1. Anomalous Propagation
The beam gets bent by non standard atmospheres. The results are often “surprising”

2. Anomalous Propagation (AP)
In average atmospheric conditions, little of the beam will strike the ground.
In ‘typical’ conditions (‘standard atmosphere’) .. beam will refract with a 4/3 earth model

3. Anomalous Propagation 2
If temperature profiles are far from standard atmosphere,, the beam may be bent either up or down: this path is termed anomalous propagation
This term is also used to describe the resulting echoes

4. Anomalous Propagation (AP)
Ducting of beam causing certain ground returns or targets well beyond the normal range
Doppler can filter AP

5. Anomalous Propagation (AP)
Their intensity tend to change rapidly with time, in contrast to ground clutter
Doppler processing can remove some AP
Cross check provided by satellite images or neighbouring radars

6. A/P versus Ground Clutter
Ground Clutter Echoes are constant in time (in contrast to AP, which is variable in time)
Well handled by clutter filters during signal processing

7. Radar display before filtering
Includes A/P ground clutter second trip echoes and multi-path hail spike

8. Radar display after filtering

9. Summary
Anomalous Propagation is a frequent unwanted phenomenon of weather radar.
Techniques to filter it out works reasonably well.