Understanding how aerosol particles interact with atmospheric water is critical to understanding their impact on climate and precipitations. Ice Nuclei Particles (INP) trigger the formation of atmospheric ice crystals at temperatures ranging from -5 °C up to -30 °C. They are challenging to characterize because of their scarceness in the atmosphere and their variability, especially at temperatures warmer than -20 °C. At these temperatures, the aerosol particles of biological origin can contribute significantly to INP number concentration. This study incorporates a series of offline, long-term, size-segregated measurements of INPs, collected at the Puy de Dôme station (PUY, 1465 m a.s.l.). PUY is an ideal place to study INPs concentrations as it is advected by a variety of air masses, with about 20% of them originating in the free troposphere. We measured concentrations of INPs between -5 and -18 °C, with concentrations of 0.001 INP/Lair at the warmest temperatures, and between 0.01 and 0.1 INP/Lair at the coldest temperatures. We observe that the majority of INP measured at temperatures warmer than -15 °C are heat labile, in line with other studies. We observe a higher contribution of heat labile INPs during the winter and lower ratios in spring. The INP variability was statistically compared with collocated aerosol characterization at the site. INPs were mainly linked to local and marine tracers. We propose a new parameterization using the total number of aerosols. This parameterization is optimized for warmer temperature INPs. The parameterization showed good performance when tested on independent data sets

Modeling the shortwave radiation balance over the Southern Ocean region remains a challenge for Earth system models. To investigate whether this is related to the representation of aerosol-cloud interactions, we compared measurements of the total number concentration of sea spray generated particles within the Southern Ocean region to model predictions thereof. Measurements were conducted from a container laboratory aboard the R/V Tangaroa throughout an austral summer voyage to the Ross Sea. We used source-receptor modeling to calculate the sensitivity of our measurements to upwind surface fluxes. From this approach, we could constrain empirical parameterizations of sea spray surface flux based on surface wind speed and sea surface temperature. A newly tuned parameterization for the flux of sea spray particles based on the near-surface wind speed is presented. Comparisons to existing model parameterizations revealed that present model parameterizations led to over-estimations of sea spray concentrations. In contrast to previous studies, we found that including sea surface temperature as an explanatory variable did not substantially improve model-measurement agreement. To test whether or not the parameterization may be applicable globally, we conducted a similar regression analysis using a database of in situ whitecap measurements. We found that the key fitting parameter within this regression agreed well the parameterization of sea spray flux. Finally, we compared calculations from the best model of surface flux to boundary layer measurements collected onboard an aircraft throughout the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES), finding good agreement overall.