Different from the principal component analysis (PCA), non-negative matrix factorization (NMF) can provide more direct interpretation owning to the non-subtractive combinations of non-negative basis vectors, and many practical problems also require non-negative basis vectors rather than the orthogonal vectors with alternating positive and negative. In this study, we develop a hyperspectral surface reflectance reconstruction method based on NMF and multispectral results in several wavelength bands. In order to test our spectral reconstruction method, the spectral datasets of typical surface types are extracted from the spectral library of John Hopkins University (JHU), which include the soil, vegetation, manmade materials, sedimentary fine and coarse rock. The prior surface reflectance or emissivity results are selected from only four wavelength bands (2.13, 3.75, 3.96, 4.05 μm) from shortwave infrared to Mid-infrared, which can be easily obtained from the surface product of Moderate-resolution Imaging Spectroradiometer (MODIS). Based on the JHU spectral dataset and NMF, the hyperspectral surface reflectance in the spectral range of 2-5μm with the step of 25 nm can be reconstructed consistently. In addition, the hyperspectral reconstruction effects by NMF are quantitatively investigated, in which the root mean square error and the mean absolute error is about 0.016 and 0.01, respectively.
For the satellite remote sensing of aerosols in Ultraviolet (UV) wavelength bands, the atmospheric widow in UVA spectral bands from 315nm to 400nm are usually used. To derive the aerosols and surface reflectance from satellite UV measurements, a suitable radiative transfer model is indispensable for designed retrieval algorithms. In this study, we focus on the sensitivity study of polarization measurements in the UV wavelength bands, and Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) is used as the forward model for the simulation of the synthetic data. The hyperspectral surface reflectance of green vegetation and man-made materialsin UV have been extracted from the spectral library of John Hopkins University (JHU), and the polarized surface reflectance is also integrated in forward simulations. Both the fine-mode and coarse mode dominated aerosols are selected to investigate the influence on the measurements at the top of the atmosphere (TOA). For the separate contributions of Rayleigh scattering, aerosols scattering/absorption and surface-atmosphere coupled results, different input options are set in the UNL-VRTM. With the combination of gas absorption in forward simulation, the Rayleigh contribution, atmospheric path radiance and coupled contribution with surface are obtained, and the corresponding sensitivities are investigated and discussed. The results in this study can provide important support for the design of retrieval algorithms in UV.
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