Objective Identification of Echoes Due to Anomalous Propagation in Weather Radar Data

Serious contamination of weather radar data can occur in atmospheric conditions that cause anomalous propagation of the radar beam. Excessive downward refraction of the beam may be sufficient to cause ground returns (“anaprop”), which may be difficult to distinguish from rainfall echoes. At the U.K. Meteorological Office, an automatic scheme has been devised to combine several sources of evidence, by means of Bayesian statistics, to estimate the probability that an echo is caused by anaprop. Currently, the scheme uses hourly surface observations, Meteosat infrared images, a climatology of anaprop echoes, and detected lightning, but additional independent sources would be easy to add. Results from the automatic scheme have been compared with those from an interactive quality control procedure and show agreement of around 90% in the cases evaluated. Promising areas for extension and refinement of the scheme are suggested.