Abstract:A localized severe convective rainfall event that occurred in east Sichuan Basin under the background of southwest vortex on 8 August 2021 is analyzed by using the Chongqing S-band dual-polarization radar data, ERA5 reanalysis data and multi-source precipitation product. The results show that at the early developing stage of the convection system, ZH and KDP began to increase. Snow particles played a major role in ice-phase hydrometers at middle-upper level. The proportion of drizzle identification at the low level ranged from 20% to 40%. Raindrops were small and surface hourly rainfall intensity was weak. During the rapid intensification of the convection system, ZH, ZDR and KDP increased rapidly as well. ZDR and KDP columns can extended well above 8 km. Uplifted droplets generated supercooled water, facilitating ice-phase process over the melting layer. The melting of descending ice hydrometeors led to the enhancement of liquid particles’ sizes and concentration at middle-lower level, which intensified the surface hourly rainfall intensity. Convective cells were merged with each other and shifted eastward subsequently. As the system weakened, dry and wet snow particles became the main components of ice-phase particles at middle-upper level again. Both size and number of liquid particles at middle-lower level decreased and surface hourly rainfall intensity got weakened accordingly. Dual-polarization variables and hydrometeor identification can basically reflect the characteristic of hydrometeor transformation within the convection systems and cohere reasonably with the variation of surface hourly rainfall intensity.