Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö field station

Abstract

Abstract. The LAPBIAT measurement campaign took place in the Värriö SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement campaign, concentrations and fluxes of aerosol particles, air ions and trace gases, paying special attention to an aerosol particle formation event broken by a air mass change from a clean Arctic air mass with new particle formation to polluted one approaching from industrial areas of Kola Peninsula, Russia, lacking new particle formation. Aerosol particle number flux measurements show strong downward fluxes during that time. Concentrations of coarse aerosol particles were high for 1-2 days before the nucleation event (i.e. 28-29 April), very low immediately before and during the observed aerosol particle formation event (30 April) and increased moderately from the moment of sudden break of the event. In general particle deposition measurements based on snow samples show the same changes. Measurements of the mobility distribution of air ions showed elevated concentrations of intermediate air ions during the particle formation event. We estimated the growth rates in the nucleation mode size range. For particles <10 nm, the growth rate increases with size on 30 April. Dispersion modelling made with model SILAM support the conclusion that the nucleation event was interrupted by an outbreak of sulphate-rich air mass in the evening of 30 April that originated from the industry at Kola Peninsula, Correspondence to: T. M. Ruuskanen (taina.ruuskanen@helsinki.fi) Russia. The results of this campaign highlight the need for detailed research in atmospheric transport of air constituents for understanding the aerosol dynamics.

Pan-Arctic aerosol number size distributions: seasonality and transport patterns

“…As modelled, all these processes were most active in the summer months. Their results are consistent with observed Arctic precipitation distributions although there is considerable variability and uncertainty in the precipitation amounts and distributions in the Arctic (Serreze and Hurst, 2000). There is general agreement that most of the Arctic receives more precipitation in summer than in winter, except for the North Atlantic sector (including the Spitzbergen region).…”

“…10 shows that the peak median accumulated precipitation along the 240 h back-trajectories is around August for all sites except for Zeppelin -where this peak is in September (the dark season values at Zeppelin are considerably higher too). This is a couple of months later than the maximum monthly local precipitation (Serreze and Hurst, 2000) -possibly and partly due to the change in the transport patterns (panel (c) in Fig. 10) and the continued melting of the sea ice as well as changes in available moisture as air temperatures and absolute humidity rise.…”

“…3 indicate that during the summer and autumn months the air occasionally becomes highly pristine: when N acc drops below 10 cm −3 at Zeppelin, Nord and Alert, and below 20 cm −3 at Barrow and Tiksi. This coincides with the season of maximum precipitation in the Arctic Basin (Serreze and Hurst, 2000) and implies that enhanced wet deposition is a factor in the removal of accumulation-mode particles from the lower Arctic troposphere. Further discussion on the factors that drive the aerosol annual cycle is provided in Sect.…”

“…This is because the coloured shades cover the area of the full 10-day trajectories, while the newly formed aerosols are likely to grow into cloud condensation nuclei (CCN)-sized particles (> ∼ 70 nm) in a day or two (Dal Maso et al, 2005;Kulmala et al, 2001). At high-latitude sites including the Arctic it may take up to 3 days, due to a mean growth rate of newly formed particles of as low as 1 nm h −1 (Asmi et al, 2016;Kulmala et al, 2004;Ruuskanen et al, 2007;Ström et al, 2009;Tunved et al, 2003), unless close to the surface of the open sea in the Arctic, where such growth may occur over a few hours (Willis et al, 2016). A large part of the area covered by cluster 4 trajectories is where the air mass may have been exposed to marine and coastal precursor gases and where the condensation sinks are small due to low pre-existing particle concentrations, both of which enhance the probability of NPF.…”

Improving the simulation of global aerosol with size-segregated anthropogenic number emissions

“…GAINS underestimated the Aitken mode particle concentrations more heavily than AeroCom, by a factor of two to three in Hyytiälä, Värriö and Kpuszta, suggesting that the higher condensation sink associated with higher accumulation mode particle emissions in GAINS had a significant impact on modeled ultra-fine particle number concentrations. In addition, Hyytiälä and Värriö are regions in which BVOC emissions and clean air are the key influencing factors for new particle formation and particle growth (Ruuskanen et al, 2007;Corrigan et al, 2013;Liao et al, 2014). This was reflected in the model results: particle number size distributions in Hyytiälä and Värriö were quite similar between the two simulations based on different anthropogenic emission data sets.…”