A full link active calibration method and field experiment for dual polarization weather radar

Abstract

A large number of weather operational radars were deployed around China in the past twenty years, those radar aregradually being upgraded to dual-polarization weather radars. Polarized variables play an important role in improving radar data quality, quantitative precipitation estimate and hydrometeor classification algorithm. Calibration is the key basis for successful application of dual polarization radar. At present, the main calibration methods for dual polarization weather radar consist of signal source method, solar method, light rain method, metal ball method, etc. In this paper, a full link active calibration method is applied to calibrate the dual-polarization weather radar. The full link active calibration device first receives the horizontal polarization wave and vertical polarization wave transmitted by the radar, and retrieve the time-frequency characteristics of the transmitted waveform, such as pulse waveform, transmitted central frequency and other information. Based on the acquired transmission information, the device quickly generates the simulated target with specific distance, polarized characteristics and Doppler information. Secondly, through the Up conversion, and Amplifier modules, the calibration signal is transmitted back to the radar, then the radar completes the calibration signal reception and polarized variables extraction. Compared with the variables pre-defined by the calibration device, the systematic bias for radar polarized variable are determined. From September 16 to 20, 2019, the full link active calibration experiment was designed and carried out in the main campus of Chengdu University of information technology. The X-band dual polarization weather radar is located on the top of the school's information building. The calibration device adopted the high-precision radar target simulatorfrom Palindrome and is placed on a roof with a distance of 1.574km to the radar. The calibration project includes reflectivity, differential reflectivity and Doppler velocity. The results show that the reflectivity bias is 0.96dB, the differential reflectance bias is 0.8 dB, the Doppler velocity bias is 0.1 meter per second, and the azimuth positioning bias is 0.09 degree. The experimental results show that the full link active calibration method plays a positive role in promoting the development of dual-polarization weather radar calibration.