15 December 1995 Sensitivity of the earth-atmosphere bidirectional reflectivity functions to variations in cloud parameters
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Abstract
The study of the Earth radiation budget is important for understanding the long-term impact of industrialization on the environment. Clouds exert the single most important influence on the Earth radiation budget. The ideal situation for predicting the effect of clouds is to have one of two extremes: either a cloud-free sky or a completely overcast sky. Each of these cases can easily be treated with a simple one-dimensional model. However, the more usual partly-cloudy sky condition introduces the possibility of an unlimited variety of cloud geometries, size and spatial distributions, and properties. In most of these cases the interaction among neighboring clouds presents a set of problems which cannot be accurately simulated with plane-parallel or even two-dimensional models. Only in recent years have researchers begun to understand the relationships between cloud three-dimensional effects and the anisotropy of Earth-reflected radiance. In the real world, the influence of clouds on radiation depends not only on liquid water content, or optical depth, but also on cloud microphysical properties such as particle shape, size distribution, and on cloud morphology and spatial distribution (Parol, et al., 1994). As shown by Stevens and Greenwald (1991), cloud morphology is likely to have a larger impact on the Earth radiation budget than cloud microphysics. Thus, it is very important to quantify and parameterize the influence of cloud inhomogeneities on the radiation field. The anisotropy of any radiation field can be studied by normalizing the emitted or reflected radiance by the equivalent Lambertian directional distribution of energy leaving the field. The work in this paper deals entirely with the shortwave portion of the spectrum; longwave emitted energy is not treated.
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Pierre V. Villeneuve, J. Robert Mahan, "Sensitivity of the earth-atmosphere bidirectional reflectivity functions to variations in cloud parameters", Proc. SPIE 2582, Atmospheric Sensing and Modeling II, (15 December 1995); doi: 10.1117/12.228533; https://doi.org/10.1117/12.228533
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