Verification of ADWICE in-flight icing forecasts: Performance vs PIREPS compared to FIP

This study presents an evaluation of in-flight icing severity forecasts produced for the eastern United States for the winter 09/10 using the German ADWICE icing forecasting system. An instance of the underlying COSMO-EU 7km model was run over the eastern CONUS to produce four months worth of NWP data for the ADWICE algorithm. The generated icing fields were then verified using pilot reports (PIREPS) as "truth" data. In order to be able to characterize ADWICE performance over this non-native domain against a known quantity for this part of the world, a comparative verification was performed with the American FIP icing product over 1.5 months of data, using a unified set of observation PIREPS and forecast times. Subsequently, ADWICE forecasts were verified over the whole time period and analyzed with respect to seasonal, regional or altitude variations. This publication contains a description of the ADWICE algorithm, the methodology used for verification, a discussion of advantages and disadvantages of the approach and a presentation of the relevant results. The comparison with FIP shows ADWICE to achieve a comparable skill in most aspects of icing forecasts and can therefore legitimately be evaluated on its own over a larger time period.