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.