Quality of Radar echo top heights

The echotop height, i.e. the maximum height where a given reflectivity is observed, provides valuable information in case of thunderstorm situations. It allows to evaluate the vertical extension of thunderstorm cells, which is an indicator of the storm severity and the probality that hail is produced. Echotop values are not only affected by errors on the measured reflectivity itself but also by errors on the height assigned to these reflectivities. In this study we evaluate the relative importance of these errors as a function of range.

The method is based on the comparison between reflectivity data observed at different elevation angles by two radars located in Belgium and The Netherlands and distant from 244 km. For each radar, the reflectivity field on a vertical cross section extending between the two radars can be extracted from the volume data. Twenty-five thunderstorm episodes observed in the summers of 2002, 2003 and 2004 have been considered and a total of 872 vertical cross section pairs have been extracted and compared. These comparisons allow to identify the dominant sources of errors and to quantify the degradation of the quality of echotop height with range.