## 1 Introduction
In 2000, [PERSON] [8] made a relatively complete summary of the derivation, terrain, and boundaries of electromagnetic wave propagation calculated by the parabolic equation method, and preliminarily deduced the three-dimensional parabolic equation algorithm. In 2003, [PERSON] [9] used 3D vector parabolic equations to predict path loss on flat terrain with buildings. In 2005, [PERSON] et al. [10] established a macrocell radio propagation model for mobile communication based on 3 DPE. In 2019, [PERSON] et al. [11] deduced the solution of 3 DPE, and used 3 DPE for field strength prediction for flat and irregular forest environments. In this paper, the PE model was improved to simulate the possible CCI of the over-the-horizon transmission of the communication signal on the intercity link. When electromagnetic waves encounter irregular terrain during transmission, such as wedge-shaped boundaries, more intense reflection will occur, so the modeling of complex terrain is also particularly important. In 1987, [PERSON] and [PERSON] [12] first used PE for tropospheric wave propagation problems. In 1996, [PERSON] and [PERSON] [13,14] proposed the method of continuous hybrid Fourier transform under the impedance boundary to solve PE, which greatly improved the efficiency of the SSFT algorithm. In 2000, [PERSON] and [PERSON] [15] applied the SSFT PE algorithm to irregular terrain, extended the terrain shift map algorithm proposed by [PERSON] and [PERSON] to WAPE, and deduced a new impedance boundary condition for electromagnetic wave incidents on the surface of a finite conductor, such that the WAPE solution could be adapted to the previous MFT algorithm. Numerical examples demonstrate its effectiveness on impedance surfaces with terrain slopes of 10-15 and discontinuous slope changes of 15-20\({}^{\circ}\). To accommodate terrains with larger slopes, it is recommended to combine the terrain shift map with terrain masking (knife-edge diffraction) approximations. In this paper, the WAPE-based terrain shift map algorithm and the new impedance formula are applied to the real inter-city link distribution to evaluate the atmospheric loss distribution. Since the influence of troposcatter cannot be ignored, scholars have begun to turn their focus to the influence of atmospheric ducts on troposcatter communications. In 1993, [PERSON] [16] proposed the scattering parabolic equation method based on the radio physical optics (RPO) model. This method can simply and effectively calculate the tropospheric scattering caused by atmospheric turbulence on the basis of PE. In 2009, [PERSON] et al. [17] used this method to further study the boundary layer leakage of tropospheric scattering and the propagation characteristics in evaporation ducts. In 2013, [PERSON] et al. [18] carried out experiments with three unequal-distance cross-sea circuits to study the signal fading characteristics of tropospheric scattering in the sea area where evaporation ducts occur. The evaporation duct phenomenon was found to significantly alter the fading level of the signal. In 2015, [PERSON] et al. [19] found that the atmospheric meteorological state has a great influence on the scattering loss through the study of the scattering parabolic equation. In 2016, [PERSON] et al. [20] evaluated the refractive index of the lower atmosphere and gave a propagation loss (PL) measurement; that is, using height-independent PL measurements over a range of 10-80 km to infer information about the existence and potential parameters of atmospheric ducts in the lowest 1 km of the atmosphere. Its main improvement includes turbulence-induced distance-dependent fluctuations in the forward-propagation model, where the inhomogeneous turbulence model uses parameters that are height-dependent on the mixing ducts. In this paper, [PERSON]'s RPO basic scattering model was applied to the transmission over inter-city links with evaporation ducts, and the non-uniform turbulence model proposed by [PERSON] was used for transmission calculations over inter-city links with mixed ducts.