In electromagnetism, attenuation over an imperfectly conducting spherical earth in excess of that over a perfectly conducting plane.

The term attenuation refers to the reduction with distance from the source of the intensity of an electromagnetic signal propagating through the atmosphere caused by the interaction of the signal with gaseous constituents of the atmosphere, aerosols, or hydrometeors.

It also includes the reduction of intensity of a radiation as it passes through a medium and it includes reductions due to both absorption and scattering.