Abstract:Radar data features and hail warning are investigated through differential reflectivity (ZDR) and cold-layer composite differential reflectivity (CZDRC) on the basis of three hail cases observed in Shandong Province in recent years. The results indicate that even when the radar echo area is relatively small, a 3 dB ZDR column feature can be observed within the cloud near the hailfall spots in the CZDRC chart. The ZDR column appears 20-40 min before the first hailfall time during a hail event, which is 10-20 min earlier than the traditional 45 dBz or 55 dBz reflectivity factor threshold, indicating its potential as an early warning indicator for hail. Weather radars of different wavelengths and scanning systems, including X-band dual-polarization phased-array radar, S-band, and C-band radars, present the ZDR column feature necessary for severe convective weather warnings in both the CZDRC chart and ZDR echo area time-height plot. Additionally, the ZDR column feature on the CZDRC chart is closely situated, surrounding the hailfall spots in all three studycases. These ZDR column features are located northwest of the hailfall spots, which are in the mid-tropospheric upwind direction, and could serve as a reference for forecasting and warning of hailfall locations.