Abstract:The characteristics of a precipitation-fog process, which caused the occurrence of low visibility weather, were analyzed by using the imagery of millimeter-wave radar detection. The analysis of horizontal distribution characteristics of the process showed that its spatial scale was about 15 km, and the radar wave intensity ranged from -20 dBz to 25 dBz. We also analyzed the vertical structure of the process, finding that the process experienced a series of varying processes from precipitation to fog as it passed through the radar-scanned region. The analysis of radar radial velocity suggests that the main structure of the system was stable, and the edge area was compensated for the main area, so that the system could maintain and develop. The visibility began to decline when the process was approaching the visibility stations, and reached the minimum value when the process was about to leave. The visibility became better after the process left for a period of time, and no effective precipitation was observed in the millimeter- wave radar scanning area during the process.〖JP2〗 In addition, according to the empirical formula, the relationship between low-level radar reflectivity intensity and near-surface visibility in this process was well simulated, and the specific formula was Vis=2.283Z-0.121.