Abstract:A multi phase weather process with fog, haze, rain and snow seen in Beijing on 17 March 2012 is analyzed by using wind profile radar data. The results show that the profiler products are good at diagnosing and distinguishing weather change and evolution, and can reveal the detailed variation of precipitation. The profiler is usually used to detect weak horizontal wind and weak vertical movement of atmosphere in case of fog. Its air refractive index is small while signal noise ratio (SNR) below 850 hPa is strong. Simultaneously, the profiler frequency spectrum shows the features of clear weather. Before it rains, the SNR in troposphere remarkably strengthens, the profiler vertical beam radial velocity (Vr) firstly presents positive values, in the mid and high levels, which indicates the air sinking motion is enhanced. At the same time the other two double beams (Vr) are not symmetrical anymore. When it rains, all the five beams (Vr) of profiler turn positive from surface to upper air, and the largest Vr is near surface, not concentrated in the vertical beam. Correspondingly, spectrum width maintains in 1-2 m·s-1. When precipitation phase changes, spectrum width diminishes obviously while SNR strengthens, and the Vr gets weakened. These changes usually occur in the whole boundary layer to troposphere. When rain stops, the above changes show reverse features, including spectrum width increases, SNR weakens, and all the five beams return to symmetrical state.