Microphysical Characteristics And Vertical Structure Of Precipitation From Radar Observations

To better describe the microphysical processes inside precipitation cloud and obtain more meticulous vertical Structure of it,a new research is started by using the L band wind profiling radar(L-WPR) and the new C band frequency modulation continues wave radar(C-FMCW).This research is mainly focused on the following four aspects:(1)radar system calibration;(2)etrieving radar raindrop size distribution based on echo power spectrum and calculating microphysical parameters;(3)identifying the bright band, analyzing melting processes and classifying the precipitation clouds;(4)analyzing the vertical characters of precipitation clouds in different regions.The radar data used in this research is from the observation experiments organized by State Key Laboratory of Severe Weather between 2011 and 2014.Calibration of L-WPR system is implemented on signal source, signal processor and signal receiver respectively by using calibration curve in signal processing.As for C-FMCW radar, a two-dimension FFT signal processing technique is applied and the lowest echo power is 170dbm.Radar raindrop size distribution can be retrieved based on echo power spectrum from C-FMCW radar. Specifically,extract vertical air motion from the observed doppler velocity spectrum and correct the falling velocity of raindrops,then use the final falling velocity to retrieve the rain drops size distributions(DSDs).Microphysical parameters of rain can be calculated by using a gamma function to fit the DSDs which have been retrieved.Analysis of the bright band can help us understand the microphysical characters of the melting layer.Radar echo spectrum density can distinguish the distribution of solid particles and liquid particles and help us watch the process of solid particles melting. In the upper melt layer,the melting process is mainly adsorption growth while in the lower melt layer,it is mainly breaking up.Vertical characters of precipitation are varied with regions and seasons.In the upstream of vapor conveyor from the Bay of Bengal, precipitation clouds are mainly stratiform while in the Tibetan Plateau, the vertical structure is deeply convective,and during plum rain season mixed clouds precipitations are more observed.