The Study Of Dynamical And Microphysical Properties In Precipitating Clouds Based On A Continuous Wave Radar

In recent years,the ground-based vertically pointing radars have entered a period of rapid development.The signal power spectra obtained by them are important tools to study the dynamical and microphysical processes in the cloud.The C-band vertically pointing radar with frequency modulation continuous wave technology(CVPR-FMCW)is the first continuous wave radar in C hina which takes cloud and rain as detection targets.It has ultra-high spatial and temporal resolution and can obtain fine vertical structure of precipitating cloud.It has incomparable detection advantages over pulse Doppler weather radar.In C hina,ground-based vertically pointing radars rarely involve the detection of solid precipitation,and the retrieval of microphysical parameters through radar signal power spectra is often limited to liquid particles.There are few studies on the complete and continuous retrieval and analysis of dynamical and microphysical characteristics in precipitating clouds through ground-based radar.Based on the signal power spectra of CVPR-FMCW,the dynamical and microphysical characteristics of snow clouds in the middle latitudes of C hina were firstly retrieved and analyzed.Then,the dynamical and microphysical parameters of stratiform cold cloud and warm cloud precipitation during the rainy season in South C hina were retrieved,and the dynamical and microphysical characteristics of cold and warm precipitating clouds were compared.The main algorithms in this paper developed for CVPR-FMCW include:1)retrieving the fall speed of solid particles and the vertical air velocity based on the radar bimodal spectra;2)retrieving the microphysical parameters of solid and liquid particles based on radar signal power spectra;3)establishing a hydrometeor identification algorithm suitable for CVPR-FMCW;4)the decomposition of the reflectivity and liquid water content for the liquid particles;and 5)the decomposition of equivalent reflectivity(Z_e)and ice water content for the solid particles.Six snow events in the middle latitudes of C hina were studied,including four shallow events and two deep events.Generating cells(GCs)were found near the cloud top in each event.According to the vertical gradient of Z_e and radial velocity,the snow clouds can be divided into the upper convective GC region and the lower stable stratiform(St)region,and the fall streaks(FSs)associated with GCs were embedded in the St regions.In this paper,the dynamical and microphysical parameters of GC and St regions in deep and shallow snow clouds,as well as the inside and outside of GCs and FSs were retrieved and analyzed.The results show that GC locations usually correlated with strong upward air motions,while downward air motions often appeared between GCs.The upper areas of the St regions consisted primarily of weak upward motions,while weak downward motions dominated the lower areas.There was no apparent difference in vertical air motion inside and outside the FSs.The microphysical parameters were larger inside GCs and FSs compared to outside,and the differences between the inside and outside of GCs were basically the same as those for the FSs.The differences between the inside and outside of GCs were related to their dynamical characteristics,while the differences between the inside and outside of FSs were mainly caused by particles fal ing from GCs.The 29 stratiform cold cloud and 19 warm cloud precipitation events during the rainy season in South China were studied by C VPR-FMCW and the laser disdrometer.It is found that the downdrafts played a dominant role in the liquid region of stratiform cold clouds,with a small amount of weak updrafts,and the microphysical processes were mainly net evaporation.In the warm rain events,there were abundant updrafts in the clouds,which were helpful for particles coalescence,so that the cloud drops can rapidly grow into raindrops within a short time,but the updrafts also increased the probability of raindrop break up.The diameters of raindrops during warm rain were usually smaller and more discrete in distribution compared to the stratiform cold rain.The purpose of this paper is to use CVPR-FMCW to understand the vertical evolution of dynamical and microphysical characteristics in precipitating clouds.Based on radar signal power spectra,the methods of retrieving and analyzing the microphysical characteristics for liquid particles were extended to the study of solid particles.Continuous changes of dynamical and microphysical processes in precipitating clouds were obtained at low cost and the understanding of the microphysical characteristics in the solid precipitating clouds and the solid region of stratiform clouds was supplemented.Some microphysical processes inside clouds were also analyzed by the dynamical characteristics and environmental temperature and humidity.