考虑多次散射的卷云几何特征和光学特性反演方法

研究了考虑多次散射的卷云几何特征和光学特性反演方法,对反演卷云高度和卷云激光雷达比的方法进行了改进。采用多次散射因子对卷云消光系数曲线进行修正,选取云底及云顶附近高度消光系数变化率的均值求解云层高度修正误差,对微分零交叉法求解得到的卷云高度进行修正,实现了较为精确的激光雷达云层高度反演。采用以边界值处消光系数和卷云光学厚度为约束条件的粒子群算法,求解卷云有效激光雷达比,选用半解析Monte Carlo方法,计算总散射信号与一次散射信号的比值,并结合Platt多次散射因子方程求得多次散射因子,实现了卷云激光雷达比的准确求解。使用Mie散射激光雷达真实回波信号进行了验证。结果表明,该改进方法具有较高的精度,更具应用价值。

A novel method of retrieving the geometrical and optical properties of cirrus cloud considering multiple scattering

The geometrical and optical properties of cirrus cloud with multiple scattering were studied and the retrieval methods of cirrus height and lidar ratio were improved. An approach was proposed for determining cirrus height based on multiple scattering factors and the extinction coefficients of cirrus were corrected by the factors. With multiple scattering factors and the extinction coefficients, the error of the cirrus-height was computed. Finally, the precise lidar cloud detection retrieval was achieved preliminarily. In the improved method of retrieving the lidar ratio with multiple scattering, the nonlinear equations with cirrus lidar ratio and cirrus extinction coefficient as variables were constructed, and the particle swarm optimization algorithm was used to solve the equations, the extinction coefficient of the cirrus's top and the lidar ratio of cirrus clouds were acquired. Then, through the PLATT's multiple scattering equation and the ratio of total scattering and signal scattering calculated by semi-analytic Monte Carlo method, the lidar ratio was obtained. The experiment was carried on based on the proposed method, using the real return signals of the ground-based lidar. It is turned out that the proposed technique has the advantages of high accuracy. Therefore, it has a promise future.