some form of mathematical inversion to derive physical properties from some form of measurement. In this case, the derivation of cloud properties from satellite measured radiances. | |
Forward model | A deterministic model which predicts the measurements made of a system, given its physical properties. The forward model is the function which is mathematically inverted by a retrieval scheme. In this case, the forward model predicts the radiances measured by a satellite instrument as a function of atmospheric and surface state, and cloud properties. |
TCDR
It is a consistently-processed time series of a geophysical variable of sufficient length and quality.
ICDR
An Interim Climate Data Record (ICDR) denotes an extension of TCDR, processed with a processing system as consistent as possible to the generation of TCDR.
CDR
A Climate Data Record (CDR) is defined as a time series of measurements with sufficient length, consistency, and continuity to determine climate variability and change.
Scope of the document
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Scope of the document
This Product User Guide and Specification (PUGS) document is associated with the Climate Data Store (CDS) catalogue entry: Surface radiation budget from 1979 to present derived from satellite observations. This Climate Data Record (CDR) comprises inputs from three sources: (i) brokered products from
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the Cloud Climate Change Initiative (ESA’s Cloud_cci), namely those coming from processing of the Advanced Along-Track Scanning Radiometer (A)ATSR) data
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(also named TCDR (Thematic Climate Data Record)), and two Interim Climate Data Records (ICDR) extensions namely (ii) those produced under this contract for the CDS, specifically those coming from processing of the Sea and Land Surface Temperature Radiometers (SLSTR)
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by Rutherford Appleton Laboratory (RAL) Space and (iii) those produced under this contract for the CDS, specifically those coming from processing of the SLSTR by Brockmann Consult (BC).
Both of the ICDRs mentioned above are produced using the Optimal Retrieval of Aerosol and Cloud (ORAC) algorithm, using the Community Cloud for Climate (CC4CL) processor under the ESA Cloud_cci project.
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One ICDR was produced by Rutherford Appleton Laboratory (RAL) Space for the period 01/2017 to 06/2022 and the other ICDR by Brockmann Consult (BC) for the period 07/2022 to 12/2023.
This document provides information on how to use these products and it is not part of the official CCI documentation, but produced only in the scope of the brokering to the CDS.
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Executive summary
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Executive summary
The ESA Climate Change Initiative (CCI) Surface Radiation Budget Thematic Climate Data Record (TCDR) is a brokered product from the ESA Cloud_cci project, while the extension Interim CDR (ICDR) produced from the Sea and Land Surface Temperature Radiometers (SLSTR) is produced specifically for C3S. The product is generated
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using the Community Cloud for Climate (CC4CL) processor, based on the Optimal Retrieval of Aerosol and Cloud (ORAC) algorithm. The Surface Radiation Budget is a product of the Broadband Radiative Flux Retrieval (BRFR) module of CC4CL, which uses the cloud properties produced by ORAC to compute broadband radiative flux values.
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The ICDR product was generated by RAL Space for the period from 01/2017 up to 06/2022 and by BC for the period from 07/2022 to 12/2023.
The
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Cloud_cci dataset comprises 17 years (1995-2012) of satellite-based measurements derived from the Along Track Scanning Radiometers (ATSR-2 and AATSR) onboard the ESA second European Research Satellite (ERS-2) and ENVISAT. This
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TCDR is partnered with the ICDR produced from the Sentinel-3 Sea and Land Surface Temperature Radiometers (SLSTR), beginning in 2017 (Sentinel-3A) and 2018 (Sentinel-3B), when data from each platform became available.
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In addition to the individual data from each platform, a merged product is provided from 10/2018 onwards.
The dataset provides
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level-3 data (monthly means) on
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two grids: (1) regular equal angle global latitude-longitude grid (2) regular equal area global latitude-longitude grid (
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the second option solely for the merged product from 07/2022 on). An overview of the various data producers, satellites, grids and time coverages for the ICDRs is shown in section 1, Figure 1-1.
Both grids have a resolution of 0.
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5°× 0.
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5° and
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include these products: the Surface Incoming and Reflected Shortwave radiation (SIS and SRS respectively), the Surface Downwelling and Outgoing Longwave radiation (SDL and SOL respectively), the Surface Net Shortwave and Longwave radiation (SNS and SNL), and the total Surface Radiation Budget (SRB).
These products are brokered to (in the case of (A)ATSR) or produced for the Climate Data Store (in the case of SLSTR) by the Copernicus Climate Change Services (C3S). The respective data products (monthly means) are first described in terms of their input data and a brief overview of the algorithms is provided; their target requirements in the scope of C3S and achieved performances are given; relevant information for usage is provided. The latter comprises geographical grid specifications, the data format, naming conventions, and the acknowledgement policy.
