Characteristics Of Rain Drop Size Distribution And Its Application For Weather Radar Measurement In Nanjing

Rain drop size distribution(DSD)contains plenty of information,reflecting not only microphysical characteristics of the rainfall,but also macro-physical properties like rainfall type,rainfall intensity and so on,and has important applications in radar meteorology.Based on the data collected by a Parsivel laser spectrometer at Nanjing University of Information Science and Technology,Nanjing,from 2015 to 2016,the dataset of 32 rainfall events has been pre-processed,raindrop size distribution parameters of 3-type rainfalls are comprehensively processed and analyzed,Gamma-distribution function of DSD has been fitted for stratiform,convective and stratocumulus rainfall.In addition,with the DSD data,relationship between fall velocity V and raindrop diameter D and relationship between radar reflectivity factor Z and precipitation intensity R is fitted,Polarimetric parameters and attenuation parameters are calculated,and attenuation correction of C-band radar reflectivity factor is tested and validated.First,the DSD data is filtered and processed.The results show that compared to the unprocessed DSD data,mircophysical parameters calculated with the quality controlled data are closer to the output value of the Parsivel laser spectrometer.The greater the precipitation intensity is,the more obvious the difference between the two is.Secondly,characteristics of microphysical parameters and raindrop size distribution in 3-type rainfalls are analyzed,V-D relationship and Z-R relationship are fitted.In general,big raindrops with diameters between 1mm and 3mm contribute most to radar reflectivity factor in stratocumulus rainfall,while only those drops with diameter bigger than 3mm contribute most in cumulonimbus rainfall.When the precipitation intensity getting stable or larger in the rainfall,the raindrop size distribution mostly shows a multi peak spectrum,otherwise,the raindrop size distribution mostly has a single peak spectrum.The fitting curve of ?-?relationship of a Gamma-distribution DSD gradually rises from stratiform,stratocumulus to convective rainfall,which implies that the relationship is perfect to a specific rainfall situation.The V-D relationship and Z-R relationship of 3-type rainfalls in Nanjing is also fitted.Finally,with DSD data,polarimetric parameters and attenuation parameters are calculated,and attenuation correction of C-band radar reflectivity factor is tested and validated.The results show that the greater the precipitation intensity is,the more obvious the phenomenon of radar echo underestimation is.The reason for the multi-slope of the attenuation factors AH and ADP is the different scales of raindrop.The applications of DSD data in weather radar is tested by the attenuation correction of radar reflectivity factor.