Aerosol characteristics of air masses in northern Europe: Influences of location, transport, sinks, and sources

Abstract

Synoptic‐scale air masses at different stations were classified following a definition based on Berliner Wetterkarte. This air mass classification has been related to 1 year of aerosol number size distributions measurements performed at four different stations extending from Aspvreten in Sweden (58.8°N) to Pallas in northern Finland (68°N). The air mass classification describes both class of air mass, based on the origin of the air mass, and character of air in terms of marine, mixed, and continental air masses. The aerosol size distribution properties were evaluated in relation to the air masses. Emphasis was put on the differences between marine, mixed, and continental character air masses. It is shown that continental air masses exceed marine and mixed character air masses both in number and mass concentration. Different classes of air masses were further associated with different aerosol size distribution properties. It is also shown that although serving as a somewhat good qualifier for the aerosol at individual stations, the air mass classification cannot be used to estimate the aerosol burden over large geographical areas. Instead, a sharp gradient was shown to exist between different stations, although aerosol properties were observed in equal air masses according to the definition by Berliner Wetterkarte. This gradient manifests as a south‐northerly decrease in aerosol total number and volume, indicating that the aerosol properties including the aerosol size distribution are less conservative than the thermodynamic properties (e.g., pseudo‐potential temperature and humidity profiles) that characterize the different air masses. Further, using a pseudo‐Lagrangian approach, the aerosol turnover time was estimated for different sized aerosols in air moving from south to north (i.e., depletion of aerosols in air arriving from the continent). Turnover time of Aitken particles was found to be in the range of 1–2 days, while accumulation mode turnover time was estimated to be in the order of 2–3 days.