Characteristics of atmospheric ice nucleating particles over East Antarctica retrieved from the surface snow.

The concentration of ice nucleating particles (INPs) in the atmosphere is critical for understanding cloud microphysics and predicting the climate system. In this study, we collected surface snow samples along a traverse route from the coastal to the inland of East Antarctica to analyze INP concentrations and identify their spatial variations using a droplet freezing device. The overall concentration of INPs was found to be considerably low along the route, averaging at 0.8 ± 0.8 × 105 L-1 in water and 4.2 ± 4.8 × 10-3 L-1 in air at -20 °C. Although coastal areas had higher levels of sea salt species compared to inland regions, the concentration of INPs remained consistent along the route suggesting less important origination of INPs from the around ocean. Additionally, the heating experiment revealed the important contribution of proteinaceous INPs indicating the presence of biological INPs (bio-INPs). The fraction of bio-INPs was 0.52 on average at -20 °C and ranged from 0.1 to 0.7 from -30 °C to -15 °C. Finally, we parameterize the atmospheric INP concentrations as a function of freezing temperature which can be useful for modeling INP concentrations in this region.