A method for determining a refractivity profile of an atmosphere of the Earth. The method may involve: generating radar signals from a radar device located above the Earth's surface toward the Earth's surface; measuring a time of flight and a reflected intensity of reflected radar signals received back at the radar device; using the measured time of flight and the reflected intensity of the reflected radar signals received by the radar device to determine a distance to a radar horizon where the radar signals are tangent to the Earth's surface; and using the distance to the radar horizon to determine a refractivity profile of the atmosphere through which the radar signals and the reflected radar signals have travelled.