Identification of Vertical Profiles of Reflectivity from Volume Scan Radar Data

The vertical variability of reflectivity in the radar beam is an important source of error that interferes with a reliable estimation of the rainfall rate by radar. This source of error can be corrected if the vertical profile of reflectivity (VPR) has been previously determined. This paper presents a method for determining local VPRs from volume scan radar data, that is, from radar data recorded at multiple elevation angles. It is shown that the VPR directly provided by volume scan radar data differs from the true one, which can make it inappropriate to the correction of radar data for the VPR influence. The VPR identification method, based on the analysis of ratios of radar measurements at multiple elevations angles, is then described. The application conditions of the method are defined through sensitivity tests applied to a synthetic case. A “real world” case study allows performing a first evaluation of the proposed method. This analysis demonstrates that the identification of local VPRs and the correction for their influence at a scale of about 100 km2 contributes to improving the reliability of rainfall measurement by radar. Moreover, it is shown that a correction of radar data based on identified VPRs performs better than a correction based on the VPRs directly deduced from volume scan radar data. This last point confirms the importance of the VPR identification stage in the correction of radar data for this source of error.