[A-AS10] General Meteorology

[AAS10-10] Measurement of polarization characteristics of transmitted waves in Multi Parameter - Phased Array Weather Radar

*Rintaro Okumura¹, Tomoo Ushio¹, Yuuki Wada¹, Hiroshi Hanado² (1.Osaka University, 2.National Institute of Information and Communications Technology)

Keywords:calibration, radar, dual polarization, phased array

Disasters caused by sudden atmospheric phenomena such as linear rain bands have become a social problem. However, conventional weather radars have insufficient spatiotemporal resolution and are unable to detect precursors. On the other hand, phased array weather radars (PAWR) can observe rainfall with high spatiotemporal resolution, making it possible to detect torrential rains and other events early. Furthermore, multi-parameter phased array weather radar (MP-PAWR) that simultaneously transmit and receive horizontally and vertically polarized waves have been developed, making it possible to obtain a wider range of parameters than single-polarized PAWRs. Raindrops with large diameters become flattened due to air resistance, and their horizontal cross-section becomes larger. Therefore, even if radio waves of equal strength are irradiated horizontally and vertically, the larger the raindrop, the greater the horizontal reception power.. MP-PAWR can obtain the ratio of the horizontal reception power to the vertical power (differential reflectivity: Zdr), making it possible to estimate the shape of the particles and the rainrate. Previous research has shown that when transmitting and receiving horizontally and vertically polarized waves simultaneously, the Zdr bias is minimized if the combined transmitted field is linear at either ±45°. In this study, we developed a method to measure the quality of the transmission wave in MP-PAWR. A standard gain horn antenna with high cross-polarization discrimination ratio is connected to a spectrum analyzer, and the transmission wave from MP-PAWR is received. The horn antenna is rotated in the roll angle direction and the received power is measured. For example, if a 45° linearly polarized wave is transmitted, the received power is maximized when the horn antenna is rotated 45° so that the receiving polarization plane is parallel to the transmitting polarization plane, and is minimized when it is rotated 135° so that it is perpendicular. In this presentation, we report the method of measuring the transmission wave and the actual measurement results of MP-PAWR.