Hello
although I have not used it yet, I believe that in the namelist.input section of version 4.1 you will find the answer.
&radar_da
radar_non_precip_opt= 1,
radar_non_precip_rf = -999.99,
radar_non_precip_rh_w = 95.0,
radar_non_precip_rh_i = 85.0,
cloudbase_calc_opt = 1,
radar_saturated_rf = 25.0,
radar_rqv_thresh1= 40.0,
radar_rqv_thresh2= 50.0,
radar_rqv_rh1= 95.0,
radar_rqv_rh2= 85.0,
radar_rqv_h_lbound= -999.0,
radar_rqv_h_ubound= -999.0,
ciao Luca