CLARA-A1: the CM SAF cloud, albedo and radiation dataset from 28 yr of global AVHRR data

Abstract

A new satellite-derived climate dataset – denoted CLARA-A1 ("The CM SAF cLoud, Albedo and RAdiation dataset from AVHRR data") – is described. The dataset covers the 28-yr period from 1982 until 2009 and consists of cloud, surface albedo and radiation budget products derived from the AVHRR (Advanced Very High Resolution Radiometer) sensor carried by polar orbiting operational meteorological satellites. Its content, anticipated accuracies, limitations and potential applications are described. The dataset is produced by the EUMETSAT Climate Monitoring Satellite Application Facility (CM SAF) project. <br><br> The dataset has its strengths in the long duration, its foundation upon a homogenized AVHRR radiance data record, and in some unique features, e.g. the availability of 28 yr of summer surface albedo and cloudiness parameters over the polar regions. Quality characteristics are also well investigated and particularly useful results can be found over the tropics, mid- to high-latitudes and over nearly all oceanic areas. <br><br> Being the first CM SAF dataset of its kind, an intensive evaluation of the quality of the datasets was performed and major findings wrt. to merits and shortcomings of the datasets are reported. However, the CM SAF's long-term commitment to perform two additional reprocessing events within the time frame 2013–2017 will allow a proper handling of limitations as well as upgrading the dataset with new features (e.g. uncertainty estimates) and extension of the temporal coverage

CLARA-SAL: a global 28 yr timeseries of Earth's black-sky surface albedo

“…Considering these results, we choose not to adjust the in situ measurements for any blue-sky/black-sky albedo difference. This decision is also supported by the fact that our validation strategy is based on exclusive selection of confirmed clear-sky in situ data for validation reference, based on the CM SAF cloud mask product (Karlsson et al, 2013). Sites where typical AOD concentrations are large will most likely show poorer correspondence in any case owing to the constant AOD in the atmospheric correction.…”

“…This homogenization of the underlying radiance data record significantly diminishes albedo variation resulting from differences in calibration across the 11 different AVHRR instruments. This radiance data record is common to all CLARA-A1 products (Karlsson et al, 2013).…”

“…The timeseries has been created in the Satellite Application Facility on Climate Monitoring (CM SAF) project of EUMET-SAT as a part of the CMSAF cLouds, Albedo and RAdiation (CLARA) first release product family (Karlsson et al, 2013). This timeseries, specifically called CLARA-A1-SAL (from AVHRR 1st Release -Surface ALbedo), describes the global broadband (0.25-2.5 µm) directional-hemispherical reflectance (DHR) of terrestrial surfaces -or black-sky albedo as it is also known.…”

On the optimal method for evaluating cloud products from passive satellite imagery using CALIPSO-CALIOP data: example investigating the CM SAF CLARA-A1 dataset

“…Here, we will concentrate on the evaluation of the first two products. For a full description of the dataset the reader is referred to Karlsson et al (2013).…”

“…The acronym stands for the Climate Monitoring Satellite Application Facility (CM SAF -see www.cmsaf.eu and Schulz et al, 2009) Clouds, Albedo, and Radiation dataset from AVHRR data (Karlsson et al, 2013). It is based on global historic Advanced Very High Resolution Radiometer (AVHRR) data from the polar-orbiting NOAA satellites covering the period 1982 until 2009.…”