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Study of the Lidar Techniques for Remote Sensing of the Atmospheric Temperature and Aerosol Profiles

Author: LiuJun
Tutor: HuaDengZuo;LiYan
School: Xi'an University of Technology
Course: Mechanical Engineering
Keywords: Rotational Raman lidar Temperature Aerosol High-spectral-resolution lidar Boundary layer
CLC: TN958.98
Type: PhD thesis
Year: 2008
Downloads: 961
Quote: 4
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Abstract


Atmospheric boundary layer, which is closest to the surface of the earth, influences the activity of human being. The human activities in day-to-day directly affect the state of the atmospheric boundary layer. Therefore the study of atmospheric boundary layer is though of very importance for the solar radiation and heat transfer geodynamics, explanation of global warming phenomenon, improvement of local weather forecast accuracy, prevention and treatment of air pollution, especially for urban meteorological change. Atmospheric lidar, as an active remote sensing tool, has been proved to be powerful in atmospheric measurement, with a large detection range, high spatial resolution, continuous monitoring with high accuracy and real-time. It has been widely used in the research fields of laser atmospheric transmission, global climate prediction, radiation effect of the atmospheric aerosol and environment monitoring.This thesis mainly focuses on the fine detection of atmospheric temperature profiles in the boundary layer and the aerosol profiles in the troposphere. Methods and key techniques of rotational Raman scattering lidar with high-accuracy detection of lower atmospheric temperature during daytime are studied. Characteristics of Xi’an urban aerosol spatial variations are also observed and analyzed with Mie scattering lidar. A kind of high-spectral-resolution lidar for accurate profiling of atmospheric aerosol optical properties is proposed.In order to eliminate the strong solar background during daytime and high-density aerosol influence on the temperature detection in the lower atmosphere, a new spectroscopic filter is proposed for the UV temperature lidar system based on rotational Raman scattering. With the help of combination of high-spectral-resolution grating and an edge-mirror, the major portion backgrounds yielded from the solar and Mie and Rayleigh scattering are blocked. To achieve a high noise suppression rate, narrow-band interference filter is used to reject the remaining Mie-Rayleigh scattering signal in each Raman scattering channel. Theoretical analysis and experimental results show that the lidar system and the detection methods can suppress system noise effectively. And the accurate profiling of the lower atmospheric temperature during daytime can be achieved. The temperature error less than 1K is obtained up to 2.3 km for nighttime and 1.8 km for daytime measurement with 250 mJ laser pulse energy and 4 minutes observation time.For the needs of urban aerosol profiling in Xi’an and sand storms forecasting, the research of the aerosol observation experiment by Mie lidar and corresponding data procession of aerosol optical properties has been developed. The aerosol distribution data in Xi’an was given firstly. For real-time observing three-dimensional profiles of aerosol, a small portable scanning lidar system was designed to detect the optical properties of atmospheric aerosols and cirrus, horizontal visibility and so on.For fine detection of atmospheric aerosol profiles, an UV high-spectral-resolution lidar system was proposed and established on the basis of analyzing the existing technique of aerosol detection and data inversion. The system uses a high-spectral resolution grating to split solar background spatially to meet the requirement of daytime detection. Since the system uses a Fabry-Perot etalon to split out the Doppler broadened Rayleigh scattering signal, the concentration of aerosols have no influence for the detection results. By use of the diffraction effect of the grating, the system may detect the water vapor profiles simultaneously.

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