基于非固定金属球的双偏振天气雷达标定方法研究

The microphysical structure of precipitation can be observed through dual-polarization weather radar. It can obviously improve the accurate of precipitation estimation using general Doppler weather radar. However, the calibration is an essential segment if monitoring and forecasting accuracy for severe weather of dual-polarization weather radar need to be improved. Hence, it is significant to develop a calibration approach which is focus on quantitative parameter of dual-polarization weather radar. Moreover, it is significant for upgrade focused on dual-polarization and improving the CINRAD weather radars in the future. Currently in China, calibration approaches of dual-polarization radar mainly include sun method, clutter calibration method, micro-raindrop method etc., these methods have some difficulties in application due to objective factors. The calibration in foreign countries is by means of metallic sphere. However the metal sphere can drift easily while the calibration process, so radar cannot trace metallic sphere to detect and scan the location accurately and automatically. By using a high accuracy location module, the radar station can receive the location information in real-time for the non-fixed metallic sphere. It means that radar can track the non-fixed metallic sphere automatically. Furthermore, through signal theory, signal spectrum estimation of Doppler radar and signal process algorithm of dual-polarization radar, it can be used for deviation analysis from the aspect of time and frequency domains by using I/Q data. Through the multi-point integration optimized identification method when the target point is calculated, it can be used for the parameter quantity calibration of dual-polarization for non-fixed metal sphere.

双偏振天气雷达能准确观测到降水的微物理结构，显著改善普通多普勒天气雷达的降水估计精度。然而，双偏振雷达想要在灾害性天气监测和预报方面具有高准确性，对雷达的准确标定必不可少。因此，研发出一套针对双偏振雷达相关各参数的定量标定方法，具有重要的研究意义，对未来新一代天气雷达偏振升级改造工作也具有实际应用价值。目前国内对偏振雷达的标定方法主要包括太阳法、地物法、微雨滴法等，这些方法由于客观因素在应用上存在困难。国外采用外部金属球标定法，然而金属球受天气因素会造成飘移，雷达有时无法准确探测到其位置。如果在金属球上附加高精度的定位模块，就可以实现雷达自动跟踪非固定金属球扫描。此后，通过多普勒雷达信号理论和谱估计、双偏振雷达信号处理算法等，利用雷达I/Q数据从时域和频域两个方面对双偏振雷达的误差进行分析。在目标点计算时采用多点融合的最优化识别方法，从而实现在金属球非固定情况下的双偏振雷达参数定量标定。

本项目的实施按研究计划进行。完成了基于非固定金属球的双偏振雷达标定试验方法设计，利用自制的高精度定位模块和伺服自动跟踪模块进行了2次标定实验；在此基础上，发展了基于信噪比识别雷达周围地物的最优算法，建立了从双偏振雷达信号谱中准确识别金属球目标的方法；在高斯自适应处理方法（GMAP）的基础上，考虑到双通道之间的一致性，在数据处理过程中幅度和相位等因素进行改进，从而优化了GMAP算法，提高了地物位置的偏振参量估算质量；开发了自动分析双偏振雷达所有偏振参量误差的软件，并将项目发展的双偏振天气雷达标定关键技术应用在气象业务部门，对上海的2部业务X波段双偏振天气雷达和南京的1部业务X波段双偏振天气雷达进行了系统标校。