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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements
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A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements

机译：一种灵活的反演算法，可从太阳和天空的辐射度测量值中检索气溶胶的光学特性

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The problem of deriving a complete set of aerosol optical properties from Sun and sky radiance measurements is discussed. Algorithm development is focused on improving aerosol retrievals by means of including a detailed statistical optimization of the influence of noise in the inversion procedure. The methodological aspects of such an optimization are discussed in detail and revised according to both modern findings in inversion theory and practical experience in remote sensing. Accordingly, the proposed inversion algorithm is built on the principles of statistical estimation: the spectral radiances and various a priori constraints on aerosol characteristics are considered as multisource data that are known with predetermined accuracy. The inversion is designed as a search for the best fit of all input data by a theoretical model that takes into account the different levels of accuracy of the fitted data. The algorithm allows a choice of normal or lognormal noise assumptions. The multivariable fitting is implemented by a stable numerical procedure combining matrix inversion and univariant relaxation. The theoretical inversion scheme has been realized in the advanced algorithm retrieving aerosol size distribution together with complex refractive index from the spectral measurements of direct and diffuse radiation. The aerosol particles are modeled as homogeneous spheres. The atmospheric radiative transfer modeling is implemented with well-established publicly available radiative transfer codes. The retrieved refractive indices can be wavelength dependent; however, the extended smoothness constraints are applied to its spectral dependence (and indirectly through smoothness constraints on retrieved size distributions). The positive effects of statistical optimization on the retrieval results as well as the importance of applying a priori constraints are discussed in detail for the retrieval of both aerosol size distribution and complex refractive index. The developed algorithm is adapted for the retrieval of aerosol properties from measurements made by ground-based Sun-sky scanning radiometers used in the Aerosol Robotic Network (AERONET). The results of numerical tests together with examples of experimental data inversions are presented. [References: 64]
机译：讨论了从太阳和天空辐射度测量中得出完整的气溶胶光学特性的问题。算法开发的重点是通过在反演程序中包括对噪声影响的详细统计优化，从而改善气溶胶的获取。根据反演理论的现代发现和遥感实践经验，对这种优化的方法论方面进行了详细讨论和修订。因此，所提出的反演算法是建立在统计估计的原理之上的：光谱辐射和气溶胶特性的各种先验约束被认为是具有预定精度的多源数据。该反演旨在通过理论模型来搜索所有输入数据的最佳拟合，该模型考虑了拟合数据的不同精度级别。该算法允许选择正常或对数正态噪声假设。多变量拟合通过结合矩阵求逆和单变量松弛的稳定数值程序实现。在高级算法中已经实现了理论反演方案，该算法从直接辐射和漫射辐射的光谱测量值中检索了气溶胶尺寸分布以及复杂的折射率。气溶胶颗粒被建模为均匀球体。大气辐射传输建模是使用公认的公开可用的辐射传输代码实现的。取回的折射率可以与波长相关;但是，将扩展的平滑度约束应用于其频谱依赖性（并间接通过对检索到的大小分布的平滑度约束）。统计优化对检索结果的积极影响以及应用先验约束的重要性，对气溶胶粒径分布和复折射率的检索均进行了详细讨论。所开发的算法适用于从气溶胶机器人网络（AERONET）中使用的地面日照扫描辐射计进行的测量中检索气溶胶特性。介绍了数值测试的结果以及实验数据反演的示例。 [参考：64]

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