【作者】 张金业；

【导师】 龚威；

【作者基本信息】 武汉大学 ， 摄影测量与遥感， 2010， 博士

【摘要】 随着我国改革开放三十年的发展,目前,建立和谐、环保的两型社会是我们的目标。因此,对我们的生存环境有了前所未有的关注。其中大气污染是最为关注的一个问题。实时、定量的大气气溶胶含量是判断大气干洁度的重要指标,也是研究气候气象变化的一个重要要素。发展及时有效的探测手段是目前全国面临的一个巨大挑战。自从激光器件问世以来,对于大气气溶胶的研究进入了一个划时代的意义,可以实时、长期观测气溶胶的垂直分布廓线,并同时出现了天基激光雷达和地基激光雷达。在利用Mie激光雷达探测反演时,一个激光雷达方程存在两个未知数,气溶胶的消光系数和后向散射系数。所以必须假设他们两者之间的关系,才能解决问题,有了假设就必然引入了误差。而利用Raman激光雷达探测,不需要作此假设,可以精确探测气溶胶的消光系数特性。本文发展了一套地基Raman/Mie多通道激光雷达系统,能够实时、准确地探测武汉地区对流层低空大气气溶胶的光学特性,从而反映气溶胶在大气中垂直分布含量情况。本文首先在总结前人工作的基础上,把握大气气溶胶研究现状和发展前景,研究激光雷达探测大气气溶胶技术,并根据武汉地区大气气溶胶现状,设计一套地基Raman/Mie多通道激光雷达系统。估算各种参数值,并仿真模拟激光雷达系统的工作特性。集成整个系统,并对系统的各个硬件以及软件部分进行调节与信号的测试。保证系统的各个通道同时、有效的工作。其次,研究大气气溶胶的消光系数、后向散射系数和激光雷达比等特性的反演方法,通过仿真实验来验证反演方法的正确性与可行性。第三,利用自行研制的Raman/Mie多通道激光雷达系统,对武汉地区大气气溶胶消光系数、后向散射系数和激光雷达比等的垂直分布廓线进行实时探测,并做长期观测,以期对武汉地区大气中气溶胶的分布以及变化规律进行研究。第四,研究目前利用激光雷达探测大气边界层的方法,并利用Raman/Mie多通道激光雷达系统探测武汉上空大气边界层的情况,分析边界层的高度、变化规律等。最后,利用此系统对逆温层进行了初步的探测研究。在研究的过程中,解决了一些关键技术问题,并对一些反演算法进行了改进。由于Raman散射信号非常微弱,所以必须对背景噪声进行有效的抑制,才能保证Raman散射信号不会被淹没。我们采用磁场探测技术,对实验室周围的电磁环境进行探测,并输入软件,对电磁噪声进行扣除；利用Raman激光雷达原理可以较为准确的探测大气气溶胶的消光系数,同时结合同一个视场的后向散射Mie信号,可以反演气溶胶的后向散射系数。这里的关键点就是要保证Mie通道信号和Raman通道信号必须来自于同一个视场。利用Raman激光雷达原理反演的激光雷达比,作为Mie散射激光雷达方程的输入条件,反演气溶胶消光系数和后向散射系数。然后比较两种方法所得的结果。如果符合程度较高,说明了两个通道的信号是来自于同一个视场；大气边界层高度是边界层研究最关心的问题之一,而不同的研究者给出了不同的边界层高度的结果,也就使得边界层高度有着不同的判据。目前已经有了很多直接观测的手段,如气象塔观测、系留气球、释放气球、遥控和驾驶飞机以及一些遥感技术。利用不同的参数作为判据,来确定边界层的高度。但最为直接有效的,还是使用激光雷达作为探测工具,可以实时、连续地观测边界层高度及其变化情况。本文提出用Raman激光雷达原理来探测反演大气边界层的高度,并对常用Mie激光雷达探测边界层的SBH99法进行改进,使具有更高的精度。同时也对出现的逆温层的高度进行了探测分析。更多还原

【Abstract】 As China’s three decades of reform and opening up, establishing society of harmony, environmental protection is our present goal. Therefore, our living environment is focused on unprecedented attention. Air pollution is one of the most concerned problems. Real-time and quantitative atmospheric aerosol content is an important indicator that determines the degree of air cleaning, but also an important element of weather in the study of climate changes. Developing timely and effective detection means is urgent.Since the invention of laser, the study of atmosphere has beening coming into a new epoch. Lidar can make real-time and long-term observations of aerosol vertical distribution profiles. There are space-based lidar and ground-based lidar, space-based lidar can detect over a wide range of areas, but is easily interfered by the weather such as cloud. So there are often blind observation areas. In Mie Lidar equation, aerosol extinction coefficient and backscattering coefficient are two unknowns. If using Mie Lidar, there must be an assumption about the relationship of them in order to solve the equation. The assumption introduces errors. However, using Raman Lidar principle, aerosol extinction coefficient can be inversed accurately without making this assumption. This paper developed a ground-based Raman/Mie multi-channel lidar system, real-time and accurate vertical distribution of aerosol optical properties in the low troposphere over Wuhan will be detected.At first, the previous work is concluded and the status quo of atmospheric aerosol research and development prospects is studied. A ground-based Raman/Mie multi-channel lidar system is designed in accordance with the status quo of atmospheric aerosol over Wuhan. All system parameters are estimated and the lidar’s operating characteristics are simulated. Then the entire including hardware and software are integrated and signal tests are done to make sure that signals in all channels are received well. Second, the methods of inversing atmospheric aerosol extinction coefficient, backscattering coefficient and lidar ratio are studied and the simulation experiments are done to verify the correctness and feasibility of the inversion method. Third, based on the self-developed Raman/Mie multi-channel lidar system, real-time vertical distribution profiles of atmospheric aerosol extinction coefficient, backscattering coefficient and the lidar ratio are detected. And long-term observations are done to get a view of atmospheric aerosols’ distribution and variation in Wuhan area. Fourth, research the atmospheric boundary layer and detect the height of it over Wuhan by the lidar system. Finally, temperature inversion in the night is surveyed based on lidar.In the course of the study, some key technical issues have been solved and some method has been improved. As the Raman scattering signal is very weak and background noise must be suppressed effectively in order to ensure the Raman scattering signal will not be submerged. We use the military detection technology to measure the surrounding electromagnetic noise and then enter it into the software for subtraction; Aerosol extinction coefficient can be retrieved accurately by the Raman lidar signals. Combined with Mie scattering signals in the same field of view, aerosol backscattering coefficient can be obtained. The key point here is to ensure that Mie-channel signal and the Raman-channel signal must come from the same field of view. Lidar ratios retrieved by Raman backscatter signals, work as the input conditions for Mie lidar equation to get aerosol extinction coefficients and backscatter coefficients. Then compare the results of two methods. If they are in good agreement with each other, the two-channels are from the same field of view. Detecting the height of atmospheric boundary layer is also a greatest concern. Different researchers can give different criterion and different results. There are a lot of direct observation techniques, such as meteorological tower observations, tethered balloon, and the release of balloons, remote control and fly jet fighters as well as some remote sensing technology. But the most direct and effective means is the lidar because it can make real-time and continuous observation. In this paper, the height of atmospheric boundary layer and its changes during the night are measured based on the Raman lidar. And the method of SBH99 in the Mie lidar analyses is improved. At the same time the detection of height of temperature inversion is also carried out.更多还原