Multiseasonal measurements of ice-nucleating particle (INPs) levels and their drivers in the Easter Mediterranean during the CHOPIN field campaign

Ice formation in mixed-phase clouds is a critical component of their evolution and impacts on the hydrological cycle and climate. Nevertheless, their quantification and link to different aerosol sources (dust, biological particles) and impact of atmospheric aging leads to considerable uncertainty in their description in atmospheric models. Observations at high altitude mountaintop sites can provide a way to alleviate this uncertainty, as observations can be carried out for extensive periods of time, and can sample both free tropospheric and boundary layer air from a variety of sources and over different seasons – and their associated INP levels. Motivated by the above, we conducted the long-term observation at the top of the Mount Helmos (2314 m above sea level) for 6 months during the Cleancloud Helmos OrograPhic sIte experimeNt (CHOPIN) champaign, as part of the CleanCloud project. The INP concentrations were observed using a Portable Ice Nucleation Experiment (PINE) at -15°C and -25°C. We will discuss the characterization and drivers of INP changes between -15°C and -25°C, as well as cloud events and seasonal variations during fall, winter, and early spring. Additionally, we will discuss the controlling factors for INP activation in combination with other concurrent observations such as aerosol size distribution, fluorescent particle concentrations and shape, biological particle concentrations and speciation (e.g., flow cytometry) and laser remote sensing (elastic-Raman-fluorescence lidar), backtrajectory analysis, and in-situ aerosol chemical composition. We will evaluate the ability of existing parameterizations to capture the INP levels – and their link to aerosol type and origin – and examine whether aged INP (characterized by their airmass type, and acidity levels) tend to exhibit different INP activity compared to more freshly emitted particles.