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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >A MODIFIED LINEAR-MIXING METHOD FOR CALCULATING ATMOSPHERIC PATH RADIANCES OF AEROSOL MIXTURES
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A MODIFIED LINEAR-MIXING METHOD FOR CALCULATING ATMOSPHERIC PATH RADIANCES OF AEROSOL MIXTURES

机译：一种修正的线性混合法计算气溶胶混合物的大气路径半径

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The top-of-atmosphere (TOA) path radiance generated by an aerosol mixture can be synthesized by linearly adding the contributions of the individual aerosol components, weighted by their fractional optical depths. The method, known as linear mixing, is exact in the single-scattering limit. When multiple scattering is significant, the method reproduces the atmospheric path radiance of the mixture with <3% errors for weakly absorbing aerosols up to optical thickness of 0.5. However, when strongly absorbing aerosols are included in the mixture, the errors are much larger. This is due to neglecting the effect of multiple interactions between the aerosol components, especially when the values of the single-scattering albedos of these components are so different that the parameter epsilon = Sigma f(i)pi(i) - pi(mix)/pi(i) is larger than similar to 0.1, where pi(i) and f(i) are the single-scattering albedo and the fractional abundance of the ith component, and pi(mix) is the effective single-scattering albedo of the mixture. We describe an empirical, modified linear-mixing method which effectively accounts for the multiple interactions between aerosol components. The modified and standard methods are identical when epsilon = 0.0 and give similar results when epsilon less than or equal to 0.05. For optical depths larger than similar to 0.5, or when epsilon > 0.05, only the modified method can reproduce the radiances within 5% error for common aerosol types up to optical thickness of 2.0. Because this method facilitates efficient and accurate atmospheric path radiance calculations for mixtures of a wide variety of aerosol types, it will be used as part of the aerosol retrieval methodology for the Earth Observing System (EOS) multiangle imaging spectroradiometer (MISR), scheduled for launch into polar orbit in 1998. [References: 6]
机译：可以通过线性添加各个气溶胶成分的贡献（由其分数光学深度加权）来合成由气溶胶混合物产生的大气顶（TOA）路径辐射。该方法被称为线性混合，在单散射极限内是精确的。当多次散射很明显时，该方法以小于3％的误差再现混合物的大气路径辐射，从而弱吸收气溶胶直至光学厚度为0.5。但是，当混合物中包含强烈吸收的气溶胶时，误差会更大。这是由于忽略了气溶胶成分之间的多重相互作用的影响，尤其是当这些成分的单散射反照率的值如此不同以至于参数epsilon = Sigma f（i） pi（i）-pi（mix ） / pi（i）大于0.1，其中pi（i）和f（i）是单散射反照率和ith分量的分数丰度，而pi（mix）是有效的单散射混合物的反照率。我们描述了一种经验的，改进的线性混合方法，该方法有效地解决了气溶胶成分之间的多重相互作用。当epsilon = 0.0时，修改后的方法和标准方法相同，而当epsilon小于或等于0.05时，得出的结果相似。对于大于约0.5的光学深度，或者当epsilon> 0.05时，对于最大厚度为2.0的常见气溶胶类型，只有改进的方法才能在5％误差范围内重现辐射。因为此方法有助于对各种气溶胶类型的混合物进行有效且准确的大气路径辐射率计算，所以它将用作计划用于发射的地球观测系统（EOS）多角度成像光谱仪（MISR）的气溶胶检索方法的一部分在1998年进入极轨道。[参考：6]

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