Anchor section1 section1
1.
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Cloud_cci global monthly
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Surface Radiation Budget products
The Cloud_cci global monthly Surface Radiation Budget
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TCDR, version 3.0, is brokered to the CDS by the C3S from STFC RAL Space. The SLSTR ICDR,
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version 3.1.1 and version 4.0 up to June 2022, are supplied to the CDS via the same route and uses the same processing software and infrastructure as the
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TCDR. The SLSTR ICDR, version 4.0 for the period from 07/2022 to 12/2023 is processed on BC infrastructure using the same processing software for Level-2, the additional grid version (equal area) was processed using the Calvalus aggregator [D6] for the Level-3 step. Although the format of the brokered data products differs from the official CCI products, the intellectual property rights remain with the Cloud_cci team.
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In detail, the official daily and monthly files from Cloud_cci contain more than 180 variables, but the specified C3S format splits them into separate parts per ECV. That way, each file has a reduced data amount as well as an increased usability. The landing page for the official CCI products is https://climate.esa.int/en/projects/cloud/. Detailed information on the cloud products and their use are outlined in the CCI Product User Guide [D3].
The product provides estimates of monthly mean global broadband surface radiation over land and ocean from the (A)ATSR series of satellite sensors, on a 0.
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5°×0.5° latitude-longitude grid from mid-1995 until early 2012. The SLSTR based ICDR extends the coverage, with a five-year gap, from 2017 onwards and is only available through the CDS. Version 3.1.1 of the ICDR provides data from a single SLSTR (flying on board either Sentinel-3a or -3b), while version 4.0 combines data from both SLSTR instruments into a single combined product (starting with the launch of the Sentinel-3b in late 2018).
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All monthly means are provided on an equal angle projection. In addition, the product from 07/2022 onwards is provided on an equal area projection as well (see Figure 1-1 for an overview).
Figure 1-1: Overview of data producers, satellites, time coverages and grids for the ICDRs. Products above/below the horizontal black line are produced by RAL Space/Brockmann Consult (BC) respectively, while data from 07/2022 onwards is provided on two different grids.Anchor figure1_1 figure1_1
1.1 Product description
The Cloud_cci product brokered to the CDS consists of surface radiation derived from the (A)ATSR instruments; specifically:
ATSR-2, which flew on the second European Research
1.1 Product description
The Cloud_cci product brokered to the CDS consists of surface radiation derived from the (A)ATSR instruments; specifically:
- ATSR-2, which flew on the second European Research
Satellite (ERS-2) from June 1995 until January 2008. ERS-2 lost global coverage in June 2003, due to failure of the onboard data storage; Cloud_cci data do not extent beyond this date (thus providing approximately one-year of overlap with the succeeding AATSR product).
Advanced-ATSR (AATSR), which flew on ENVISAT from May 2002 until the satellite’s failure in April 2012.
When referred to in terms of a continuous data record, these two instruments are commonly described as (A)ATSR. The preceding ATSR-1 instrument lacked the visible-NIR channels provided by (A)ATSR and thus isn’t included in the Cloud_cci product.
The Cloud_cci also produced cloud and radiation products from the Advanced Very High Resolution Radiometer (AVHRR) series of instruments and the Moderate Resolution Imaging Spectroradiometer (MODIS), using a common retrieval technique, but only the (A)ATSR products are brokered to the CDS.
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The ICDR consists of the same essential climate variables (ECVs) derived from the SLSTR instruments flying on board the Sentinel-3A (from 2017 onwards) and Sentinel-3B (from 2018 onwards).
The analysis algorithm applied in producing the Cloud_cci products is the Optimal Retrieval of Aerosol and Clouds (ORAC), with broadband flux calculations performed using the BUGSRad radiative transfer code (Stephens et al., 2001). The overall data processing system used in the project is referred to as Community Cloud for Climate (CC4CL), and these are detailed in the C3S ATBD [D1], Cloud_cci ATBD [D2], Cloud_
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cci CC4CL Broadband Radiative Flux Retrieval ATBD [
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D4], Sus et al. (2018) and McGarragh et
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al. (2018).
The brokered TCDR is extended, with a five-year gap, from 2017 with an ICDR derived from the SLSTR instruments, which fly onboard the Copernicus operational Sentinel-3 satellites. From late 2018, a second Sentinel-3 platform is available, which doubles the spatial coverage of SLSTR and allows for nearly complete global coverage twice a day. The SLSTR product is produced using the same processing chain as the (A)ATSR TCDR.
