A Hybrid Superdroplet–Bin Microphysics Approach Reveals How Large Salt Particles Trigger Rain in Non‐Precipitating Warm Convective Clouds

Abstract This study develops a Superdroplet‐Bin hybrid microphysics scheme within the Weather Research and Forecasting (WRF) model to investigate hygroscopic seeding of warm convective clouds. The Super‐droplet method describes 3D transport, deliquescence, condensation, and collision‐coalescence growth of seeding agents or solution droplets, while the spectral bin method simulates liquid‐phase processes. Idealized simulations indicate that seeding full‐spectrum salt near cloud base can produce a maximum accumulated precipitation of 11.59 mm in 3 h. Further sensitivity experiments on seeding particle size reveal that rainfall enhancement primarily originates from particles ≥4 μm, with 5 μm yielding the most pronounced effect. This is because particles ≥4 μm can nucleate to form droplets ≥20 μm, shifting collision‐coalescence from the low‐efficiency regime below 20 μm to the high‐efficiency regime between large and drizzle‐sized droplets. The tail and rain‐embryo effects are identified as the dominant mechanisms, competition alone cannot effectively broaden the droplet spectrum or trigger precipitation.