Allen R J, Platt C M
Appl Opt. 1977 Dec 1;16(12):3193-9. doi: 10.1364/AO.16.003193.
A lidar system that can measure multiple scattering and depolarization in the atmosphere is being used to study the climatic effects of cirrus clouds and to perform other investigations. The lidar system and its novel aspects are described in this paper. The influence of multiple scattering on noise, signal, and SNR is considered. Special receiver field stops incorporated for multiple scattering measurements, use of low voltage to control the photomultiplier tube gain, and a precision power/energy monitor are described. A technique for aligning transmitter and receiver axes and measuring transmitter beamwidth is presented. The multiple-scattered components of backscattered light are determined by inserting a center-blocked field stop to restrict the receiver field of view to the region outside of the diverging transmitted beam. Typical returns with and without the opaque field stop indicate the amplitude of multiple scattering from cirrus clouds and prove the feasibility of this technique. The depolarization ratio delta and backscatter coefficients from an altostratus cloud illustrate the potential of these quantities for the study of cloud structure and phase.
一种能够测量大气中多次散射和去极化的激光雷达系统正被用于研究卷云的气候效应以及进行其他调查。本文描述了该激光雷达系统及其新颖之处。考虑了多次散射对噪声、信号和信噪比的影响。介绍了为多次散射测量而并入的特殊接收器视场光阑、使用低电压控制光电倍增管增益以及一种精密功率/能量监测器。提出了一种对准发射机和接收机轴以及测量发射机波束宽度的技术。通过插入一个中心遮挡的视场光阑将接收器视场限制在发散发射光束之外的区域，来确定后向散射光的多次散射分量。有无不透明视场光阑时的典型回波表明了卷云多次散射的幅度，并证明了该技术的可行性。高层云的去极化率δ和后向散射系数说明了这些量在研究云结构和相态方面的潜力。
