激光雷达探测水云退偏振比的敏感性研究

利用激光雷达探测水云微物理特性时，雷达回波信号中会出现退偏振信息，这是由激光与云层的多次散射造成的，利用这些退偏振信息可以反演云层特性。利用半解析蒙特卡罗方法研究了波长为0.532m激光雷达后向散射退偏振比对云底高度、云滴大小以及消光系数的敏感性。计算结果表明，对于相同的接收视场角，激光雷达与云层的距离越远，退偏振比越高；消光系数越大，退偏振比越大；雷达接收视场角越大，被接收器捕获的多次散射信息越多，因此退偏振比越大。当穿透深度较小时，云滴尺寸较小的云层退偏比更高，随着穿透深度的增加，云滴尺寸更大的云层退偏振比更大。

Sensitivity study on lidar detection of the depolarization ratio of water clouds

The polarization lidar returns exist a depolarization signal due to the occurrence of multiple scattering when detecting the microphysics characteristics of liquid water clouds by using lidar. The depolarization information can be used to quantitatively retrieve the clouds characteristics. The semi-analytic Monte Carlo simulation was used to study the backscattering depolarization ratio of polarization lidar with the wavelength of 0.532 m to the height of clouds base, size of the clouds droplets and the extinction coefficient. From the results, if the receiving angle of field remains constant, the depolarization ratio increases with the increase of the distance between the lidar and the clouds and the increase of the extinction coefficients. The impacts of multiple scattering increase with the increase of the receiver field of view angles, so a bigger receiver field of the angle will generate a bigger depolarization ratio. The depolarization ratio is bigger for the clouds with a smaller clouds droplets when the penetration depth is small, but it will be bigger for the clouds with a bigger clouds droplets when the penetration depth is more deeply.