Concentration of particles larger than 2.5 nm collected during the Arctic Ocean 2018 expedition

The concentration of particles larger than 2.5 nm was measured with an ultrafine condensation particle counter (UCPC). The concentration was corrected for diffusional losses in the inlet based on the neutral cluster and air ion spectrometer (NAIS) size distribution. The concentration and temporal dynamics of small particles is fundamental to characterize the first step of new particle formation (NPF) and growth. Newly formed particles can grow to larger sizes where they act as cloud condensation nuclei, directly affecting the Earth radiative budget and cloud properties. Measurements were performed on the 4th deck of icebreaker Oden during August and September 2018 along the track of the expedition. The concentration is reported as particle per cubic centimeter in 60 seconds average.