Data Quality Monitoring Techniques on a Mobile X-band Doppler Polarimetric Weather Radar

MeteoSwiss operates a mobile X-band Doppler polarimetric weather radar, manufactured by Selex (model METEOR 50DX). The quality of the products of the 50DX is assured by means of different techniques designed to regularly monitor the stability and the accuracy of the radar system. An automatic daily monitoring of the polarimetric data, implemented in Python and integrated in the PyRad framework of MeteoSwiss, is performed to gather insight on the system status. The data quality check belongs thus to a framework of monitoring and calibration algorithms. Its strength lies in the combination of all the tools and the fact that it is implemented for operational usage.

 Statistics on the correlation coefficient (ρ_HV) in rain lead to information on the antenna quality, the offset of the differential phase(φ_dp) is used to monitor the influence of the transmit/received path, while the differential reflectivity (Z_DR) in rain gives indication on possible channel imbalance. The sanity of the radar system and in particular of its receiver unit is proved by measuring the sun flux both with a dedicated scan periodically performed in an automatic way every 30 minutes, as well as by analyzing the occasional sun hits occurring during the regular scans. A further aspect that is considered to monitor the radar system is the inter-comparison of the reflectivity values obtained by the X-band radar with those measured by the MeteoSwiss Rad4Alp C-band radar network within the co-located gates. The rain rate estimated by the X-band radar is compared with that measured by the rain gauges and by a disdrometer located in the vicinity of the radar. These techniques are operationally performed to validate the quantitative value of the delivered products, are not designed specifically for 50DX and can be flexibly applied to other weather radar systems..