一种C波段雷达反射率因子衰减订正方法——径向拟合法

A method for attenuation correction of reflectivity factor of C-band radar:radial fitting method

针对南京信息工程大学C波段双线偏振多普勒天气雷达回波强度的衰减订正提出一种新方法——径向拟合法,将衰减更小的南京站S波段天气雷达观测数据插值为与C波段雷达相同的空间分辨率,依次径向拟合两雷达回波强度差,保证衰减量随距离的增加而逐渐变大,将拟合结果用于径向拟合衰减订正算法。先用小波分析法和变距离最小二乘法对雷达数据进行预处理,再对比分析ZH-KDP法和径向拟合法订正前后回波强度-距离廓线图及偏振参量KDP-ZH散点图。结果表明:2种方法订正后的回波强度均有所增加,ZH-KDP法受雨滴谱、雷达标定等因素的影响,在近距离处订正量偏小,远距离处订正量偏大;径向拟合法订正后的回波强度与S波段实测数据一致性较高,不受经验系数、降雨类型的影响,计算简单,能够显著提高雷达回波强度的数据质量。

This paper proposes a new method, named radial fitting method, for the reflectivity factor attenuation correction of C-band dual-polarization Doppler weather radar (abbreviation: C-pol) of Nanjing University of Information Science and Technology. The S-band radar observation data is interpolated to the same spatial resolution with the C-pol, and radial fitting the difference between the two radar echoes in turn to ensure that the attenuation gradually increases with the increase of the distance. Results of radial fitting are used for attenuation correction. Preprocessing of radar data by wavelet analysis and variable distance least squares is done;the profile of reflectivity factor with distance before and after correction is compared, and the distribution of scattered plots of K DP - Z H is also analyzed. Results show that the corrected reflectivity factors of the two methods are all increased. The Z H- K DP method is affected by radar calibration. The correction amount at the long distance is large, and the correction amount at the short distance is small. The results of the radial fitting method are not affected by the empirical coefficient and rainfall type. It has a good agreement with the S-band reflectivity factor and can significantly improve the quality of radar data.