【作者】 龙强；

【导师】 肖韶荣；

【作者基本信息】 南京信息工程大学 ， 大气物理学与大气环境， 2012， 硕士

【摘要】 本研究工作所基于的Mie散射激光雷达系统：采用染料激光器作为发射单元,波长定为560nm；光学接收单元为卡塞格林接收望远镜,配以小孔光栏限制视场,提高信噪比,光电探测器使用低噪声、高增益的光电倍增管；信号检测单元采用运算放大电路作为输出方式,并由TDS5104B示波器来实现数据的显示与存储。利用该系统实现了对南京北郊低层大气的探测,所得回波信号真实地反映了大气状况。因激光雷达实验系统采用非共轴模式,为修正近场信号,就要解决其所带来的几何重叠因子标定问题。几何重叠因子理论计算过程比较复杂,针对其曲线的趋势,假设一个简单明了且几何意义明确的指数形式,将其与理论计算结果做最小二乘法拟合确定相关参数,拟合程度理想,说明理论计算的几何重叠因子近似符合指数变化趋势；对于理论计算结果不实用以及实验法操作不便的问题,在前人近场信号修正工作的基础上,提出一种简单新标定方法：利用距离校准函数S(z)远场线性拟合以及近场二次多项式拟合获得近场修正信号,根据激光雷达方程将近场修正后的信号与原始回波信号做比,即得该系统的几何重叠因子。Klett反演算法是应用广泛比较成功的算法,此解要求一个参考高度和该高度处的消光值。提出一种基于拟合的参考消光值标定方法：利用所得的几何重叠因子对所测回波信号进行修正,采用最小二乘法对最大范围大气均匀区回波信号进行拟合,获得消光参考值。利用所提出的几何重叠因子及消光参考值的标定,对南京北郊的低层大气探测回波信号进行了大气消光反演,得到了很好的效果。更多还原

【Abstract】 In this work, firstly, the Mie scattering lidar system is built and introduced. The dye laser is the transmitter, working at the wavelength of560nm. The Cassegrain telescope is taken as the signal receiver. In order to improve the SNR, a ray bar is used to limit the field of view. The photo detector is a low-noise, high grain photomultiplier tube. The operational-amplifier circuit is taken as the output mode of the signal detection part, and a TDS5104B oscilloscope is used to displayed and stored the data. By the system, the detection of the lower atmosphere in northern suburbs of Nanjing is achieved, and the obtained echo shows the real atmospheric conditions.As the experimental lidar using non-coaxial mode, the geometrical form factor should be calibrated. The theoretical calculation of geometrical form factor is complex, so a simple exponential form, whose geometrical meaning is clear, is assumed. Make it done the least squares fitting with the theoretical calculation to determine the relevant parameters, and the result is ideal,which shows the theoretical calculation approximate to the exponential trend. To solve the problems that the theoretical calculation is not practical and experimental operation is inconvenient, a simple calibration is proposed based on the near-field correction of relevant scholars. Using the linear fitting of near-field and quadratic fitting of far-field, make the original echo signal devised with near-field signals according to the lidar equation, and the geometrical form factor is gained.Klett inversion algorithm, which requires a reference height and extinction value, is used widely and successfully. A new calibration based on fitting for reference value is presented in this paper. The echo signal is directly corrected through the geometrical form factor. The least squares method is used to fit the maximum range of atmospheric echo signals, then the reference value is gained. Using the calibration, the lower atmosphere echo signals of the northern suburb of Nanjing are inversed, and the good results are got.更多还原