Fine detection of cloud and precipitation is still a great interest topic in atmospheric research. In recent years, millimeter-wavelength cloud radars have become the major instrument for cloud and light-precipitation observation. Because of their short wavelengths, cloud radars have excellent sensitivity to small cloud droplets and ice crystals, can be configured to have high temporal and spatial resolutions, and can operate with antennas that have narrow beamwidths and limited sidelobes. In a vertically pointing mode, cloud radar can record the Doppler spectral data which can be benefited for the microphysical and dynamic study of cloud and precipitation system. As an important prerequisite, cloud radar Doppler spectra calibration is crucial for accurately calculating radar measurements, in result, this article present a calibration method for a new 35 GHz cloud radar, produced by Chinese Academy of Meteorological Sciences and plan to participate the 3td Tibetan Plateau Atmospheric Science Experiment from 2014. The accuracy of three radar noise-level compute method are assessed by using simulated data and spectra processing technologies are researched in this research. Another interesting work in this paper is the air vertical velocity retrieval by cloud radar Doppler spectra. At last, retrieval result and reliability of convective and stratiform cloud collected at Guangdong Yanjiang in June 2014 are verified and analyzed. Mainly conclusions are as follows:(1) base on gaussian characteristic of signal and white noise of cloud radar, combined with statistical fluctuation extents, the method can simulate the cloud spectra closed to real, and they can be used as an effective source data for spectra quantitative study. (2) The segment method is the most accurate and stable method, the max-speed method can be affected by noise fluctuations, the objective method is overrated as Doppler velocity and spectral width become large, as long as can cause an apparent error. (3) Inspection results by using the spectral line intensity threshold show that, all traced spectral line intensity in convective cloud are less than this threshold, 100% gates in cloud can be inverted and results are reliable. Apart from a few gates, most of traced spectral line intensity in stratiform cloud are less than this threshold too, 96% gates in cloud can be inverted reliably.
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