1.2 Target requirements
The target requirements for SRB observations are laid-out in the Target Requirements and Gap Analysis Document [D5], but are summarised here. These requirements originate from the WMO Global Climate Observing System (GCOS) initiative, which defines and lays down targets for the observation of ECVs. It should be noted that GCOS requirements are targets for what should be achievable through Earth observation and are often not attainable using existing or historical observing systems. Table 1-1 provides an overview of the GCOS requirements for the surface radiative balance.
Table 1-1: GCOS targets for surface radiation budget ECVs. Note that the Cloud_cci doesn't meet the requirement for resolving the diurnal cycle due to the nature of the satellite observations, but exceeds the spatial resolution and aims to achieve the uncertainty and stability requirements.Anchor table1_1 table1_1
Quantity | Cloud_cci variable | Targets |
Surface ERB longwave | snl |
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Surface ERB shortwave | sns |
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1.3 Data usage information
Cloud_cci products are provided in NetCDF (version 4), which are compliant with the conventions CF 1.8 and the NASA Global Change Master Directory (GCMD) Science Keywords vocabulary. Filenames follow the structure:
C3S-312bL1-L3C-MONTHLY-SRB-INST_ORAC_PLATFORM_YYYYMM_fvVVV.nc,
where INST and PLATFORM refer to the instrument and platform from which data originates (either ATSR2 and ERS2, or AATSR and ENVISAT for the CDRTCDR, or SLSTR and Sentinel-3a or -3b for the ICDR), EA is added for the additional equal area grid and left out for the equal angle grid, and YYYYMM provides the year and month covered by the monthly mean product, and VVV V.V denotes the product version (3.0 for the TCDR, 3.1 for the ICDR).
The list of surface radiation properties, the variable names used within the NetCDF data files and their units are given
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in Table 1-2.
Data are provided as monthly means of surface radiation properties, on a regular latitude-longitude grid, with a spacing of 0.
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5° in both dimensions (thus grid centres lie at -89.
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75°, -89.
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25°, -88.
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75°, …, 89.
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75° in latitude and -179.
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75°, -179.
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25°, -178.
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75°, …, 179.
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75° in longitude).
These values are monthly averages of estimated daily mean radiative fluxes, derived from
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satellite observations made at a fixed local solar time of 10:00 for ENVISAT and both Sentinel-3s, and 10:30 for ERS-2. Thus, the product does not contain any information on the diurnal variability of surface radiation (due to changes in cloud cover and cloud properties for example). Furthermore, the narrow swath of the (A)ATSR instruments means that only approximately 1/3 of the globe is covered each day, whereas the SLSTR based products provide almost global daily coverage. The user is referred to the ATBDs [D1, D2
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] for details of the algorithms used in this process.
Table 1-2: Surface Radiation Budget variables included in Cloud_cci TCDR and SLSTR ICDR monthly products.Anchor table1_2 table1_2
Property | Unit | Variable name | Comment |
Surface incoming solar radiation | Wm-2 | sis | |
Surface reflected solar radiation | Wm-2 | srs | |
Surface net solar radiation | Wm-2 | sns | Equivalent to "Surface ERB shortwave" GCOS ECV and calculated as sns = sis – srs. |
Surface downwelling longwave radiation | Wm-2 | sdl | |
Surface outgoing longwave radiation | Wm-2 | sol | |
Surface net longwave radiation | Wm-2 | snl | Equivalent to "Surface ERB longwave" GCOS ECV and calculated as snl = sdl – sol. |
Total surface radiation budget | Wm-2 | srb | Calculated as srb = (sis + sdl) - (srs + sol). |
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2. Data access information
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2.1 Data access through CCI
The original repository for the CCI formatted L3 v3.0
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TCDR data can be accessed through the Cloud_cci homepage https://climate.esa.int/en/projects/cloud/data/, as can all relevant documentation from the project. It should be noted that Cloud_cci L3 data is not in the same format as data brokered to the CDS, however the same L2 retrieval output was used to produce both products.
Cloud_cci data should also be available through the ESA CCI data
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portal https://
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climate.esa.int/en/data/#/dashboard, which provides online data mining, analysis and visualization tools for CCI data through the CCI Toolbox.
Only the
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(A)ATSR based
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TCDR is available through the ESA_cci data portal (original provider) as well as the CDS (brokered from CCI within the C3S Project),
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while SLSTR data
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is only supplied
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by the CDS.
2.2 Data access through the CDS
Within C3S, the distribution
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is through the CDS (https://cds.climate.copernicus.eu/) where documentation created for the inclusion of the data in the CDS, such as this PUGS,
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is also
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provided.
2.3 Product ordering process
You need to be registered and logged in to order products in the CDS. A login is provided upon registration, all products in the CDS are delivered free of charge.
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