Evaluation by Radar-Radar Comparison of the Attenuation Correction Used Within the Operational Radar Data Quality Control Scheme at Deutscher Wetterdienst (DWD)

The correction of precipitation-induced attenuation plays an important role in ensuring the quality of the operational dual-polarisation C-band radar data of the German Weather Service (DWD). As with most polarimetric moments, direct validation of the algorithms used is difficult as no known truth exists.

To examine and compare the quality of the attenuation correction algorithms, we use an inter-radar comparison. The attenuation-corrected and pre-corrected data from one radar are evaluated in the beam volume above the location of a neighboring radar and compared with the vertical so-called "birdbath" scan there. Due to the fine 25 meter resolution of the birdbath scan and the short-range measurement, statistical uncertainties in the measurement can be estimated and attenuation errors can be minimized. With statistics over longer periods of time and numerous radar-radar pairings, we can assess the quality, strengths and weaknesses of the underlying attenuation correction algorithms.

We present the details of the inter-radar comparison method and show results for attenuation corrections using different specific differential phase (KDP) calculation methods as a data basis.