Convective Structure and Microphysical Characteristics of a Cold-season Elevated Hailstorm on 21 February 2024

Multi-source observational datasets, including high-frequency, minutely automatic weather stations, an X-band phased-array radar, a wind profiler radar and a microwave radiometer, are employed to analyze a typical cold-season elevated hailstorm occurred over Shanghai on 21 February 2024. The convective system develops approximately 170 km behind a surface cold front, where a stable low-level cold pool coexists with a warm, moist, low to middle-level southwesterly jet, establishing extremely favorable thermodynamic conditions for elevated convection. Prior to hailfall, the wind profiler radar detects a rapid intensification of the low-level jet, accompanied by a significant increase in vertical wind shear between 1.5- and 3-km height, which provides a dynamical environment conducive to organized convective development. Observations from the microwave radiometer reveal an early enhancement of middle to upper-level humidity and liquid water content, indicating persistent warm-moist transport and continuous growth of cloud hydrometeors. The X-band phased-array radar captures high-resolution internal structural and microphysical evolution within the severe storm. During the development stage, prominent Z_DR columns and K_DP columns indicate vigorous updrafts and abundant supercooled water, promoting hail embryo formation. In the mature stage, K_DP holes above 0 ℃ level and high reflectivity extending beyond the -20 ℃ level indicate the generation and subsequent descent of large hail particles. During the dissipation stage, elevated low-level K_DP values coincide with enhanced downdrafts, reflecting hail melting and the gradual collapse of the convective system. The integration of these multi-platform observations provides a comprehensive depiction of the hailstorm's complete life cycle, from environmental setup and warm-moist transport to hail development and storm decay. Each observing platform contributes unique complementary information: The wind profiler characterizes low-level dynamic acceleration and shear evolution; the microwave radiometer traces thermodynamic and water content changes; and X-band phased-array radar resolves high-resolution storm microphysics and structural evolution of the storm. Together, these datasets elucidate the key physical mechanisms driving elevated convection and hail formation in a cold-season setting. The combined use of multi-source observations is shown to be highly valuable for investigating elevated hailstorms, and the operational relevance of such integrated data for monitoring and nowcasting severe convective weather during winter and early spring is highlighted. Findings provide critical insight into storm structure and evolution, offering reliable practical guidance for early warning and risk mitigation in densely populated urban regions.