  Monitoring continental precipitation over Europe with high resolution (2 km,
15 minutes) has been possible since the operational production of the OPERA
composites from the European weather radar networks. The OPERA data are the
essential input to a hazard assessment tool for identifying localized
rainfall-induced flash floods at European scale, and their quality determines
the performance of the tool. This paper analyses the OPERA data quality during
the warm seasons of 2015-2017 by comparing the estimated rainfall accumulations
with the SYNOP rain gauge records over Europe. To compensate the OPERA
underestimation, a simple spatially-variable bias adjustment method has been
applied. The long-term comparison between the OPERA and gauge point daily
rainfall accumulations at the gauge locations shows the benefit of the bias
adjustment. Additionally, the daily monitoring shows gradual improvement of the
OPERA data year by year. The impact of the quality of the OPERA data for
effective flash flood identification is demonstrated for the case of the flash
floods that occurred from 29 May to 3 June 2016 in central Europe.
