I recall back in the day listening to Radio Luxembourg on 208 metres in Scotland. There was a strange phenomenon when their sky wave interfered with their ground wave at dusk or near dusk in wintertime.
Also, while operating my hobby pirate station all those years ago from a TX site that was near the top of a hill, down in the valley nearby, almost in line of sight from my half-wave 40 metre dipole, my sky wave began to interfere with my ground wave at dusk. It sounded similar to the so-called LUXY EFFECT; there were nulls, and the peaks were attenuated - destructive and constructive interference ocurring simultaneously as the ground wave never faded at all so close to my HF aerial. The resultant deep fading caused by my sky wave was noticeable because it hampered reception.
Throwing 2 stones close to each other into a pond can demonstrate this kind of effect in terms of the resultant ripple and its amplitude. The peak of the constructive interference part of the wave cycle will be the sum total of the amplitudes of the waves produced by the two stones in their own rights. However, the destructive part of the cycle wiill produce a deep trough. So, attenuation will occur.