Numerical Simulation Study of a Summer Convective Precipitation Event in Hainan

This study employed data from surface automatic weather stations, S-band Doppler radar, and the NCEP Final (FNL) operational global analysis, together with the mesoscale Weather Research and Forecasting (WRF) model, to analyze and simulate a convective precipitation event that occurred over Hainan Province on 17 August 2024. The evolution of precipitation and its dynamic and microphysical structures were examined. The results showed that this precipitation process was mainly influenced by the combined effects of a deep low-pressure system in the north and the subtropical high. These systems were accompanied by a low-level southwest jet that provided abundant water vapor and created an unstable atmospheric stratification. These conditions were conducive to the formation and development of heavy precipitation. The numerical model reproduced this convective precipitation process well. The autoconversion of cloud water into rainwater and the collision–coalescence between cloud water and rainwater accounted for 63% of the rainwater source, while the melting of graupel and snow to rainwater contributed only 24%. During the event, the precipitation efficiency was only 48%–65%, indicating that the precipitation efficiency of this convective cloud relied more on efficient condensation and collision processes within the low-level warm-cloud region, and the warm-cloud process was the main mechanism of this precipitation. Sensitivity tests using six microphysics schemes consistently showed that warm-cloud processes are significantly stronger than cold-cloud processes, thereby verifying the reliability of the findings. Thus, this study reveals the evolution, dynamics, and microphysical structures of the convective precipitation event in Hainan Province and their link to precipitation efficiency, thereby offering a theoretical basis and reference for improving precipitation forecasts.