Cold Air Outbreaks Promote New Particle Formation off the U.S. East Coast

New particle formation is the dominant contributor to total particle number concentration and plays an important role in the cloud condensation nuclei (CCN) budget. The frequency, intensity, and duration of new particle formation events vary greatly, and the prediction of these events requires improvement. This study uses Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) data to address new particle formation features, including seasonal and spatial statistics, in addition to influential factors in and around clouds, including in postfrontal conditions associated with cold air outbreaks. During winter, higher ratios between particle concentrations greater than 3 nm and 10 nm (N3/N10) were observed compared to summer, especially above boundary layer cloud tops. Cold and dry air, low aerosol surface area concentration, and transport of precursor gases from the continent facilitate new particle formation over the ACTIVATE region, conditions of which are especially prevalent during flights coinciding with cold air outbreaks. Our study serves as a basis for future detailed new particle formation work over the ACTIVATE region to formulate even more robust conclusions.