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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0.532μm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。
Using lidar to detect the physical properties of water cloud, depolarization information will appear in the radar echo signal, which is caused by the multiple scattering of the laser and the clouds. The depolarization information can be used to invert the cloud characteristics. The semi-analytical Monte Carlo method was used to study the sensitivity of the back-scatter depolarization ratio at a wavelength of 0.532 μm to the cloud bottom height, droplet size and extinction coefficient. The calculated results show that the higher the depolarization ratio is, the greater the extinction coefficient is and the larger the depolarization ratio is for the same receiving field angle. The larger the receiving angle of view of the radar, the receiver captures The more scattering information, the greater the depolarization ratio. When the penetration depth is small, the cloud depolarization ratio is smaller with smaller droplet size. With the increase of penetration depth, cloud depolarization ratio with larger droplet size is larger.