Changes in aerosol properties during spring-summer period in the Arctic troposphere

Abstract

Abstract. The change in aerosol properties during the transition from the more polluted spring to the clean summer Arctic troposphere was studied. A six year data set of observations from Ny-Ålesund, Svalbard, covering the months April through June serve as the basis for the characterisation of this time period. In addition four-day-back trajectories were used to describe air mass histories. The observed transition in aerosol properties from an accumulation mode dominated to an Aitken mode dominated size distribution is discussed with respect to long-range transport and influences from natural and anthropogenic sources of aerosols and pertinent trace gases. Our study shows that the air-mass transport is an important factor modulating the physical and chemical properties observed. However, the air-mass transport cannot alone explain the yearly repeatable systematic and rather rapid change in aerosol properties, occurring within a limited time window of approximately 10 days. With a simplified phenomenological model, which delivers the nucleation potential for new particle formation, we suggest that the rapid shift in aerosol microphysical properties between the Arctic spring and summer is mainly driven by the incoming solar radiation in concert with transport of precursor gases and changes in condensational sink.