Global aerosol optical properties and application to Moderate Resolution Imaging Spectroradiometer aerosol retrieval over land
Global aerosol optical properties and application to Moderate Resolution Imaging Spectroradiometer aerosol retrieval over land
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DOI：
10.1029/2006jd007815
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发表时间：
2007-07-13
影响因子：
4.4
通讯作者：
Dubovik, Oleg
中科院分区：
文献类型：
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作者：
Levy, Robert C.;Remer, Lorraine A.;Dubovik, Oleg
随着从遥感反演和现场测量中获得更多有关全球气溶胶特性的信息，谨慎的做法是对这些新信息本身以及在卫星反演算法的背景下进行评估。利用全球气溶胶观测网（AERONET）太阳光度计站点的高度角扫描反演的气候学资料，我们进行聚类分析以确定气溶胶类型随位置和季节的变化。我们发现三种源自球形的类型（描述以细粒子为主的气溶胶）和一种源自椭球形的类型（描述以粗粒子为主的气溶胶，可能是沙尘）大致描述了AERONET所观测到的全球气溶胶特性的范围。以细粒子为主的类型主要根据其单次散射反照率（ω₀）来区分，在发达的城市/工业地区为非吸收性气溶胶（ω₀约为0.95），在森林火灾燃烧和发展中的工业地区为中等吸收性气溶胶（ω₀约为0.90），在热带稀树草原/草原燃烧地区为吸收性气溶胶（ω₀约为0.85）。我们确定了每个站点的主要气溶胶类型，并外推创建了预期气溶胶类型的季节性1°×1°地图。每种气溶胶类型都是双对数正态分布的，具有动态的（随光学厚度变化的）尺度参数（半径、标准差、体积分布）和复折射率。这些参数不仅本身很有趣，还可应用于气溶胶反演算法，例如用于中分辨率成像光谱仪在陆地上的气溶胶反演。AERONET对光谱气溶胶光学厚度（τ）的独立的直接太阳观测与模型的光谱依赖性是一致的，这表明我们推导出的气溶胶模型是相关的。
As more information about global aerosol properties has become available from remotely sensed retrievals and in situ measurements, it is prudent to evaluate this new information, both on its own and in the context of satellite retrieval algorithms. Using the climatology of almucantur retrievals from global Aerosol Robotic Network (AERONET) Sun photometer sites, we perform cluster analysis to determine aerosol type as a function of location and season. We find that three spherical-derived types (describing fine-sized dominated aerosol) and one spheroid-derived types (describing coarse-sized dominated aerosol, presumably dust) generally describe the range of AERONET observed global aerosol properties. The fine-dominated types are separated mainly by their single scattering albedo (omega(0)), ranging from nonabsorbing aerosol (omega(0)similar to 0.95) in developed urban/industrial regions, to moderately absorbing aerosol (omega(0)similar to 0.90) in forest fire burning and developing industrial regions, to absorbing aerosol (omega(0)similar to 0.85) in regions of savanna/grassland burning. We identify the dominant aerosol type at each site, and extrapolate to create seasonal 1 degrees x1 degrees maps of expected aerosol types. Each aerosol type is bilognormal, with dynamic (function of optical depth) size parameters (radius, standard deviation, volume distribution) and complex refractive index. Not only are these parameters interesting in their own right, they can also be applied to aerosol retrieval algorithms, such as to aerosol retrieval over land from Moderate Resolution Imaging Spectroradiometer. Independent direct-Sun AERONET observations of spectral aerosol optical depth (tau) are consistent the spectral dependence of the models, indicating that our derived aerosol models are relevant.