Surface Radiation Parameters (CLARA-A2) from EUMETSAT CM-SAF
Topics
- Access
- Description
- Parameters
- Coverage, spatial and temporal resolution
- Data quality
- Contact person
- References
- Data citation
Access
RESTRICTED: This link to the data set is only available for a restricted user group. The data set is only accessible in CEN/MPI net or accessible from external nets with a customer account. Please contact ICDC if you would like to access this data from outside the network.
- View surface radiation data at LAS
- Access surface radiation data via OPeNDAP
- Data access via file system: /data/icdc/land/eumetsat_clara2_surfaceradiation/
Description
CLARA-A2 stands for "CM SAF cLouds, Albedo RAdiation data record, AVHRR-based, Edition 2" and comprises a suite of radiation and cloud parameters derived within the EUMETSAT Climate Monitoring Satellite Application Facility (CM-SAF) from Advanced Very High Resolution Radiometer (AVHRR) data.
Here we offer (for internal users only) and briefly describe the radiation products. Products are also available for surface albedo and clouds at ICDC.
Surface incoming shortwave radiation is computed following Müller et al., 2009 (see references). Cloud detection and masking is carried out with the AVHRR-PPS package (see Dybbroe et al., 2005 under references). Additionally required independent surface albedo and aerosol information is based on climatologies (GADS/OPAC and SARB/CERES), other meteorological information is taken from ERA-Interim reanalysis data. For cloudy grid cells look-up tables are used. The temporal averaging takes into account the diurnal cycle of solar radiation.
The surface outgoing longwave radiation is basically based on respective ERA-Interim data corrected for differences in terrain elevation and spatial resolution.
The surface downwelling longwave radiation is basically as well based on respective ERA-Interim data corrected for terrain elevation and cloud cover effects.
Details about the processing steps can be found in the respective ATBD as well as in the paper of Karlsson et al. (2015) in the references.
We offer version 2.1 of edition 2 of the CLARA data set, i.e. CLARA-A2, for internal use only. Version 2.1 includes version 2.0 which terminates end of 2015.
Last update of data set at ICDC: December 3 2020.
Parameters
| Name | Unit | Comment |
|---|---|---|
| Surface downwelling shortwave radiation (SIS) | W/m² | Also available with daily temporal resolution |
| Surface downwelling shortwave radiation with low accuracy | W/m² | not compliant with CM-SAF target accuracy (e.g. for polar regions) |
| Surface downwelling shortwave radiation standard deviation | W/m² | |
| Number of surface downwelling shortwave radiation observations per grid cell | - | |
| Number of daily averages used for the monthly average value of SIS | - | |
| Clear sky surface downwelling shortwave radiation (SISCLS) | W/m² | Model result |
| Number of daily averages used for the monthly average value of SISCLS | - | |
| Surface downwelling longwave radiation (SDL) | W/m² | |
| Surface downwelling longwave radiation standard deviation | W/m² | |
| Number of surface downwelling longwave radiation observations per grid cell | - | |
| Surface outgoing longwave radiation (SOL) | W/m² |
Coverage, spatial and temporal resolution
Period and temporal resolution:
- 1982-01 to 2019-06
- Monthly
Coverage and spatial resolution:
- Global
- Spatial resolution: 0.25 degrees x 0.25 degrees, equally spaced lat/lon grid (Climate Modeling Grid, CMG)
- Geographic longitude:-179.875°E to 179.875°E
- Geographic latitude: -89.875°N to 89.875°N
- Dimension: 1440 columns x 720 rows
Format:
- NetCDF
Data quality
The data set does not include separate uncertainty estimates.
It does contain, however, information about the standard deviation per grid cell which could be taken as a measure of uncertainty. It contains also information about the number N of valid radiation values per grid cell and the number of days with valid values used to compute the monthly averages. Generally, for a daily average at least 20 observations per grid cell are required. Monthly averages are only derived when at least 20 valid daily averages are available for the respective grid cell.
Evaluation of the product confirms that the target accuracy of 10 W/m² is met for the two surface incoming / downwelling radiation products; for the surface outgoing longwave radiation the target accuracy is not met (14 W/m² is the actual accuracy).
