Abstract
The albedo is a fundamental component of the processes that govern the energy budget, and particularly important in the context of climate change. However, a satellite-based high-resolution (30 m) albedo product which can be used in the polar regions up to 82.5° latitude during the summer seasons is lacking. To cover this gap, in this study we calculate satellite-based broadband albedo from Landsat 8 OLI and validate it against broadband albedo measurements from in situ stations located on the Antarctic and Greenland icesheets. The model to derive the albedo from raw satellite data includes an atmospheric and topographic correction and conversion from narrow-band to broadband albedo, and at each step different options were taken into account, in order to provide the best combination of corrections. Results, after being cleaned from anomalous data, show a good agreement with in situ albedo measurements, with a mean absolute error between in situ and satellite albedo of 0.021, a root mean square error of 0.026, a standard deviation of 0.015, a correlation coefficient of 0.995 (p < 0.01) and a bias estimate of −0.005. Considering the structure of the model, it could be applied to data from previous sensors of the Landsat family and help construct a record to analyze albedo variations in the polar regions.
Highlights
The albedo has a relevant role in the energy budget studies above all at the Poles, where it is generally high owing to the large fraction of surface area covered with snow and ice
With the intention of validating our satellite derived albedo after the correction process, we considered broadband albedo data from in situ stations located on the Antarctic and Greenland Ice Sheets (Figure 2)
The results are displayed in five different subsections: the first concerns the validation of the albedo retrieval method in comparison with all in situ stations; each specific station dataset is considered, i.e., (i) Institute for Marine and Atmospheric Research Utrecht (IMAU) automatic weather stations (AWSs) [18] and (ii) BSRN stations [17] in Antarctica and (iii) PROMICE AWSs [16] in Greenland
Summary
The albedo has a relevant role in the energy budget studies above all at the Poles, where it is generally high owing to the large fraction of surface area covered with snow and ice. It depends on different factors, i.e., snow metamorphism, including changes in the size and shape of snow grains [3,4,5,6,7], snow density and stratification, the occurrence of various surface morphologies owing to strong and persistent winds (e.g., sastrugi, snow dunes and wind glaze areas), or the presence of blue ice [8,9,10]. While the surface covered by these punctual records can approximate a Landsat satellite pixel [19], it cannot be considered representative of a large area, i.e., an entire glacier or ice sheet [20].
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