Page tree

Skip to end of metadata
Go to start of metadata

Table of Contents

Acronyms

Acronym

Description

ADS

Atmosphere Data Store

AOD

Aerosol optical depth

AM

Ammonium

APOLLO

AVHRR Processing scheme Over cLouds, Land and Ocean

APOLLO_NG

APOLLO Next Generation

ASCII

American Standard Code for Information Interchange

BC

Black carbon

BHI

Beam Horizontal Irradiation

BNI

Beam Normal Irradiation

BRDF

Bidirectional reflectance distribution function

CAMS

Copernicus Atmospheric Monitoring Service

CRS

CAMS Radiation Service

CSV

comma/semicolon separated data format

DHI

Diffuse Horizontal Irradiation

DU

Dust

GHI

Global Horizontal Irradiation

Heliosat-4

All-sky method

MACC

Monitoring Atmospheric Composition and Climate

McClear

Cloud-free method

MODIS

Moderate-resolution Imaging Spectroradiometer

MSG

Meteosat Second Generation

netCDF

Network common data format

NI

Nitrate

OR

Organic matter

ISO

International Organization for Standardization

SS

Sea salt

SU

Sulphate

TST

True Solar Time

UT

Universal Time

Introduction

The CAMS Radiation Service is designed to meet the requirements that have been specified for the Copernicus Atmosphere Monitoring Service (CAMS). The precursor projects MACC and MACC-II/-III prepared the CAMS Radiation Service in terms of implementation, sustained operation and availability. It was ensured that the service lines have been designed to best meet both the requirements of downstream service providers and end users at the European, national and local levels, and the requirements of the global scientific user community. This page provides a high level overview of the solar radiation service; more details can be found in the Section Detailed documentation.

Solar radiation service 

The CAMS solar radiation service provides historical values (2004 to present) of global (GHI), direct (BHI) and diffuse (DHI) solar irradiation, as well as direct normal irradiation (BNI). The aim is to fulfil the needs of European and national policy developments and the requirements of both commercial and public downstream services. The service supports e.g. planning, monitoring, efficiency improvements, and the integration of solar energy systems into energy supply grids.

Irradiation depends on various atmospheric quantities, such as cloud cover, aerosol concentrations, water vapour and ozone concentrations. Other properties, such as ground albedo and ground elevation, are also taken into account. For clear-sky conditions, an irradiation time series is provided for any location in the world using information on aerosol, ozone and water vapour from the CAMS global forecasting system. Because high-resolution cloud information is directly inferred from satellite observations, the irradiation time series for cloudy conditions are currently only available for the field-of-view of the Meteosat Second Generation (MSG) satellite, which is roughly Europe, Africa, the Atlantic Ocean and the Middle East.

Input quality control, regular quarterly benchmarking against ground stations, and regular monitoring the consistency and detecting possible trends is performed.

Detailed documentation

A detailed User Guide is available here: User Guide to the CAMS Radiation Service (CRS)

Evaluation and Quality Assurance reports

Quarterly reports are made routinely available on the CAMS web page.

Data products

Data is offered via the Copernicus Atmosphere Data Store (ADS) in both ASCII and NetCDF format.

Additionally, an ASCII "expert mode" format can be selected which contains in addition to the irradiation, all the input data used in their calculation (aerosol optical properties, water vapour concentration, etc). This additional information is only meaningful in the time frame at which the calculation is performed and so is only available at 1-minute time steps in universal time (UT).

Table 1: Overview of key characteristics

 

Clear-Sky (McClear)

All-Sky (Heliosat-4)

ADS nameCloud-free conditions onlyBoth cloud-free and actual weather conditions

Type of product

Point data, time-series

Parameters

GHI, DHI, BHI, BNI

Geographical area

global

Europe / Africa / Middle East / Atlantic Ocean
(Meteosat Second Generation
 field of view)

Horizontal resolution

Interpolated to point of interest from various spatial input data resolutions

Time coverage

from 2004-01-01 to
(current – 2 days)

from 2004-02-01 to
(current – 2 days)

Temporal resolution

1 min, 15 min, 1 h, 1 day, 1 month
Following meteorological standards, the time given for an irradiation value is the end of the integration period.

