Interference region
From Glossary of Meteorology
interference region
That region in space in which interference between wave trains occurs.
In microwave propagation, it refers to the region bounded by the ray path and the surface of the earth that is above the radio horizon. Interference lobes and height-gain patterns are formed in this region by the addition of the direct and the surface-reflected wave. By contrast, the diffraction zone lies below the radio horizon.
