大气水汽探测激光雷达系统仿真与数据反演

发布时间：2018-03-17 01:27

本文选题：大气水汽　切入点：星载　出处：《北京理工大学》2014年博士论文　论文类型：学位论文

【摘要】：水汽作为大气的一个重要组分，在降水、能量输送、辐射平衡、云的形成、天气和气候灾害性监视和预报中起着重要作用。激光雷达作为一种主动大气遥感手段，具有实时连续监测、空间分辨率高、探测精度高等优点。根据工作平台不同，探测大气水汽的激光雷达主要有地基拉曼散射激光雷达和星载距离分辨差分吸收激光雷达。本文对大气水汽探测地基拉曼散射激光雷达和星载距离分辨差分吸收激光雷达系统设计和反演算法展开了研究。论文主要研究内容包含三部分，首先完成了白天和夜晚有效测量中低部对流层水汽分布的地基拉曼激光雷达仿真设计；其次完成了测量地表至平流层层底水汽分布的星载距离分辨差分吸收激光雷达系统仿真设计；最后针对以上两种激光雷达仿真回波信号研究了相关数据处理方法。本文完成的主要创新性工作如下： 1)完成了能够实现中低部对流层水汽昼夜观测的拉曼散射激光雷达系统仿真设计。根据中低部对流层大气模式、水汽拉曼散射激光雷达回波模型和噪声模型，分析了激光器发射波长、能量、望远镜口径、大气能见度等因素对系统回波信噪比，评价了发射系统、接收系统和大气环境对大气水汽探测地基拉曼散射激光雷达探测性能的影响。最终确定采用532nm作为发射波长采用闪耀光栅分光的地基拉曼激光雷达系统设计方案，仿真结果表明：白天探测高度为4km，夜晚探测高度为9km，能够满足中低部对流层水汽廓线探测要求。 2)完成了测量地表至平流层层底水汽分布的星载距离分辨差分吸收激光雷达系统仿真设计。根据中纬度大气标准模型给出的大气气溶胶、分子、水汽分布模型，利用引入多普勒展宽修正后的星载距离分辨差分吸收激光雷达回波模型和噪声模型，分析了激光器能量与频率稳定性、望远镜口径与视场角、大气环境、激光束指向等因素对系统回波信噪比和测量性能的影响。最后完成了大气水汽探测星载距离分辨差分吸收激光雷达系统各主要部分的设计参数，仿真结果表明：该系统能够实现海拔高度15km以下的水汽分布测量。 3)针对大气水汽探测地基拉曼散射激光雷达和星载距离分辨差分吸收激光雷达的微弱回波信号提出了一种新阈值去噪法。该方法克服了原有硬阈值函数不连续、软阈值函数丢失高频信息的缺陷。分别采用计算机仿真模拟信号和激光雷达实际信号进行去噪验证。在对计算机仿真信号去噪时，定量分析MSE和输出信噪比可知改进后的新方法在信号去噪和有用信息保留优于原有硬、软阈值函数法；在对实际回波信号去噪时，近场信号去噪效果良好，根据回波信号的远近同时对信号采用新阈值函数法去噪和软阈值函数法去噪处理能够更有效地提取有用信息、滤除噪声。 4)利用上述新阈值函数去噪法对大气水汽探测地基拉曼散射激光雷达和星载距离分辨差分吸收激光雷达仿真回波信号进行反演，对比1976美国标准大气模式后，给出了系统探测相对误差。结果表明：大气水汽地基拉曼散射激光雷达仿真系统回波反演后海拔5km以下的相对误差小于20%，星载距离分辨差分吸收激光雷达仿真系统回波反演后海拔15km以下的相对误差小于20%；验证了探测水汽的地基拉曼散射和星载距离分辨差分吸收激光雷达系统设计的合理性。另外需要指出的是针对星载距离分辨差分吸收激光雷达仿真回波信号的反演是按照引入多普勒展宽修正的新反演算法进行的。
[Abstract]:Water vapor as an important group in the atmosphere, precipitation, energy transport, radiation balance, cloud formation, plays an important role in weather and climate disaster monitoring and forecasting. The laser radar as an active atmospheric remote sensing, with continuous real-time monitoring, high spatial resolution and detection precision. According to the working platform different lidar atmospheric water vapor are the main foundation of Raman scattering and laser radar range resolution spaceborne differential absorption lidar.
The foundation of the atmospheric water vapor detection Raman scattering laser radar and spaceborne range resolution differential absorption lidar system design and inversion algorithm are studied. The main contents of this thesis include three parts, first finished the day and night measurement of Raman lidar ground simulation design of the lower part of the troposphere water vapor distribution; secondly the bottom layers of water vapor the distribution of range resolution spaceborne differential absorption lidar system simulation design to measure surface advection; finally, in view of the above two kinds of laser radar echo signal simulation of data processing methods.
The main innovative work done in this article is as follows:
1) completed to achieve the Raman scattering laser radar system simulation design of the low tropospheric water vapor diurnal observation. According to the mode of the lower part of the troposphere, the water vapor Raman scattering laser radar echo model and noise model, analysis of the laser emission wavelength, energy, telescope aperture, atmospheric visibility and other factors on the system SNR, evaluation transmission system, receiver system and atmospheric environmental impact of atmospheric water vapor detecting foundation Raman scattering lidar. Ultimately determine the design using 532nm as the foundation of Raman lidar system using blazed grating light emission wavelength, the simulation results show that the daytime observation height is 4km, the night detection height is 9km, which can meet the low troposphere water vapor profile detection requirements.
