中文摘要：

本文以激光雷达测量机场跑道斜程能见度为应用背景，提出了一种基于不动点原理的大气消光系数边界值确定方法，将确定消光系数边界值的问题转化为求解函数不动点。首先在边界层底部选取参考点，假设一个消光系数边界值，在Klett反演算法的基础上，构建消光系数均值与边界值之间的函数关系。然后依据函数不动点存在性和唯一性的条件判断不动点的存在，通过迭代使消光系数均值收敛到不动点，并同时获得消光系数均值和消光系数边界值。通过仿真实验验证该方法在非均匀大气条件下的有效性后，将其用于实际激光雷达回波信号的反演，得到低层大气消光系数垂直廓线，并与用洁净层法确定边界值所得的结果进行了对比。结果表明，利用该方法确定边界值，可以较为准确地反演出低层大气消光系数。

英文摘要：

In this paper,in order to measure the slam visibility at the airport runway using a lidar,a method based on the fixed-point principle is proposed to determine the boundary value of the atmospheric extinction coefficient. Using the method, the problem is reduced to the problem of searching for the fixed point of a function. A reference point in the bottom boundary layer was firstly selected and a boundary value of the extinction coefficient was assumed. The function between the mean extinction coefficient and its boundary value was constructed based on the Klett inversion algorithm. Secondly, the existence of the fixed point was judged according to the existence and uniqueness condition, and the extinction coefficient converged to the fixed point through iteration. Consequently, the mean extinction coefficient and its boundary value were obtained. After the availability of the method under non-uniform atmospheric conditions had been verified by numerical simulations, the method was applied to invert the extinction coefficient from the real lidar return signals. The vertical profiles of the atmospheric extinction coefficient were further obtained. The results show that under the lower atmospheric condition,the proposed method for determining the boundary value can be used to invert the atmospheric extinction coefficient more efficiently than the clean-layer method.