Abstract
Tower-based data combined with high-resolution satellite products have been used to produce surface albedo at various spatial scales over land. Because tower-based albedo data are available at only a few sites, surface albedos using these combined data are spatially limited. Moreover, tower-based albedo data are not representative of highly heterogeneous regions. To produce areal-averaged and spectrally-resolved surface albedo for regions with various degrees of surface heterogeneity, we have developed a transmission-based retrieval and demonstrated its feasibility for relatively homogeneous land surfaces. Here, we demonstrate its feasibility for a highly heterogeneous coastal region. We use the atmospheric transmission measured during a 19-month period (June 2009–December 2010) by a ground-based Multi-Filter Rotating Shadowband Radiometer (MFRSR) at five wavelengths (0.415, 0.5, 0.615, 0.673 and 0.87 µm) at the Department of Energy’s Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) site located on Graciosa Island. We compare the MFRSR-retrieved areal-averaged surface albedo with albedo derived from Moderate Resolution Imaging Spectroradiometer (MODIS) observations, and also a composite-based albedo. We demonstrate that these three methods produce similar spectral signatures of surface albedo; however, the MFRSR-retrieved albedo, is higher on average (≤0.04) than the MODIS-based areal-averaged surface albedo and the largest difference occurs in winter.
Highlights
Knowing that surface albedo substantially affects the variability of the Earth’s radiation balance [1], and that this variability is sensitive to multiple natural and man-made factors [2], the importance of monitoring the surface albedo from ground, air and space [3,4,5,6,7] is increasingly recognized.The assessment of these variations is challenging for heterogeneous regions where complex landscapes with distinctive land cover types occur
Moderate Resolution Imaging Spectroradiometer (MODIS) observations, and a composite-based albedo. We demonstrate that these three methods produce similar spectral signatures of surface albedo; the Multi-Filter Rotating Shadowband Radiometer (MFRSR)-retrieved albedo, is higher on average (≤0.04) than the MODIS-based areal-averaged surface albedo and the largest difference occurs in winter
We have demonstrated good agreement between the spectrally-resolved values of surface albedo retrieved by our MFRSR-based approach and those measured by towers and derived from Moderate Resolution Imaging Spectroradiometer (MODIS) observations for relatively homogeneous surfaces in the Southern Great Plains of North
Summary
Knowing that surface albedo substantially affects the variability of the Earth’s radiation balance [1], and that this variability is sensitive to multiple natural and man-made factors [2], the importance of monitoring the surface albedo from ground, air and space [3,4,5,6,7] is increasingly recognized The assessment of these variations is challenging for heterogeneous regions where complex landscapes with distinctive land cover types occur. We illustrate the performance of our retrieval for a coastal region with a highly heterogeneous surface (including land and ocean) and compare the MFRSR-retrieved values of the areal-averaged albedo with those obtained by two conventional approaches based on high resolution satellite images and MODIS data. The main objective of our comparison is to illustrate the level of agreement between the areal-averaged albedos provided by three methods under these challenging observational conditions rather than documenting the superiority of one of these three methods
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