Analysis of a Hail Process in Foshan, Guangdong Province, Using an Advanced Phased-Array Radar System and Development of a New Warning Index

Dual-Doppler radar detection and wind-field retrieval techniques are crucial for capturing small-scale structures within convective systems. The spatiotemporal resolution of radar data is a key factor influencing the accuracy of wind-field observations. Recently, an advanced X-band phased-array weather radar system was deployed in Foshan, Guangdong Province. This system comprises a central collaborative control unit and multiple networked phased-array radar frontends. These radar frontends work together to scan a common area, achieving a maximum data time difference of 5 s and a volume scan interval of 30 s, thus providing a higher spatiotemporal resolution and more accurate three-dimensional wind-field data than traditional methods. This study utilized an X-band phased-array weather radar system to analyze development of a significant hail cloud in Foshan on March 26, 2022. S-band weather radar data indicated that hail cloud activity significantly intensified after 14:42, with the maximum reflectivity factor exceeding 60 dBZ above the -20 °C altitude layer, and reflectivity continued to increase over the subsequent 12 min. More precise flow-field structure information of the storm was obtained using the X-band phased-array weather radar system. This study analyzed temporal and vertical variations in the maximum reflectivity factor, updraft velocity, vertical wind shear, and horizontal wind speed within a hail cloud. The results showed that the height, intensity, and range of the main updraft area increased as the storm core ascended. Concurrently, the vertical wind shear in the mid‒lower levels of the storm became more pronounced as the height of the strong radar echo center increased prior to the peak of the updraft. Based on these observations, a new hail warning index was developed using vertical wind shear, which can issue warnings up to 12 min earlier than traditional methods for detecting increases in hailstorm intensity.