基于Fizeau干涉仪的激光雷达测温方法研究

气温是描述大气状态的基本参数之一，温度的准确测量对天气预报、气候预测及其他气象参数的反演都至关重要。激光雷达作为一种遥感仪器，已经用于气象要素的探测中（风、温度、气溶胶的光学厚度等）。目前，测温激光雷达主要有拉曼激光雷达（振动和转动）、共振荧光激光雷达和Rayleigh散射激光雷达等，拉曼激光雷达需要大功率的激光器和复杂的背景滤波器；共振荧光激光雷达无法探测平流层内的温度；基于Rayleigh散射的测温激光雷达多应用于温度的相对测量，反演温度时需要建立响应函数和校准程序；基于固体腔扫描F-P干涉仪测量大气Rayleigh散射光谱来反演温度的方法，时间分辨率较低，并且该方法在测量过程中需要运动部件，所以不利于星载。在大气低层，分子的Rayleigh散射光谱会受到Brillouin散射的影响，两种散射信号叠加形成的Rayleigh-Brillouin散射光谱不再服从Gaussian分布，直接通过测量散射光谱的半高全宽来反演温度，会产生误差。基于回波能量的方法会受到气溶胶Mie散射信号的影响，所以在对流层中该方法并不适用。为了实现对流层内温度的高精度和高时间分辨率的测量，提出利用Fizeau干涉仪和PMT阵列对对流层内分子的Rayleigh-Brillouin散射光谱进行测量，并通过插值的方法来对回波信号中气溶胶Mie散射信号进行抑制，从而使Mie散射信号对温度反演的影响较小，最后将测量光谱和理论光谱进行全光谱匹配来实现温度的反演。除此之外，还对Fizeau干涉仪的自由光谱区、固体腔几何长度、腔体反射率、扫描间隔等参数进行了优化设计。为了验证本文提出方法的可行性，利用Matlab软件建立了一套仿真模型，通过模拟表明，在不考虑云、风和水汽含量的影响时，利用该方法测量对流层内的大气温度时，测量误差小于1 K。该测温方法可以对对流层内的大气温度廓线实现高精度、高时间分辨率的测量, 在测量过程中不需要使用运动部件，有较高的使用价值，并对同类高光谱激光雷达分光系统的研究具有借鉴意义, 为我国高光谱激光雷达陆基及星载应用提供了一套可行的技术方案和温度反演方法。

Research on Lidar Temperature Measurement Method Based on Fizeau Interferometer

Temperature is a key parameter of the state of the atmosphere. Temperature data play an important role in such fields as atmospheric dynamics, climatology, meteorology, and chemistry. It is also an indispensable input parameter for remote sensing inversion of other parameters. As a remote sensing instrument, lidar has been used in the detection of meteorological elements (wind, temperature, Aerosol Optical Depth, etc). And lidar techniques for the remote sensing of atmospheric temperature profiles have reached the maturity stage for routine observations. Currently, there are some types of temperature lidars, such as Raman lidar (vibration and rotation), resonant fluorescence lidar and Rayleigh scattering lidar. However, a high power laser and a complicated background filter are required for Raman lidarto ensure the accuracy of the temperature, resonance fluorescent lidar cannot detect the temperature in the stratosphere, and most of lidar based on Rayleigh scattering can only measure the relative temperature of the atmosphere. That is to say, the definition of response functions and calibration procedures is necessary for temperature retrieval. The time resolution of the method of atmospheric temperature measurement based on solid cavity scanning F-P interferometer is low. In the lower atmosphere, Rayleigh scattering spectrum of molecule is influenced by the Brillouin scattering spectrum, the superposition of two signals to form Rayleigh-Brillouin scattering spectrum, so there is a large error in temperature obtained by measuring the full width at half maximum of echo spectrum，and the particles scattering has a great influence on the retrieval results when the temperature is inverted by the integral technique. In this paper, Fizeau interferometer and PMT array are proposed to measure the molecular Rayleigh-Brillouin scattering spectrum, and the parameter optimization design of free spectral range, solid cavity length, cavity reflectivity of Fizeau interferometer and the scanning interval were carried out. And the method of reducing particle scattering effect is proposed. The information of discrete points on the RB spectral was obtained by Fizeau interferometer that the parameters was optimized, and the square method was used to get the fitting line. The temperature retrieval was achieved by comparing the theoretical spectra obtained with the 1976 U. S. standard atmospheric model and the Tenti’s S6 model. The simulation results prove that the proposed method is feasible to reduce the influence of particle scattering, and the error of atmospheric temperature between the top of the boundary layer to the top of the tropopause is less than 1K without considering the influence of cloud and wind. This temperature retrieval method can detect the absolute temperature profile with high precision and temporal resolution. There is a reference significance for the investigation of filter system of similar lidar, providing a set of feasible spectroscopic system solutions and temperature retrieval methods for our country’s ground-based and spaceborne hyperspectral thermometry lidar.