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首页> 外文会议>Ninth Joint International Symposium on Atmospheric and Ocean Optics/Atmospheric Physics. Part I: Radiation Propagation in the Atmosphere and Ocean Jul 2-5, 2002 Tomsk, Russia >Backscattering radiance calculation in a turbid medium with anisotropic scattering by spherical harmonics method
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Backscattering radiance calculation in a turbid medium with anisotropic scattering by spherical harmonics method

机译：利用球谐函数法计算各向异性散射的混浊介质的背向散射辐射

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摘要

In actual mediums with anisotropic scattering (atmospheric aerosol or marine water) in small angle approximation (SA) is possible simply and accurately to calculate light field radiance in forward from a source directions. The backscattering calculation in these mediums by any known method is complex and has no sufficient precision for practical problems: spherical harmonics (SH) method (taking into account the eliminating of direct component) has strong oscillation, Monte-Carlo method has a large variance, concerned with improbable event with large weight, and the first iteration from SA has uncontrollable precision and validity range. In suggested solution the refinement of SA is found by SH method. The SA solution is taken in small angle modification of SH method. This allows receiving analytical solution in the form of an exponential of matrix. Last circumstance requires numerical calculation under the obtained expression, however in the most unfavorable case the amount of terms in the refinement does not exceed 21 harmonics. The solution is practically smooth at any sharpness of a scattering phase function. Calculation time on the obtained algorithm is almost equivalent to time of calculation on SA. In addition, algorithm allows improving radiance distributions in a forward hemisphere.
机译：在具有各向异性散射的实际介质（大气气溶胶或海水）中，可以简单而准确地以小角度近似（SA）计算从光源方向向前的光场辐射。用任何已知方法在这些介质中进行的反向散射计算都很复杂，并且对实际问题没有足够的精度：球形谐波（SH）方法（考虑到消除了直接成分）的振荡很强，蒙特卡洛方法的方差大， SA涉及的重大事件不太可能发生，而SA的第一次迭代具有不可控制的精度和有效范围。在建议的解决方案中，通过SH方法发现了SA的细化。 SA解决方案采用SH方法的小角度修改。这允许接收矩阵指数形式的分析解。最后一种情况需要根据所获得的表达式进行数值计算，但是在最不利的情况下，细化中的项的数量不超过21次谐波。在任何散射相位函数的锐度下，该解决方案实际上都是平滑的。所获得的算法的计算时间几乎等于SA的计算时间。另外，算法允许改善前半球的辐射度分布。

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