论文部分内容阅读
在用激光雷达方程反演大气消光系数时,大气消光系数边界值对反演精度影响较大,而在低层大气中该值较难确定。文中提出了一种基于改进牛顿法的大气消光系数边界值确定方法,其核心思想是,把确定大气消光系数边界值的问题转化为求非线性方程的数值解。首先,根据大气消光系数边界值与激光雷达回波信号功率以及大气光学厚度之间的关系,假设大气消光系数边界值为x,构建一个非线性方程。其次,采用改进的牛顿法求非线性方程的数值解,得到大气消光系数边界值。使用香港天文台装置在香港国际机场的多普勒激光雷达回波信号数据,对该方法的可行性和可靠性进行了验证。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。该方法收敛速度快,迭代次数少,并且不需要计算导数值,极大地减少了运算量,具有较强的实际应用价值。
The atmospheric extinction coefficient boundary value has a great influence on the inversion accuracy when using the Lidar equation to retrieve the atmospheric extinction coefficient, which is difficult to determine in the lower atmosphere. A method to determine the boundary value of atmospheric extinction coefficient based on the improved Newton method is proposed in this paper. The core idea is to convert the problem of determining the boundary value of atmospheric extinction coefficient into the numerical solution of the nonlinear equation. First of all, according to the relationship between atmospheric extinction coefficient boundary and lidar echo signal power and atmospheric optical thickness, assuming that the atmospheric extinction coefficient boundary value is x, a nonlinear equation is constructed. Secondly, using the improved Newton method to find the numerical solution of the nonlinear equation, the atmospheric extinction coefficient boundary value is obtained. The Doppler lidar echo signal of the Hong Kong International Airport installed by the Hong Kong Observatory was used to verify the feasibility and reliability of this method. The results show that using this method to determine the boundary value can accurately reflect the lower atmospheric extinction coefficient. The method has the advantages of fast convergence, less iterations and no need to calculate derivative values, which greatly reduces the computational complexity and has strong practical value.