FILCOH—A Novel Technique to Reduce Ground Clutter Echoes in Precipitation Radars Operating in Multiple PRT

FILtering by COHerence (FILCOH) is a novel technique for mitigating ground clutter echoes of weather radar, particularly those transmitting in multiple pulse repetition time (PRT) schemes. FILCOH takes advantage of the differences in correlation time for separating rain and ground echoes. In short, the longest time-lag coefficients of the autocorrelation function are used to estimate the ground clutter contribution which is then subtracted from the shortest lag coefficients before the extraction of the meteorological parameters using the conventional estimators. The initial results are obtained for uniform PRT data provided by the Degreane Horizon wind profiler radar. The analysis illustrates the behavior of FILCOH filtering and its high performance in such cases. The simulation results are then presented for 2- and 3-PRT pulse schemes using standard PRT ratios. For the 2-PRT scheme, FILCOH filters out the ground clutter echoes up to a clutter to signal ratio (CSR) of 65 dB for the received power and up to 45 and 60 dB for the radial velocity and spectrum width, respectively. For the 3-PRT scheme, ground clutter filtering is effective up to $CSR = 45$ dB for the received power and up to $CSR = 35$ dB for radial velocity and spectrum width. These results are confirmed by 3-PRT real data issued from the French X- and C-band radars. The observed performances are, however, a little less than those of the simulation since we observed a maximum 40-dB attenuation of the ground clutter echoes of the studied rain events.