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

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.