S波段双线偏振雷达差分相移率自适应计算研究

Adaptive calculation of specific differential phase for S-band dual-polarimetric doppler radar

业务用S波段双线偏振雷达受地物干扰和非均匀充塞(简称NBF,下同)影响会造成定量估测降水等方面的应用误差。该文设计了一种自适应计算差分相移率的方法,即对差分相位数据退相位折叠处理后,针对是否非NBF径向,分别利用信噪比和相关系数进行气象和非气象回波的识别并订正NBF径向相关系数。再对径向差分相位进行9阶和25阶平滑滤波。最终通过反射率和订正后的相关系数选择9点或25点最小二乘法(LS)计算差分相移率。其结果表明:差分相位折叠是影响差分相位数据质量及后续差分相移率计算的因素之一;本文提出的方法能够有效区分NBF径向中的气象和非气象回波;NBF径向相关系数的订正方法能够改善NBF径向相关系数低估的问题;9阶和25阶滤波窗的选用在差分相位曲线适度平滑的基础上,保留正确的变化趋势;同时9点和25点LS的自适应选取,保证了差分相移率的最终计算结果更符合实际的相位变化情况。

The polarization moments of S-band dual-polarimetric radar are mainly affected by ground clutter jamming and non-uniform filling(hereinafter called NBF), which cause the application errors for quantitative precipitation estimation. In this paper, an adaptive calculation algorithm is proposed to calculate the specific differential phase. The specific calculation steps are as follows. After the differential phase is unfolded, a preliminary recognition of the meteorological and non-meteorological echo is made using the signal-to-noise ratio or correlation coefficient to distinguish whether NBF is radial or not. The correction of correlation coefficient is then adopted for the NBF radial. Then the Order(9) or Order(25) filtering window is used to smooth the differential phase and interpolate the non-meteorological block. Based on the reflectivity and the corrected correlation coefficient, the specific differential phase is finally calculated by the 9-point or 25-point least square method(LS). The results show that the differential phase fold affects the quality of differential phase data as well as the following calculation.The proposed method can distinguish meteorological and non-meteorological echoes effectively. The correction of NBF radial correlation coefficient can improve the underestimation of correlation coefficient. The combination of Order(9) and Order(25) filter windows can preserve the original trend as well as smoothing the differential phase curve. And the application of 9 points and 25 points LS method promotes the calculated differential phase closely toward real values.