Mapping global seasonal forest background reflectivity with Multi-angle Imaging Spectroradiometer data

China 973 program 2010CB950701；National Natural Science Foundation of China 41171285；Estonian Science Foundation PUT232<p class="FR_field"> <span class="hitHilite">Forest</span> <span class="hitHilite">background</span> reflectivities with <span class="hitHilite">seasonal</span> and spatial variations are critically important in the estimation of canopy biophysical parameters of the <span class="hitHilite">forest</span> canopy. In this paper, <span class="hitHilite">seasonal</span> <span class="hitHilite">background</span> reflectivity for <span class="hitHilite">global</span> forested areas was mapped at 1.1 km resolution using four-scale model and Multi-angle Imaging Spectroradiometer data of the nadir and 45 degrees forward directions. The largest <span class="hitHilite">seasonal</span> variation of <span class="hitHilite">forest</span> <span class="hitHilite">background</span> reflectivities was observed in middle and high latitudes of Northern Hemisphere. The <span class="hitHilite">background</span> reflectivity differs between deciduous broadleaf <span class="hitHilite">forest</span> and coniferous <span class="hitHilite">forest</span> in the near-infrared band and varies with increasing canopy leaf area index. The partial validation of <span class="hitHilite">forest</span> <span class="hitHilite">background</span> reflectivity with adjacent grassland in the Northern Hemisphere and the comparison of understory leaf area index on leaf appearance day for larch <span class="hitHilite">forest</span> in North Asia both indicate the relative reliability of results. The nearly 70% spatial coverage of retrieval with high-quality flags makes it eligible for applications over <span class="hitHilite">global</span> coniferous and deciduous broadleaf <span class="hitHilite">forest</span> areas.