Abstract
Abstract. We present a novel 28 yr dataset of Earth's black-sky surface albedo, derived from AVHRR instruments. The dataset is created using algorithms to separately derive the surface albedo for different land use areas globally. Snow, sea ice, open water and vegetation are all treated independently. The product features corrections for the atmospheric effect in satellite-observed surface radiances, a BRDF correction for the anisotropic reflectance properties of natural surfaces, and a novel topography correction of geolocation and radiometric accuracy of surface reflectance observations over mountainous areas. The dataset is based on a homogenized AVHRR radiance timeseries. The product is validated against quality-controlled in situ observations of clear-sky surface albedo at various BSRN sites around the world. Snow and ice albedo retrieval validation is given particular attention using BSRN sites over Antarctica, Greenland Climate Network stations on the Greenland Ice Sheet (GrIS), as well as sea ice albedo data from the SHEBA and Tara expeditions. The product quality is found to be comparable to other previous long-term surface albedo datasets from AVHRR.
Highlights
Accurate determination of Earth’s surface albedo is required for both characterizing the atmosphere–surface boundary layer in atmospheric studies, and resolving the radiative budget at surface level for climate monitoring studies
The discussion goes deeper into the SAL algorithm itself as we describe the process of retrieving surface albedo from the Advanced Very High Resolution Radiometer (AVHRR) measurements
4.1 Validation against ground truth. The validation of this first release of the CLARA-SAL dataset was done using in situ albedo observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) and Tara ice camps, and the Baseline Surface Radiation Network (BSRN) and Greenland Climate Network (GC-Net) station networks as reference data (Ohmura et al, 1998; Steffen et al, 1996)
Summary
Accurate determination of Earth’s surface albedo is required for both characterizing the atmosphere–surface boundary layer in atmospheric studies, and resolving the radiative budget at surface level for climate monitoring studies. Most such studies require the surface albedo to be known over a large area with continuous monitoring. This timeseries, called CLARA-A1-SAL (from AVHRR 1st ReleOasce e– aSunrfaScecAieLnbecdoe), describes the global broadband (0.25–2.5 μm) directional-hemispherical reflectance (DHR) of terrestrial surfaces – or black-sky albedo as it is known. In addition to describing the dataset characteristics and the processing algorithm behind it, we will present results from an extensive validation effort aimed at determining thSe oallbieddoEreatrrietvhal accuracy.
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