物理学报2019，Vol.68Issue(4)：184-199,16.DOI:10.7498/aps.68.20181682
高分五号卫星多角度偏振相机最优化估计反演:角度依赖与后验误差分析
Optimal estimation retrieval for directional polarimetric camera onboard Chinese Gaofen-5 satellite: an analysis on multi-angle dependence and a posteriori error
摘要
Abstract
Data from the directional polarimetric camera (DPC) instrument onboard Chinese Gaofen-5 satellite dedicated to aerosol monitoring have been available recently. By measuring the spectral, angular and polarization properties of the radiance at the top of atmosphere (TOA), a DPC provides the aerosol optical depths (AODs) as well as partial microphysical aerosol properties. In order to evaluate the capability and the retrieval uncertainty of DPC sensor systematically, the information content and a posteriori error analysis are applied to the synthetic data of DPC multi-angle observation in this paper, which inherits from the optimal estimate theoretical framework. The forward simulation is conducted by the unified linearized vector radiative transfer model (UNL-VRTM), and the Jacobians of four Stokes elements with respect to aerosol and surface model parameters can be obtained simultaneously. Firstly, the error influences of surface parameter on the TOA measurements are simulated. The results indicate that a 10％ relative error of parameter k1 in the improved BRDF model results in about 4.65％ error of the TOA reflectance, while the error of TOA polarized reflectance caused by the same error of parameter C in BPDF model is negligibly small. Secondly, the multi-angle dependence of total information content in DPC measurements is investigated. It is shown that the information content increases significantly with the number of viewing angles, especially for the measurements of the first 9 angles. The DPC multi-angle observation can provide extra 5 degrees of freedom for signal (DFS) for the retrieval of aerosol and surface parameters, in which the retrieval of aerosol parameters is more sensitive to observation geometries than the retrieval of surface parameters in most cases. In addition, the total aerosol DFS increases with the range extension of scattering angle under the same number of viewing angles. After that, the DFS of each retrieved aerosol and surface parameter are given. For the aerosols, the volume concentration, realpart refractive index and effective radius show a high DFS (greater than 0.8). For the surfaces, the mean DFS of each parameter is greater than 0.5, which indicates the well capability of DPC in the surface retrieval. Finally, the a posteriori error of each aerosol, surface parameter and corresponding vary with the number of viewing angles, and the observation error and aerosol model error are discussed. The a posteriori error decrease significantly with the number of viewing angles, and the influence of the aerosol model error on the a posteriori error is not remarkable. In general, the observation error is the main influence factor on the uncertainty of the inversion results.关键词
多角度偏振相机/最优化估计反演/信息量分析/后验误差Key words
directional polarimetric camera/optimal estimation inversion/information content analysis/a posteriori error引用本文复制引用
郑逢勋,侯伟真,李正强..高分五号卫星多角度偏振相机最优化估计反演:角度依赖与后验误差分析[J].物理学报,2019,68(4):184-199,16.基金项目
国家重点研发计划(批准号: 2016YFE0201400)、中国科学院科技服务网络计划(STS) 区域重点项目(批准号: KFJ-STS-QYZD-022)、遥感科学国家重点实验室开放基金(批准号: OFSLRSS201710) 和国家自然科学基金(批准号: 41671367, 41505022, 41871269) 资助的课题. （批准号: 2016YFE0201400）
