Secondary new particle formation in Northern Finland Pallas site between the years 2000 and 2010 1Finnish Meteorological Institute, Erik Palménin aukio 1, 00560 Helsinki, Finland
20 Dec 2011
*currently at: Laboratoire de Météorologie Physique, Université Blaise Pascal, Clermont-Ferrand, UMR6016, France
Received: 11 Sep 2011 – Published in Atmos. Chem. Phys. Discuss.: 15 Sep 2011 Abstract. Secondary new particle formation affects atmospheric aerosol and cloud
droplet numbers and thereby, the aerosol effects on climate. In this paper,
the frequency of nucleation events and the associated particle formation and
growth rates, along with their seasonal variation, was analysed based on over
ten years of aerosol measurements conducted at the Pallas GAW station in
northern Finland. The long-term measurements also allowed a detailed
examination of factors possibly favouring or suppressing particle formation.
Effects of meteorological parameters and air mass properties as well as
vapour sources and sinks for particle formation frequency and event
parameters were inspected. In addition, the potential of secondary particle
formation to increase the concentration of cloud condensation nuclei (CCN)
sized particles was examined. Findings from these long-term measurements
confirmed previous observations: event frequency peaked in spring and the
highest growth rates were observed in summer, affiliated with increased
biogenic activity. Events were almost exclusively observed in marine air
masses on sunny cloud-free days. A low vapour sink by the background particle
population as well as an elevated sulphuric acid concentration were found to
favour particle formation. These were also conditions taking place most
likely in marine air masses. Inter-annual trend showed a minimum in event
frequency in 2003, when also the smallest annual median of growth rate was
observed. This gives further evidence of the importance and sensitivity of
particle formation for the condensing vapour concentrations at Pallas site.
The particle formation was observed to increase CCN80 (>80 nm
particle number) concentrations especially in summer and autumn seasons when
the growth rates were the highest. When the growing mode exceeded the
selected 80 nm limit, on average in those cases, 211 ± 114%
increase of CCN80 concentrations was observed.
Revised: 30 Nov 2011 – Accepted: 13 Dec 2011 – Published: 20 Dec 2011
Citation: Asmi, E., Kivekäs, N., Kerminen, V.-M., Komppula, M., Hyvärinen, A.-P., Hatakka, J., Viisanen, Y., and Lihavainen, H.: Secondary new particle formation in Northern Finland Pallas site between the years 2000 and 2010, Atmos. Chem. Phys., 11, 12959-12972, doi:10.5194/acp-11-12959-2011, 2011.