Unraveling Ice Nucleating Particle Concentration Variability: Insights Into Source Emissions Origin and Parameterizations

Abstract Despite having very low atmospheric concentrations, ice‐nucleating particles (INPs) play an important role in the formation of atmospheric ice crystals at temperatures warmer than −35°C and hence in the atmospheric precipitation cycle. Moreover, they tend to have a very high spatiotemporal variability. In order to understand this variability, long‐term measurements with high temporal resolution are essential. This paper presents an analysis of 3 months of online INP measurements (10 min time‐resolved), using a PINE cloud chamber (−33°C ≤ T ≤ −22°C). Measurements were made from December 2022 to March 2023 at the PUY station (France, 1,465 m a.s.l), a site exposed to a variety of air masses including free troposphere conditions. A large part of the temporal variability of INP concentrations (over four orders of magnitude at a single temperature) can be explained by air mass origin. INP concentrations measured for oceanic air masses are in the lower range (from ≈0.1 to ≈10 L −1 ). Those for continental air masses are in a medium range (from ≈1 to ≈100 L −1 ) and depend on the level of pollution of the air mass. INP concentrations measured for southern air masses show highest concentrations (from ≈10 to ≈500 L −1 ) and mostly depend on the amount of dust in the ambient air. Moreover, measurements were conducted during two dust events revealing INP concentrations over 1000 L −1 at −32°C. Subsequently, a set of parameterizations capable of tracing the measured INP variability were developed. This will facilitate our understanding of the impact of INP concentrations on mixed‐phase cloud properties with cloud models.