Cloud seeding is considered a practical but unproved method to enhance precipitation or suppress hail, due to insufficient knowledge of ice formation and evolution after seeding clouds with ice nucleating particles. This study investigates the size effects on the immersion freezing of aerosol produced from commercial silver iodide (AgI) containing flares at mixed-phase cloud temperatures from 243 to 267 K. Flare-generated aerosol exhibited comparable ice nucleation ability (INA) to pure AgI particles in the size range of 200 and 400 nm. Non-AgI impurities reduced the INA of flare-generated particles ≤90 nm, which is lower than pure AgI particles ≤40 nm. The critical mass ice-active site density of the generated aerosols (critical-n_m) was derived, indicating the minimum mass of AgI particles required for efficient ice nucleation. The new parameterization to predict critical-n_m can serve as a reference to optimize the effectiveness of cloud-seeding materials for practical use.

中文翻译：

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含碘化银冰川云播种颗粒的临界尺寸

人工播种被认为是一种实用但未经证实的增强降水或抑制冰雹的方法，因为对用冰核颗粒播种云后冰的形成和演化了解不够。本研究调查了在 243 至 267 K 的混合相云温度下，商业碘化银 (AgI) 产生的气溶胶对浸入式冷冻的影响。耀斑产生的气溶胶表现出与纯 AgI 颗粒相当的冰成核能力 (INA)。尺寸范围为 200 至 400 nm。非 AgI 杂质降低了耀斑产生的颗粒 ≤90 nm 的 INA，低于纯 AgI 颗粒 ≤40 nm。得出了_所产生气溶胶的临界质量冰活性位点密度（临界- nm），表明有效冰成核所需的 AgI 颗粒的最小质量。预测临界nm的新参数化可以作为优化实际使用的播云材料有效性的参考_。