首页 >  2009, Vol. 13, Issue (5) : 771-784

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引用本文:

DOI:

10.11834/jrs.20090501

收稿日期:

2008-05-16

修改日期:

2009-01-13

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多次散射对向上漫射散射系数及漫射吸收系数影响的数值研究
1.南京信息工程大学 遥感学院, 江苏 南京 210044;2.南京信息工程大学 环境科学与工程学院, 江苏 南京 210044
摘要:

在假定水体表面为镜面、水体中无内光源及非弹性散射的情况下、利用多次散射理论, 研究了在固定体散射函数的情况下, 不同的入射天顶角、单次散射反照率和散射系数对向上漫射散射系数, 上、下行漫射吸收系数的影响。结果表明: 在紧贴水表的下层, 向上漫射散射系数随入射辐射天顶角的增大而增大, 但不随单次散射反照率和散射系数的改变而改变; 当入射辐射为垂直入射时, 向上漫射散射系数的深度廓线随深度呈现单调增的趋势, 并逐步接近一个恒定状态; 随着入射天顶角的增大, 该单调现象发生了变化, 出现先增大后减小, 再逼进恒定状态, 且这个恒定值随单次反照率增大而增大。下行漫射吸收系数随着入射天顶角的增大, 其廓线由单调增加过渡到先增大后减小; 在散射系数和单次散射反照率相同的条件下, 不同入射天顶角的下行漫射吸收系数逐渐收敛于同一稳定的状态。且单次散射率越小, 这种收敛的速度越快, 达到恒定状态的深度也越浅。上行漫射吸收系数的主要特征基本与下行漫射吸收系数类似, 而且两个恒定值均大于属于固有光学参数的吸收系数, 其中向上漫射吸收系数最大。

Numerical study on the effect of multiple scattering on upward scattering coefficients and diffuse absorption coefficients of medium in water
Abstract:

Upward scattering coefficients and diffuse absorption for the down- and up-welling streams are key factors for remote sensing of waters, and the interaction between biology and optics. They are also important parameters of underwater light fields. On the assumption that the radiance field has no internal light source, no inelastic scattering and the water surface was flat, we studied the effects of the zenith of incident, albedo and scattering coefficient on upward scattering coefficient, diffuse absorption coefficient for the downwelling and upwelling streams on condition that a scattering phase function was selected. The upward scattering coefficient showed an increase with the zenith of incident increasing, but the coefficient did not change along with the albedo and scattering coefficient just below water surface. With depth increasing, the profile of upward scattering coefficients gradually approached a constant, and the constant increased with albedo increasing. The profile of upward scattering coefficients strictly increased and then gradually approached a constant with depth increasing when the incidence was normal to the water surface. With further enhancement of zenith angle, the profile gradually increased, then decreased, hereafter kept invariable; while the invariant value increased with albedo increasing, but did not change with zenith angle of incident. The profiles of diffuse absorption coefficients for downwelling streams gradually shifted from strictly increase and followed stability to the new trend which took on first increase and next decrease, then to a constant state. Given that scattering coefficient and albedo was the same, the diffuse absorption coefficients for downwelling streams of different incident zenith converged to stability gradually. The less the albedo was, the more rapid convergent rate was, the shallower the depth of approaching to asymptotic state was. The characteristics of diffuse absorption coefficient for upwelling streams were very similar to that of diffuse absorption coefficient for downwelling streams, the former was merely bigger than the latter, and the diffuse absorption coefficients for upwelling streams were the maximum among them.

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