Diffraction over simple terrain obstacles by the method of parabolic equations

The authors document initial work on a method of adapting the split-step method of solving the parabolic equation for use on irregular terrain. The proposed extension models the terrain by linear segments of arbitrary gradient, however for the parabolic approximation to remain valid the gradient must not be larger than about 15°, but step discontinuities are allowed. The initial investigation looks at the fundamental building block of this model, the flat-topped block. This proposed extension to the existing model may provide a useful way forward in making the parabolic equation method (PEM) applicable to a more general range of tropospheric propagation problems that include not only anomalous propagation conditions but irregular terrain profiles