垂直天线阵观测信息反演大气折射率廓线

Remote sensing of atmospheric refractivity from field measurements of vertical receiver array

利用垂直天线阵观测得到的电磁场信息建立目标泛函,从电磁波抛物方程传播模式出发,利用偏微分方程最优控制中的伴随方法研究大气折射率廓线反演问题.针对反演的不适定性,采用正则化思想对目标泛函进行改造,并根据变分同化思想构建反演迭代格式.数值模拟试验验证了理论算法的可行性.由于采用分步Fourier算法求解电磁波抛物方程传播模式和伴随模式过程中产生的固有误差随着传播距离的增加累积增大,反演廓线在传播距离较远时不能收敛于观测廓线.在这种情况下,引入较好的初猜廓线和背景场可以有效地改进反演结果.

In this paper we put forward a possibility of refractive index profile retrieval using field measurements at an array of radio receivers through the variational adjoint approach.The derivation of the adjoint model begins with the electromagnetic parabolic equation for a smooth,perfectly conducting surface and horizontal polarization conditions.To deal with the ill-posed difficulties of the inversion,the regularization idea is introduced into the establishment of the cost function.Based on the variational assimilation idea,the retrieval iterative format is constructed.Numerical experiments demonstrate the feasibility of theoretic algorithm for refractivity estimation.However,using the split-step Fourier algorithm to solve the forward model and the adjoint model,the intrinsic error of the solutions will increase with the extension of the propagation range,which reduces the inversion accuracy at long distance propagation.Through adopting a good initial refractivity profile and introducing the background fields in the cost function the inversions could generally be improved.