Applications of Doppler Spectral Density Data from Ka-Band Cloud Radar to Rain Drop Size Distribution Retrieval and Comparison with Optical Disdrometer Observation

Abstract:

A Ka-band cloud radar was used to observe clouds and precipitations in in Northeast of the Qinghai-Tibet Plateau. The experiment took place in Dari, Qinghai Province, China from July to September of 2019. The Doppler Spectral Density Data can be used to retrieve the cloud microphysical parameters. This work focuses on the research of cloud radar Doppler spectra processing, Ka-band radar data quality, and retrieval of Rain Drop Size Distribution and Air Vertical Motions in Tibet Plateau clouds. In this study, a stratiform and a convective precipitation case is used to retrieve the vertical air velocity in clouds and drop size distribution, and compare the DSD results with Disdrometer. The study carried out several specific works as follows: (1) The quality control (QC) should be implemented before radar data can be used, the QC methods for Ka-band radar conclude smoothing of power spectrum, denoising, and attenuation correction. (2) We utilize the liquid droplets trace methods to get the vertical air speed which can obtain Doppler spectral in static air. (3) Then the DSD was retrieved from the translated Doppler spectrum by a V-D relation. (4) Normalized Gamma Distribution is used to fit the retrieved DSD. (5) The DSD results are compared with ground Disdrometer observation. This work can provide a theoretical reference for retrieval of the microphysical parameters of cloud and precipitation with cloud radars.