Anomalious propagation (AP) is a mirage on a radar. Ground clutter, high superrefraction, echos beyond maximum unumbiguous range and biometeors, mountains are common AP signatures. If there are data from more than one radar, AP and false echos are easy to identify, because the neighboring radars generally won't see the same thing. If only one radar is available, it is possible to look at different elevation angles and it can be found that AP tends to be confined to the lowest elevation angles.
