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

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

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

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

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

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

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

Radar display after filtering

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