This data set is only available for a restricted user group, please contact us if you want to access these data.
Coverage, spatial and temporal resolution
Period and temporal resolution:
- 1982-01 to 2015-12
Coverage and spatial resolution:
- 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
- Altitude: following terrain
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 solar zenith angle and the number N of valid albedo values used to compute the statistical moments. It is recommended to use only data with N larger than 20.
Because a few of the additional data required for the processing (see description) are missing in 2015, it is recommended to not over-interpret results that seem to be specific for that particular year.
Evaluation of the product confirms that the target accuracy of 25% difference relative to the in-situ observation is met for nearly all sites used for the evaluation within the period 1992-2014. Mean absolute differences to surface albedo from evaluation data sets are often below 5%.
Browsing through the data set reveals that areas of a highly variable aerosol load, i.e. aerosol optical depth (AOD) and/or frequent cloud cover, can have artificially large surface albedo values. South China and Indonesia are candidates here.
Limitations and artifacts may also originate from extremely clear atmospheres (Antarctic interior), mixed cloud / snow covers, and land cover classifications not representing the actual conditions.
For more information about the quality and limitations of the data set we refer to the CM-SAF Product User Guide (PUM) and the CM-SAF Validation report in the references.
Climate Monitoring Satellite Application Facility (CM-SAF)
email: contact.cmsaf (at) dwd.de
ICDC / CEN / University of Hamburg
email: stefan.kern (at) uni-hamburg.de
The citation for this data set is:
Karlsson, Karl-Göran; Anttila, Kati; Trentmann, Jörg; Stengel, Martin; Meirink, Jan Fokke; Devasthale, Abhay; Hanschmann, Timo; Kothe, Steffen; Jääskeläinen, Emmihenna; Sedlar, Joseph; Benas, Nikos; van Zadelhoff, Gerd-Jan; Schlundt, Cornelia; Stein, Diana; Finkensieper, Stephan; Håkansson, Nina; Hollmann, Rainer; Fuchs, Petra; Werscheck, Martin (2017): CLARA-A2: CM SAF cLoud, Albedo and surface RAdiation dataset from AVHRR data - Edition 2, Satellite Application Facility on Climate Monitoring, DOI:10.5676/EUM_SAF_CM/CLARA_AVHRR/V002, https://doi.org/10.5676/EUM_SAF_CM/CLARA_AVHRR/V002.
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.