Recent Improvements to the Quality Control of Radar Data for the OPERA Data Centre (Odyssey)

The EUMETNET-funded OPERA Data Centre (Odyssey), which became operational in 2011, is responsible for processing centrally the radar data received from 172 European radars. The radar data volumes are typically received every 5 minutes and combined into radar composite products (Rain Rate, Maximum Reflectivity and Hourly Accumulations) that cover the whole of the Europe at a resolution of 2km, with 15 minute updates. The first version of Odyssey produced a composite product but did not include any quality control or correction procedures - the radar data was used as provided by the suppliers. However, recent work has been carried out to incorporate the BALTRAD toolbox software developed as part of the BALTRAD and BALTRAD+ projects. A tool tailored for Odyssey, called "odc_toolbox", allows the removal of spurious echoes in polar data prior to their ingestion into the composite generator. The most recent version of the "odc_toolbox" combines a hit accumulation filter (suggested by the Odyssey Team) with image processing algorithms originally designed at the Finnish Meteorological Institute to identify speckle, RLAN transmitter interference and return from ships. The hit accumulation filter simply builds up a climatology of radar echo counts (hits) and uses it to systematically reject radar pixels that exceed a chosen hit rate threshold. Much work is needed and planned as part of the OPERA4 program, which started this year, to develop the pre-processing algorithms further and to bring the quality of the Odyssey products close to quality of the national ones. Therefore there is also the need to establish a reference point, using objective verification techniques, in order to monitor future improvements. This paper gives a brief overview of the Odyssey system and presents the results of two verification studies carried out first using the UKMO gauge network and secondly using the UKMO EURO4km NWP model to identify biases in the hourly and 6-hourly accumulation fields and to evaluate the improvements brought by the first stage of QC development.