Freezing Nucleus Spectra for Hailstone Samples in China From Droplet Freezing Experiments.

Ice nucleating particles (INPs) can be important for deep convective storms through affecting microphysical, thermodynamical, and radiative properties and precipitation. Since the mass of a hailstone is predominantly contributed by supercooled cloud droplets, INPs in supercooled cloud droplets during deep convective storms can be indicated from INPs in hailstones. In this study, hailstones are collected from eight deep convective cases in three regions of China, and immersion freezing INPs in hailstones are measured using droplet freezing experiments over a wide temperature range from −27.5°C to −4.0°C. INP concentrations can vary by 2–3 orders of magnitude, which is consistent with the result in a previous study on hailstones for the same eight cases that insoluble aerosol number concentrations in hailstones also have a variability of 2–3 orders of magnitude. Using the fitting method, three INP modes are suggested to be included for most hailstone samples, while one to two INP modes can be good enough for a couple of hailstone samples. Furthermore, the INPs for warmer mode are more heat‐sensitive, indicating possible existence of proteinaceous biological species. Plain Language Summary: Ice nucleating particles (INPs) are a small portion of aerosols that can initiate ice crystals at temperatures between −38°C and 0°C in the atmosphere. The knowledge of INPs immersed in hailstones is helpful for understanding the heterogeneous ice production process during deep convective storms. This study measures immersion freezing INPs in hailstones collected from eight deep convective storm cases using droplet freezing experiments. Over the experiment temperature range from −27.5°C to −4.0°C, the variability of INP concentrations can be 2–3 orders of magnitude. Through further investigation of freezing nucleus spectra, three INP modes are suggested to be the best description of INP concentrations for most hailstone samples. Indications are found that INPs for warmer mode are more likely to be proteinaceous biological species. Key Points: Over a wide temperature range from −27.5°C to −4.0°C, ice nucleating particle concentrations for hailstones in China are measuredBest fitting of ice nucleating particle concentrations over the experiment temperature range suggests three modes for most hailstonesIce nucleating particles are heat‐sensitive at high temperatures, indicating the existence of proteinaceous biological species [ABSTRACT FROM AUTHOR]