Abstract:The hailstorm process in Nanjing on 28 April 2015 is analyzed by using microwave radiometer, wind profiling radar, laser precipitation particle spectrometer and other automatic observation data. The results show that: (1) The combination of cold air associated with cold vortex over North China stretching towards the south and lower level moisture air was found to be the circulation background of the severe hailstorm in Nanjing. The transportation of upper level cold advection and lower level warm advection strengthened the formation of the extreme unstable atmosphere stratification. The lasting of surface medium scale convergence center and convergence line played the triggering role in the hail weather. (2) In the hail clouds, strong updraft transport of low level air sensible heat and latent heat led to significant increase of ambient temperature above 2 km altitude observed by microwave radiometer. When the hailstorm was in progress, continuous convergence of low level moisture air and the hail fell into the melting area, causing an increase in low level relative humidity and vapor density. Integrated liquid water (ILW) showed doublepeak structure. When the hailstorm process was initiated, ILW increased rapidly and reached maximum, which indicates the beginning of severe convective weather. (3) Comparing wind profile radar products in 3 stations, various vertical wind fields were observed in different regions. The hailstorm process in Luhe was closely related to the deep vertical wind shear at 0-6 km and the upper level jet stream, incorporating with the mesoscale cyclone on the ground and middle level mesocyclone, which made the hail process very intensive. The east movement of trough in lower troposphere was observed when Nanjing was hailing, while the vertical wind shear at lower level forced continuous hail shooting at Gaochun. The conclusion makes a further understanding of environment condition about vertical structure during this heavy hailstorm event. (4) The micro structure characteristics of the precipitation at Luhe and Gaochun is discussed by using the laser precipitation spectrometers. The different droplet spectra characteristics corresponding with different precipitation types, the raindrop size distribution pattern in two stations basically showed the form of exponential distribution and multi peak structure respectively. Gaochun monitored hail with maximum diameter of 15 mm and Luhe was 5 mm. The raindrop velocity distribution both showed single peak type, and the terminal speed of particles during the severe raining period was between 2 and 5 m·s-1. (5) The severe hail supercell storm at Luhe showed typical features of hook shaped echo, suspended high strong echo area and TBSS.