A Case Study of Deriving Vertical Air Velocity from 3-mm Cloud Radar

The vertically pointing cloud radar (WACR) can measure not only the reflectivity of cloud particles but also Doppler spectra. Retrieval of vertical air motions in cloud is demonstrated using measurements by WACR at Shouxian site during a period of 1 November 2008. The distribution characteristics of reflectivity, Doppler mean velocity, and spectral width are initially discussed. Retrieval of vertical air motions is demonstrated by the liquid droplets trace method and the improved w0－Z relationship method which is based on the liquid droplets trace method. The results are comparatively analysed with Doppler spectra. The liquid droplets trace method performs great effect in the retrieval of vertical air motions in the weak turbulence. When the turbulence is strong, the error cannot be ignored. The improved method presents good performance in the area with strong turbulence.