ARC-Based Absolute Calibration Method for Weather Radar Reflectivity

The detection accuracy of weather radar directly affects the precision of meteorological monitoring and early warning, so it is important to establish a mature calibration framework. Active radar calibrator (ARC) can generate simulated targets with predefined Doppler frequency and radar cross section (RCS) at designated distances and serve as a critical tool for end-to-end absolute calibration of weather radars. This study proposes an ARC-based absolute calibration method for weather radar reflectivity (Z) and develops a weather radar active calibrator (WARC) tailored for meteorological applications. First, a calibration model for Z was established based on electromagnetic scattering theory, considering factors such as WARC-radar distance, atmospheric attenuation path differences, and radome losses. Second, a traceable WARC-RCS calibration chain was constructed to align measurements with national metrological standards. Finally, cross-validation experiments on the accuracy of WARC and passive suspended metal spheres were conducted at Changsha Meteorological Radar Calibration Center, by using an S-band reference weather radar. Results demonstrate that the WARC system simultaneously generates four simulated targets with quantifiable parameters. The mean calibration error for Z was −0.325 dB, while velocity and spectral width mean errors were −0.041 and 0.021 m/s, respectively. The WARC performance aligns closely with that of traditional metal sphere calibration (MSC) methods, confirming both the accuracy and practicality of the simulated targets it generates.