Influence of Radar Data Cycling Assimilation on Thunderstorm Gale Simulation in Nantong on April 30, 2021

Using Doppler weather radar, ERA5 reanalysis, and ground automatic station observation data, numerical simulations of a thunderstorm gale process in Nantong, Jiangsu Province, on April 30, 2021, were performed using the Weather Research and Forecasting model, radar radial wind quality control, and GSI (Gridpoint Statistical Interpolation) cycle assimilation. The spatiotemporal evolution and structural characteristics of radar reflectivity, wind field, and thermal dynamics simulated by various experimental schemes were compared and examined. Results revealed that the cycling assimilation scheme (Exp3) with an assimilation interval of 30 min has substantially enhanced the simulation results compared with the nonassimilated and nonadjacent cycling assimilation schemes, demonstrating that cycling assimilation and increased frequency effectively improve the initial field. The UNRAVEL dealiasing algorithm effectively eliminates the velocity ambiguities and enhances the initial field in the cycling assimilation scheme (Exp4) after radar data processing using dealiasing, resulting in substantial adjustments in the simulated radar reflectivity and surface wind fields for this thunderstorm wind event. The corresponding features and evolving trends align with the observations, indicating that the cycling assimilation scheme with UNRAVEL dealiasing is more effective in improving the initial field. Based on the results of the thermodynamic field, the dynamic and thermal structures of the Exp4 scheme are prominently improved with upper-level divergence and lower-level convergence and a “cold–warm–cold” thermodynamic structure. This structure is accompanied by strong upward motion, high pressure distribution in the north and low pressure distribution in the south, and strong vertical wind shear, which helps transfer the horizontal momentum from the mid-high level to the near-surface layer through the sinking airflow, thereby provoking this thunderstorm gale event.