The (often low) total number of satellite overpasses - particularly during the years before 1992 - and hence very low number of overlapping swaths causes many gaps in the surface incoming shortwave radiation product. Because of limited accuracy also over snow-covered areas often no data of the surface incoming shortwave radiation is provided. It can therefore not be recommended to derive large-scale averages from the CLARA-A2 record of this parameter.
Both longwave products depend largely on ERA-Interim atmospheric re-analysis data and are hence not suited for model evaluation.
Details about the validation and evaluation are given in the CM-SAF Validation Report , in the CM-SAF Product User Manual (PUM), as well as in the papers listed in the references.
Contact
Climate Monitoring Satellite Application Facility (CM-SAF)
Helpdesk at www.cmsaf.eu
email: contact.cmsaf (at) dwd.deStefan Kern
ICDC / CEN / University of Hamburg
E-Mail: stefan.kern"AT"uni-hamburg.de
References
Literature:
- ATBD, Algorithm Theoretical Basis Document CM SAF Cloud, Albedo, Radiation data record, AVHRR-based, Edition 2 (CLARA-A2), Surface Radiation (pdf, not barrier free)
- PUM, CM SAF Cloud, Albedo, Radiation dataset, AVHRR-based, Edition 2 (CLARA-A2) Surface Radiation Products Product User Manual (pdf, not barrier free)
- Validation Report, CM SAF Cloud, Albedo, Radiation dataset, AVHRR-based, Edition 2 (CLARA-A2) Surface Radiation Products Validation Report (pdf, not barrier free)
- Karlsson, K.-G., et al., 2017, CLARA-A2: the second edition of the CM SAF cloud and radiation data record from 34 years of global AVHRR data, Atmospheric Chemistry and Physics, 17, 5809-5828, doi:10.5194/acp-17-5809-2017.
- Karlsson, K.-G., et al. 2015, Advancing the uncertainty characterisation of cloud masking in passive satellite imagery: Probabilistic formulations for NOAA AVHRR data, Remote Sens. Environ., 158, 126–139, doi:10.1016/j.rse.2014.10.028.
- Karlsson, K.-G., et al., 2013, CLARA-A1: a cloud, albedo, and radiation dataset from 28 yr of global AVHRR data, Atmospheric Chemistry and Physics, 13, 5351-5367, doi:10.5194/acp-13-5351-2013.
- Heidinger, A.K., et al., 2010, Deriving an inter-sensor consistent calibration for the AVHRR solar reflectance data record, International Journal of Remote Sensing, 31, 6493-6517.
- Hess, M., et al., 1998, Optical properties of aerosol and clouds: The software package OPAC, Bulletin of the American Meteorological Society, 79(5), 831-844.
- Mueller, R., et al., (2009), The CM-SAF operational scheme for the satellite based retrieval of solar surface irradiance - A LUT based eigenvector hybrid approach, Remote Sensing of Environment, 113, 1012-1024, doi://10.1016/j.rse.2009.01.012. (pdf, not barrier free)
- Dybbroe, A., et al, 2005, SAFNWC AVHRR cloud detection and analysis using dynamics thresholds and radiative transfer modelling part I: Algorithm description. Journal of Applied Meteorology, 44, 39-54.
Websites:
Data citation
Please cite the data as follows:
Karlsson, Karl-Göran; Anttila, Kati; Trentmann, Jörg; Stengel, Martin; Solodovnik, Irina; Meirink, Jan Fokke; Devasthale, Abhay; Kothe, Steffen; Jääskeläinen, Emmihenna; Sedlar, Joseph; Benas, Nikos; van Zadelhoff, Gerd-Jan; Stein, Diana; Finkensieper, Stephan; Håkansson, Nina; Hollmann, Rainer; Kaiser, Johannes; Werscheck, Martin (2020): CLARA-A2.1: CM SAF cLoud, Albedo and surface RAdiation dataset from AVHRR data - Edition 2.1, Satellite Application Facility on Climate Monitoring, DOI:10.5676/EUM_SAF_CM/CLARA_AVHRR/V002_01, https://doi.org/10.5676/EUM_SAF_CM/CLARA_AVHRR/V002_01.
All intellectual property rights of the CM SAF products belong to EUMETSAT. The use of these products is granted to every interested user, free of charge. If you wish to use these products, EUMETSAT copyright credit must be shown by displaying the words "copyright (year) EUMETSAT" on each of the products used.
and with the following acknowledgments:
Thanks to ICDC, CEN, University of Hamburg for data support.