16 October 2015 How well can we estimate areal-averaged spectral surface albedo from ground-based transmission in the Atlantic coastal area?
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Abstract
Areal-averaged albedos are particularly difficult to measure in coastal regions, because the surface is not homogenous, consisting of a sharp demarcation between land and water. With this difficulty in mind, we evaluate a simple retrieval of areal-averaged surface albedo using ground-based measurements of atmospheric transmission alone under fully overcast conditions. To illustrate the performance of our retrieval, we find the areal-averaged albedo using measurements from the Multi-Filter Rotating Shadowband Radiometer (MFRSR) at five wavelengths (415, 500, 615, 673, and 870 nm). These MFRSR data are collected at a coastal site in Graciosa Island, Azores supported by the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program. The areal-averaged albedos obtained from the MFRSR are compared with collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) whitesky albedo at four nominal wavelengths (470, 560, 670 and 860 nm). These comparisons are made during a 19-month period (June 2009 - December 2010). We also calculate composite-based spectral values of surface albedo by a weighted-average approach using estimated fractions of major surface types observed in an area surrounding this coastal site. Taken as a whole, these three methods of finding albedo show spectral and temporal similarities, and suggest that our simple, transmission-based technique holds promise, but with estimated errors of about ±0.03. Additional work is needed to reduce this uncertainty in areas with inhomogeneous surfaces.
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Evgueni Kassianov, Evgueni Kassianov, James Barnard, James Barnard, Connor Flynn, Connor Flynn, Laura Riihimaki, Laura Riihimaki, Cristina Marinovici, Cristina Marinovici, } "How well can we estimate areal-averaged spectral surface albedo from ground-based transmission in the Atlantic coastal area?", Proc. SPIE 9640, Remote Sensing of Clouds and the Atmosphere XX, 96400K (16 October 2015); doi: 10.1117/12.2196875; https://doi.org/10.1117/12.2196875
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