Interannual and interseasonal variabilities and sources of ice nucleating particles in the Arctic

Primary ice formation on the ice nucleating particles (INPs) regulates the Arctic mixed-phase cloud properties and lifetime and thus plays an important role in the Arctic surface energy budget and regional climate. However, the current understanding of Arctic INP sources and overall abundance is so inadequate that we suffer from climate model bias of INP number concentrations. Particularly, the interannual and interseasonal variabilities of Arctic INPs are unclear due to a lack of long-term measurements in the Arctic, which motivates our study. Here, we compare the simulated INP concentrations from the Energy Exascale Earth System Model version 1 (E3SMv1) with long-term ground-level INP measurements made by analyzing aerosol particle samples from Ny-Ålesund. The INP measurements are conducted using an offline immersion freezing assay system called West Texas Cryogenic Refrigerator Applied to Freezing Test. The dataset covers the time period intermittently but various seasons from 2017 to 2021, which provides insight into the interannual and interseasonal variabilities of the Arctic INP concentrations. For the model simulation, various ice nucleation parameterizations are used to include the INP source contribution from dust, black carbon, organics, and sea spray aerosols. The simulated aerosol composition is compared with that derived from filter-based chemical analysis. The simulated aerosol size distributions are also evaluated against measurements from the Scanning Mobility Particle Sizer and the Aerodynamic Particle Sizer. Moreover, the model performance in simulating meteorological conditions is examined. Our preliminary results indicate that local terrestrial and marine sources contribute more to the summertime INP, while springtime INP is dominated by long-range transport aerosol in this Atlantic sector of the Arctic.