Optical Attenuation in Clouds from Inversion of Multi-Wave-Length and Multi-Angle Lidar Data

摘要

The purpose of this study was to determine if optical attenuation in clouds could be accurately determined solely by inverting multi-wavelength and multi-angle lidar data by means of the Backus-Gilbert inversion technique. This is an indirect method to attain the attenuation coefficient as the Backus-Gilbert inversion provides an estimate of the cloud droplet size distribution, and from this distribution the attenuation coefficient might then be calculated. This study directed its attention to a more narrow range of scattering angles. Specifically, there is a requirement to measure optical attenuation from naval ships so that bistatic lidar configuration would be limited by the dimensions of the vessel carrying the equipment. Although other methods of inverting lidar returns may yield 'better' results than Backus-Gilbert, this inversion technique permits one to investigate the information content of the measurements being made. Visually displaying the averaging kernels also helps indicate where and why errors in the results occur, and defines over what size interval the retrieved number density is applicable.