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

Abstract Forest background reflectivities with seasonal and spatial variations are critically important in the estimation of canopy biophysical parameters of the forest canopy. In this paper, seasonal background reflectivity for global forested areas was mapped at 1.1 km resolution using four‐scale model and Multi‐angle Imaging Spectroradiometer data of the nadir and 45° forward directions. The largest seasonal variation of forest background reflectivities was observed in middle and high latitudes of Northern Hemisphere. The background reflectivity differs between deciduous broadleaf forest and coniferous forest in the near‐infrared band and varies with increasing canopy leaf area index. The partial validation of forest background reflectivity with adjacent grassland in the Northern Hemisphere and the comparison of understory leaf area index on leaf appearance day for larch forest 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 global coniferous and deciduous broadleaf forest areas. Key Points The first global seasonal understory reflectivity maps Mapping understory reflectivity with MISR data Help to model contributions of forest and understory vegetation in ecosystem