Retrieval of aerosol components directly from satellite and ground-based measurements
Retrieval of aerosol components directly from satellite and ground-based measurements
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DOI：
10.5194/acp-19-13409-2019
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发表时间：
2019-11
影响因子：
6.3
通讯作者：
Lei Li;O. Dubovik;Y. Derimian;G. Schuster;Tatyana Lapyonok;P. Litvinov;F. Ducos;D. Fuertes;Cheng Chen;Zhengqiang Li;A. Lopatin;B. Torres;H. Che
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文献类型：
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作者：
Lei Li;O. Dubovik;Y. Derimian;G. Schuster;Tatyana Lapyonok;P. Litvinov;F. Ducos;D. Fuertes;Cheng Chen;Zhengqiang Li;A. Lopatin;B. Torres;H. Che
抽象的。这项研究提出了一种在大空间和时间域上远程监测气溶胶成分的新颖方法。该概念在 GRASP（气溶胶和表面属性的广义检索）算法中实现，可根据测量的辐射率直接推断气溶胶成分。假设观察到的气溶胶是嵌入黑碳、棕碳、氧化铁和其他（非吸收性）不溶性夹杂物的水合可溶性颗粒的混合物。干燥组分的复折射率是先验固定的（尽管可溶主体的折射率允许随水合而变化），并且混合物的复折射率是使用混合规则计算的。这些成分的体积分数与尺寸分布和球形颗粒的分数以及卫星数据反演时的光谱表面反射率一起得出。检索是作为连续解决方案空间中的统计优化拟合来实现的。这与大多数传统方法形成鲜明对比，在大多数传统方法中，气溶胶的类型要么与一组查找表中包含的预先假定的气溶胶模型相关，要么通过对检索到的气溶胶光学参数（例如，由 AERONET 检索算法提供的单散射反照率、折射率等）的分析来确定；在这里，我们显式检索气溶胶成分。该方法还直接连接到全球化学品运输模型中使用的数量。我们首先用合成数据测试了该方法以估计不确定性，然后将其应用于真实的地基 AERONET 和星载 POLDER/PARASOL 观测；因此，该研究首次尝试从与全球化学品迁移模型数量相关的卫星观测中获取气溶胶成分。我们的结果表明，气溶胶光学特性与标准产品高度一致（例如，气溶胶光学厚度的 R 约为 0.9），并证明了分离细颗粒和粗颗粒气溶胶的固有光学特性的能力。我们将我们的方法应用于全球范围内的 POLDER/PARASOL 辐射，并获得了气溶胶成分的空间和时间模式，这与气溶胶来源和传输特征的现有知识非常吻合。最后，我们讨论了这项新技术的局限性和前景。
Abstract. This study presents a novel methodology for the remote monitoring of aerosol components over large spatial and temporal domains. The concept is realized within the GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm to directly infer aerosol components from the measured radiances. The observed aerosols are assumed to be mixtures of hydrated soluble particles embedded with black carbon, brown carbon, iron oxide, and other (non-absorbing) insoluble inclusions. The complex refractive indices of the dry components are fixed a priori (although the refractive index of the soluble host is allowed to vary with hydration), and the complex refractive indices of the mixture are computed using mixing rules. The volume fractions of these components are derived along with the size distribution and the fraction of spherical particles, as well as the spectral surface reflectance in cases when the satellite data are inverted. The retrieval is implemented as a statistically optimized fit in a continuous space of solutions. This contrasts with most conventional approaches in which the type of aerosol is either associated with a pre-assumed aerosol model that is included in a set of look-up tables, or determined from the analysis of the retrieved aerosol optical parameters (e.g., single scattering albedo, refractive index, among others, provided by the AERONET retrieval algorithm); here, we retrieve the aerosol components explicitly. The approach also bridges directly to the quantities used in global chemical transport models. We first tested the approach with synthetic data to estimate the uncertainty, and then applied it to real ground-based AERONET and spaceborne POLDER/PARASOL observations; thus, the study presents a first attempt to derive aerosol components from satellite observations specifically tied to global chemical transport model quantities. Our results indicate aerosol optical characteristics that are highly consistent with standard products (e.g., R of ∼0.9 for aerosol optical thickness) and demonstrate an ability to separate intrinsic optical properties of fine- and coarse-sized aerosols. We applied our method to POLDER/PARASOL radiances on the global scale and obtained spatial and temporal patterns of the aerosol components that agree well with existing knowledge on aerosol sources and transport features. Finally, we discuss limitations and perspectives of this new technique.