考虑多次散射影响的斜程能见度反演方法研究

提出了一种在低能见度天气条件下考虑多次散射影响时激光雷达反演斜程能见度的组合算法。首先,根据Koschmieder定律构建能见度方程,确定斜程能见度与大气光学厚度的依赖关系;其次,根据多次散射激光雷达方程采用双仰角法反演大气光学厚度,并采用半解析Monte Carlo法计算多次散射对单次散射比值;最后,求出考虑多次散射影响时的斜程能见度。使用地基激光雷达垂直探测进行斜程分解的回波信号数据,进行了实验验证。结果表明,在能见度小于1km时,考虑与未考虑多次散射影响的斜程能见度相对误差达9%,并且随着能见度的降低,多次散射对单次散射比值逐渐增大,多次散射作用增强。因此,研究低能见度天气条件下,多次散射的影响是非常必要的。

Slant-range visibility retrieve considering multiple scattering effects

A hybrid algorithm for determining the slant - range visibility using lidar data in the low - visibility atmosphere is proposed,considering mu ltiple - scattering effects.In the algorithm,the mathematical relation of the slant - range visibility and the atmospheric optical depth is firstly deduced according to Koschmieder law.Secondly, the optical depth is derived from the multiple - scattering lidar equ ation,taking advantages of multi - elevation angles. Meanwhile,the ratio of scattering coefficient for multiple scattering to that f or single scattering is calculated by semi - analytic Monte Carlo method.In the end,the slant - range visibility is obtained,wi th the consideration of multiple - scattering effects.The proposed algorithm has been used for retrieving the slan t - range visibility from returns of a ground - based lidar operating in vertical detection status.The results show that the re lative error of the obtained slant - range visibility with and without considering the multiple - scattering effects is up to 9%.It is noted that the multiple - scattering effects may become more significant as the visibility decreases.This is demonstrated by the increase of the ratio of scattering coefficient for multiple scattering to that for single scatt ering.Therefore, in order to accurately retrieve the slant - range visibility using lidar data,the multiple - scattering effects have to be considered,especially for the condit ion of low -visibility atmosphere.