Data format

ASCII (CSV), NetCDF

Data file size

File size depends on the temporal resolution. Largest files are in 1 min temporal resolution and the CSV data format
(e.g. 60 MB for a 1 year time series in the standard output mode and 10 MB if zipped;
138 MB for a 1 year time series in the expert mode and 19 MB if zipped)

Data access

Atmosphere Data Store

Processing

on request; data normally available within a few minutes

Update of the databases

2 days delayed mode

The CAMS Radiation Service CSV formatted products are presented as a metadata header section, followed by lines of values (columns). The metadata header section helps the user to understand the data, and describing the various features of the products. These metadata are written as text in the delivered file, and conform to the ISO standard where available. Currently these metadata are:

  • title: title of the time-series, e.g., “CAMS Radiation Service v3.2 all-sky irradiation (derived from satellite data)”,
  • content: a short description of the content of the product, e.g., “A time-series of solar radiation received on horizontal plane and plane always normal to the sun rays at ground level.”,
  • provider: name of the provider, e.g., “MINES ParisTech (France)”,
  • date begin, date end: dates of the beginning and end of the period. The date follows the ISO 8601 standard, e.g. 2004-01-01T01:00:00.000.
  • site latitude and longitude: geographical coordinates of the site, positive North and positive Earth. The ISO 19115 standard is used,
  • elevation: elevation above sea level in m,
  • time reference: time system used: Universal Time (UT), or True Solar Time (TST). This metadata is present only when the period of integration is less than 1 day,
  • summarization: period during which the energy is summed up to obtain a power average, e.g., 15 min,
  • sampling rate: period with which the resulting irradiation is sampled. Usually, the sampling rate is set equal to summarization,
  • noValue: the code denoting the absence of value, e.g. NaN (not a number).The content of each column is described as a free text.

Each line corresponds to an instance of output observation data for a given period. The typical content of a line is:

  • instance of output observation data for a given period,
  • irradiation at the top of the atmosphere,
  • clear-sky irradiation value at ground level, e.g. Clear Sky GHI
  • all-sky irradiation value at ground level, e.g., GHI,
  • reliability code, ranging from 0 to 1. The exact content of a line depends on the type of product and the description is provided in the metadata. This is why metadata are included in the file header as plain text.

Standard output variables

Main Variable NamesNetCDF UnitsDescription
BHIWh m-2

All-sky direct (beam) irradiation, i.e., the direct part of the surface solar downward irradiation integrated over the whole spectrum available at ground level, on a horizontal surface

BNIWh m-2All-sky direct (beam) normal Irradiation. Part of the radiation that is received from the direction of the sun by a plane facing the sun.
DHIWh m-2All-sky diffuse irradiation, i.e., the diffuse part of the surface solar downward irradiation integrated over the whole spectrum available at ground level, on a horizontal surface.
GHIWh m-2All-sky global irradiation, i.e., the surface solar downward irradiation integrated over the whole spectrum available at ground level, on a horizontal surface.

Expert mode variables

For expert users, all input and output variables are provided in the ‘detailed info expert output mode’. It can only be retrieved when requesting 1 min resolved time series from the Atmosphere Data Store. Besides the standard outputs, it provides:

