Role of Aerosol Ice‐Nucleus Effect in the Development of the “21⋅7” Henan Extreme Precipitation

Abstract The aerosol ice‐nucleus (IN) effect, affecting heterogeneous ice nucleation and ultimately shaping cloud properties and precipitation efficiency, remains poorly understood and is overlooked in most operational numerical weather models. Therefore, this study aims to investigate the role of aerosol IN effect in the “21⋅7” Henan extreme precipitation event using two simulations based on an aerosol‐aware configuration of the WRF model. One prescribed spatially uniform ice nucleation particles (INP) concentration (labeled CTL), whereas the other incorporated MERRA2 aerosol concentration fields to represent a more realistic INP spatial distribution (labeled M2), which is marked by a west‐east gradient with higher INP concentration in the west. Results show that M2 simulated heavier precipitation near Zhengzhou closer to the observation regarding both spatial distribution and intensity than the CTL simulation. This improvement is attributed to an INP‐induced feedback akin to the aerosol lifetime effect. Specifically, the M2 simulation had higher INP concentration in the west, causing increased rates of heterogeneous ice nucleation as the convection progressed from west to east. This released additional latent heat, intensifying the convection and subsequently enhancing homogeneous ice nucleation, yielding more but smaller cloud ice particles in M2. These ice particles had reduced sedimentation speeds and lower aggregation rates, suppressing precipitation upstream of Zhengzhou. The intensified convection, carrying more water, propagated eastward, ultimately resulting in extremely heavy precipitation near Zhengzhou. This study underscores the aerosol IN effect on cloud microphysics, convection intensity, and regional rainfall distribution, elucidating the crucial role of aerosol‐meteorology coupling in accurately simulating moderate deep convective cloud precipitation.