2) the bottom layer of the vapor distribution range resolution spaceborne differential absorption lidar system simulation design to measure surface advection. According to atmospheric aerosol, given the midlatitude atmosphere of the standard model molecules, water vapor distribution model, using Doppler broadening corrected distance resolution spaceborne differential absorption laser radar echo and noise model model of laser energy and frequency stability are analyzed, and the angle of view of the telescope, the atmospheric environment, the effect of laser beam direction and other factors on the system SNR and measuring performance. The final completion of the atmospheric water vapor detection satelliteborne range resolution parameters of differential absorption lidar system for the main part, the simulation results show that: the system can achieve below the altitude of 15km water vapor distribution measurement.
3) for detecting ground atmospheric water vapor Raman scattering laser radar and spaceborne range resolution differential absorption lidar echo signal points proposed a new threshold denoising method. This method overcomes the hard threshold function is not continuous, defect of soft threshold function loss of high frequency information respectively. By computer simulation and laser radar the actual signal signal denoising. In computer simulation to verify the signal denoising, new method for quantitative analysis of MSE and the output signal-to-noise ratio shows that the improved denoising and useful information in the signal remains better than the original hard and soft threshold function method; in the actual echo signal denoising, near-field signal denoising effect is good at the same time, according to the echo signal of distance signal using the new threshold function denoising method can effectively extract the useful information, and the soft threshold function denoising method of filtering noise.
4) using the new threshold function for detecting ground atmospheric water vapor Raman scattering laser radar and spaceborne range resolution differential absorption lidar echo signal denoising simulation inversion method, comparing the 1976 US standard atmospheric model, the relative error detection system are given. The results show that the atmospheric water vapor foundation Raman scattering laser radar simulation system echo inversion the relative error below 5km above sea level is less than 20%, the range resolution of spaceborne differential absorption laser radar echo simulation system after inversion relative error below 15km above sea level is less than 20%; the detection of water vapor to verify Kiraman scattering and distance resolution spaceborne differential absorption laser radar system design rationality. In addition it is for satellite the range resolution of differential absorption laser radar echo signal simulation inversion is carried out in accordance with the introduction of the new inversion algorithm of Doppler broadening of the modified.

【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN958.98

【参考文献】