  • Irradiation on a horizontal plane at the top of atmosphere
  • Clear sky irradiation values:
    • Clear sky GHI. Clear sky global irradiation on a horizontal plane at ground level
    • Clear sky BHI. Clear sky direct (beam) irradiation on a horizontal plane at ground level
    • Clear sky DHI. Clear sky diffuse irradiation on a horizontal plane at ground level 
    • Clear sky BNI. Clear sky direct (beam) irradiation on a mobile plane at normal incidence following the sun 
  • All sky irradiation values:
    • All sky GHI. Clear sky global irradiation on horizontal plane at ground level
    • All sky BHI. Clear sky direct (beam) irradiation on horizontal plane at ground level
    • All sky DHI. Clear sky diffuse irradiation on horizontal plane at ground level
    • All sky BNI. Clear sky direct (beam) irradiation on mobile plane at normal incidence following the sun 
  • Solar zenith angle for the middle of the summarization (deg)
  • Atmospheric profile code: afglus=U.S. standard, afglt=tropical, afglms=midlatitude summer, afglmw=midlatitude winter, afglss=subarctic summer, afglsw=subarctic winter
  • Total column content of ozone (Dobson unit)
  • Total column content of water vapour (kg/m2)
  • AOD BC. Partial aerosol optical depth at 550 nm for black carbon
  • AOD DU. Partial aerosol optical depth at 550 nm for dust
  • AOD SS. Partial aerosol optical depth at 550 nm for sea salt
  • AOD OR. Partial aerosol optical depth at 550 nm for organic matter
  • AOD SU. Partial aerosol optical depth at 550 nm for sulphate
  • AOD NI. Partial aerosol optical depth at 550 nm for nitrate. This quantity was introduced in July 2019 and will have zero values before – indicating unavailability.
  • AOD AM. Partial aerosol optical depth at 550 nm for ammonium. This quantity was introduced in July 2019 and will have zero values before – indicating unavailability.
  • Deprecated and replaced by AOD NI: AOD 550. Aerosol optical depth at 550 nm
  • Deprecated and replaced by AOD AM: AOD 1240. Aerosol optical depth at 1240 nm
  • Deprecated, but kept for format consistency: alpha Ångström coefficient for aerosol. It is set to zero values.
  • Deprecated, but kept for format consistency: Aerosol type. Type of aerosol: -1=no value, 5=urban, 7=continental clean, 8=continental polluted, 9=continental average 10=maritime clean, 11= maritime polluted, 12=maritime tropical, 13=antarctic, 14=desert
  • MODIS-like BRDF (bidirectional reflectance distribution function) parameter fiso
  • MODIS-like BRDF (bidirectional reflectance distribution function) parameter fvol
  • MODIS-like BRDF(bidirectional reflectance distribution function) parameter fgeo
  • Ground albedo
  • Cloud optical depth (value of the nearest acquisition time of the pixel, not interpolated over time)
  • Cloud coverage of the pixel (percentage from 0 to 100, value of the nearest acquisition time of the pixel, not interpolated over time)
  • Cloud type (value of the nearest acquisition time of the pixel, not interpolated over time) -1=no value, 0=no clouds, 5=low-level cloud, 6=medium-level cloud, 7=high-level cloud, 8=thin cloud
  • non-bias corrected all-sky radiation values
    • non-corrected all sky GHI. Clear sky global irradiation on horizontal plane at ground level
    • non-corrected all sky BHI. Clear sky direct (beam) irradiation on horizontal plane at ground level
    • non-corrected all sky DHI. Clear sky diffuse irradiation on horizontal plane at ground level
    • non-corrected all sky BNI. Clear sky direct (beam) irradiation on mobile plane at normal incidence, following the sun 

Users may:

  • make use of this information to establish an extended bias correction based on their own localised ground observations;
  • use this transparency about all input parameters to run their own solar radiation retrieval schemes;
  • contribute easily to evaluation and method development of Heliosat‑4 by having access to all input variables;
  • develop downstream services by making use of the knowledge of all input parameters e.g. in artificial intelligence methods

Note should be taken that the content of the detailed info mode may change depending on the version of Heliosat‑4 or McClear. Each product contains a detailed description of its content and the user should refer to it.

Known issues and version updates

DateVersionDescription 

2021-06

v4.0 (current)

Since 2013, CAMS Radiation service used the cloud retrieval scheme APOLLO. The version 4.0 of CAMS Radiation Service includes a new version APOLLO Next Generation (APOLLO_NG) that improves cloud detection using fuzzy logic.
Fix in the MSG satellite projection handling for all data before 12/2017.
A new global bias correction was implemented.

2018-06

v3.2

Fix of a mathematical bug in the (latitude, longitude) position of the pixels of the Meteosat satellite images.

2018-03

v3.1

CAMS McClear benefits from the successive enhancements of the Aerosol Optical Depth versions. McClear version, and consequently CAMS radiation service version as well, have been incremented from 3.0 to 3.1. Results are slightly modified in October 2012 and September-November 2015.

2017-10

v3

McClear clear sky model v3
New empirical  bias correction algorithm

2015-10

v2.7

McClear v2.7

2015-07

v2.6

Bug fixed in verbose expert mode

2015-02

v2.6

Bug fixed in the filling of MACC AOD databases

2015-01

v2.6

Bug fixed bug for cloud coverage > 100%
Add a verbose expert mode for the one minute requests
Edition format file version 2

2014-11

v2.5

APOLLO data coverage extension: 2004-02-01 to D-2

2014-11

v2.4

Call to McClear v2.4

2014-08

v2.3

Call to McClear v2.3 Bug fixed in APOLLO data interpolation


v2.2

does not exist (synchronization with McClear versions)

2014-07

v2.1

Bug fixed for the shift of one pixel in APOLLO files import

2013-07

v2.0

Edition format file version 1

How to acknowledge and cite the data

The use of the CAMS Radiation Service data should be acknowledged as indicated below:

All users of data uploaded from the Atmosphere Data Store (ADS) must:

(1) provide clear and visible attribution to the Copernicus programme by citing the web catalogue page:

