Ka-band Millimeter-wave Cloud Radar Data Quality Control And Convective Process Analysis

In recent years,the millimeter-wave radar has gradually become the main way for cloud observation because of its high sensitivity,high resolution,and sustainable observation.Many scientific experiments have been conducted by the Atmospheric Profiling Synthetic Observation System hosted by the Institute of Atmospheric Physics of the Chinese Academy of Science and valuable information has been obtained.The object of this paper is Ka-band millimeter wave cloud of this system.In order to improve the data quality,the power spectrum data processing method of this radar was analyzed.At the same time,based on the data acquired by another W-band cloud radar at the observation station in the same period,the differences between the two observations were analyzed.Finally,through a snowfall convection process observed by the Ka-band cloud radar,the macro characteristics of different stages of the process were analyzed,and the water content and snowfall in the snowfall stage were inverted.The main conclusions are as follows:(1)In the processing of power spectrum data,DC leakage by hardware will cause DC interference near the zero frequency of the spectrum data.The median filtering can preserve the signal edge information while smoothing the data to facilitate cloud signal identification.For this radar,the optimal window size is 5.This article uses the "segmentation method" to calculate the noise level because of its high reliability and low time complexity.In terms of spectral parameter extraction,the signal-to-noise ratio threshold determines the quality of the data.For this radar,when the signal-to-noise ratio threshold is set to-20.99 d B,we can get the better Product information.(2)In this paper,the Ka and W-band devices are used to compare and analyze the observation capabilities from the aspects of high-level,middle-level,and low-level clouds.The results show that both radars have a good ability to detect clouds,and they have good consistency in terms of cloud contour characteristics and echo range.and the W-band cloud radar is about 5d BZ higher than Ka-band.In order to improve the accuracy of the data,the threshold method is used to obtain the height of the cloud top and cloud bottom.For cloud top height,the slope of the fitted curve of the two radars is 1.01,and the correlation coefficient is 0.71.And for cloud base height,the slope of the fitted curve is 1.06,and the correlation coefficient is0.91.(3)By a snowfall process in Yangbajing of Tibet,we find that the radar not only has a good detection ability for non-precipitation clouds and weak rain clouds,but also can perform fine detection for snowfall.With this radar,the vertical structure of the snowfall process can be obtained.In the strongest snowfall stage,the minimum echo intensity is above 0d BZ,the particle's upward velocity is distributed at 0.2?2m/s,and the downward velocity is distributed at-4?-2m/s.In the initial snowfall and weakening period,the water content of the particles is0.00?0.03g/m3,and in the peak snowfall period,the water content of the particles is 0.02?0.06g/m3.It is feasible to use the echo intensity parameters obtained by cloud radar to retrieve the snow particle snowfall amount.During this snowfall,the maximum ground snowfall amount was 0.45mm/h.the cloud radar can provide instant snowfall rate in snowfall detection,which can supplement the shortage of ground snow detectors.