Linear unmixing of MODIS albedo composites to infer subpixel land cover type albedos |
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| Institution: | 1. Department of Forest Sciences, P.O. Box 27, 00014 University of Helsinki, Finland;2. The Finnish Forest Research Institute, P.O. Box 18, 01301 Vantaa, Finland;1. Key Laboratory of Alpine Ecology and Biodiversity, Institute of Tibetan Plateau Research of Chinese Academy of Sciences, Beijing 100101, China;2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;3. University of Chinese Academy of Sciences, Beijing 100039, China;4. College of Tourism and Territorial Resources, Jiujiang University, Jiujiang, Jiangxi 332005, China;1. Department of Science and Technology of Surveying and Mapping, College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China;2. Chinese Academy of Meteorological Sciences, Beijing 100081, China;3. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China;1. University of Copenhagen, Department of Geoscience and Natural Resource Management, Rolighedsvej 23, DK-1958 Frederiksberg C, Denmark;2. University of British Columbia, Department of Forest and Conservation Sciences, 2424 Main Mall, Vancouver V6T 1Z4, Canada;1. Shapotou Desert Research and Experiment Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China;;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. University of Oregon, United States;2. Federal Office of Meteorology and Climatology MeteoSwiss, Switzerland;3. Physikalisch-Meteorologisches Observatorium Davos World Radiation Center, Switzerland;1. Civil Protection Agency, Castilla y León Government, Valladolid, Spain;2. Agrarian Engineering and Sciences Department, University of León, Campus of Ponferrada, León, Spain;3. Electronic Technology Department, University of Valladolid, Spain;4. Sustainable Forest Management Research Institute, University of Valladolid-INIA, Spain |
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| Abstract: | We use a linear unmixing approach to test how land use and forestry maps, in combination with the MODIS BRDF/albedo product, can be used to estimate land cover type albedos in boreal regions. Operational land use maps from three test areas in Finland and Canada were used to test the method. The resulting endmember albedo estimates had low standard errors of the mean and were realistic for the main land cover types. The estimated albedos were fairly consistent with albedo measurements conducted with a telescope mast and pure pixel albedos. Problems with the method are the possible errors in the land cover maps, lack of good quality winter MODIS albedo composites and the mismatch between the MODIS pixels and the true observation area. The results emphasize the role of tree species as determinant of forest albedo. Comprehensive spatial and temporal measurements of land cover albedo are usually not possible with in situ mast measurements, and the spatial resolution of MODIS albedo product is often too low to allow direct comparison of pixel albedos and land cover types in areas with heterogeneous vegetation. Hence, and since local forestry maps exist for most temperate and boreal regions, we believe that the proposed method will be useful in estimating average regional land cover type albedos as well as in tracking changes in them. |
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| Keywords: | Albedo Boreal forest Linear unmixing MODIS BRDF/albedo |
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