Frequent occurrence of newly formed aerosol particles over wide geographical areas in the Arctic free troposphere and atmospheric boundary layer

Abstract. New particle formation (NPF) can impact the Arctic radiative energy budget since this region is particularly sensitive to changes in aerosol particle and cloud condensation nuclei concentrations. Prior studies have predominantly investigated NPF in the Arctic atmospheric boundary layer (ABL), concluding that this phenomenon primarily takes place close to the surface. However, this study shows that NPF may take place throughout the entire lower Arctic troposphere. We have reached this conclusion by analyzing particle number size distribution data collected during a springtime aircraft campaign in the vicinity of Svalbard, the Fram Strait, and northern Greenland. We detected newly formed aerosol particles at various altitudes ranging from about 60 m to 3900 m and identified three atmospheric scenarios for their occurrence: newly formed particles in the free troposphere, in the ABL over sea ice, and in the vicinity of clouds. Our results suggest that regional Arctic atmospheric processes as well as long-range transport play key roles in the formation of new particles. Based on our data, we furthermore conclude that NPF may be a frequent and geographically extended phenomenon in the Arctic free troposphere.