CAMS solar radiation time-series. Copernicus Atmosphere Monitoring Service (CAMS) Atmosphere Data Store (ADS). (Accessed on DD-MMM-YYY), https://ads.atmosphere.copernicus.eu/cdsapp#!/dataset/cams-solar-radiation-timeseries?tab=overview

(2) acknowledge according to the data licence (i.e. licence to use Copernicus products (Clause 5 in particular)

(3) Cite the relevant peer-review publication for the CAMS-Radiation Service:

Qu, Z., Oumbe, A., Blanc, P., Espinar, B., Gesell, G., Gschwind, B., Klüser, L., Lefèvre, M., Saboret, L., Schroedter-Homscheidt, M., and Wald L.: Fast radiative transfer parameterisation for assessing the surface solar irradiance: The Heliosat-4 method, Meteorol. Z., 26, 33-57, doi: 10.1127/metz/2016/0781,2017. Available for download at https://www.schweizerbart.de/papers/metz/detail/26/87036/Fast_radiative_transfer_parameterisation_for_asses?af=crossref.

and for the CAMS clear-sky time series:

Lefèvre, M., Oumbe, A., Blanc, P., Espinar, B., Gschwind, B., Qu, Z., Wald, L., Schroedter-Homscheidt, M., Hoyer-Klick, C., Arola, A., Benedetti, A., Kaiser, J., W., and Morcrette, J.-J.: McClear: a new model estimating downwelling solar radiation at ground level in clear-sky conditions, Atmos. Meas. Tech., 6, 2403–2418, doi: 10.5194/amt-6-2403-2013, 2013. Available for download at http://www.atmos-meas-tech.net/6/2403/2013/amt-6-2403-2013.pdf

Gschwind, B., Wald L., Blanc, P., Lefèvre, M., Schroedter-Homscheidt, M., Arola, A., 2019. Improving the McClear model estimating the downwelling solar radiation at ground level in cloud free conditions – McClear-V3., Meteorol. Z./Contrib. Atm. Sci., 28, 2, 147-163, doi:10.1127/metz/2019/0946. Available for download at https://www.schweizerbart.de/papers/metz/detail/28/90593/Improving_the_McClear_model_estimating_the_downwelling_solar_radiation_at_ground_level_in_cloud_free_conditions_McClear_v3

References 

Qu, Z., Oumbe, A., Blanc, P., Espinar, B., Gesell, G., Gschwind, B., Klüser, L., Lefèvre, M., Saboret, L., Schroedter-Homscheidt, M., and Wald L.: Fast radiative transfer parameterisation for assessing the surface solar irradiance: The Heliosat-4 method, Meteorol. Z., 26, 33-57, doi: 10.1127/metz/2016/0781,2017. Available for download at https://www.schweizerbart.de/papers/metz/detail/26/87036/Fast_radiative_transfer_parameterisation_for_asses?af=crossref.

Lefèvre, M., Oumbe, A., Blanc, P., Espinar, B., Gschwind, B., Qu, Z., Wald, L., Schroedter-Homscheidt, M., Hoyer-Klick, C., Arola, A., Benedetti, A., Kaiser, J., W., and Morcrette, J.-J.: McClear: a new model estimating downwelling solar radiation at ground level in clear-sky conditions, Atmos. Meas. Tech., 6, 2403–2418, doi: 10.5194/amt-6-2403-2013, 2013. Available for download at http://www.atmos-meas-tech.net/6/2403/2013/amt-6-2403-2013.pdf

Gschwind, B., Wald L., Blanc, P., Lefèvre, M., Schroedter-Homscheidt, M., Arola, A., 2019. Improving the McClear model estimating the downwelling solar radiation at ground level in cloud free conditions – McClear-V3., Meteorol. Z./Contrib. Atm. Sci., 28, 2, 147-163, doi:10.1127/metz/2019/0946. Available for download at https://www.schweizerbart.de/papers/metz/detail/28/90593/Improving_the_McClear_model_estimating_the_downwelling_solar_radiation_at_ground_level_in_cloud_free_conditions_McClear_v3


This document has been produced in the context of the Copernicus Atmosphere Monitoring Service (CAMS).

The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of CAMS on behalf of the European Union (Delegation Agreement signed on 11/11/2014). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.

The user thereof uses the information at its sole risk and liability. For the avoidance of all doubts, the European Commission and the European Centre for Medium-Range Weather Forecasts has no liability in respect of this document, which is merely representing the authors view.