A new feedback mechanism linking forests, aerosols, and climate

Self Cite

A B S T R A C T Particle formation events were analysed from aerosol number size distribution data collected at a background station in southern Sweden between February 2001 and May 2004. Events occurred on about 36% of all days and were favoured by high global radiation values. The clearest events (class I, 20% of all days) were observed when the formation rate of activated hypothetical clusters around 1 nm diameter, J 1 was higher than 10 (180 * CondS-0.60) , where CondS is the condensation sink (in s −1 ). The median condensable vapour concentration, observed formation rate at 3 nm, and growth rate during class I events were 3.0 × 10 7 cm −3 , 1.1 cm −3 s −1 and 2.1 nm h −1 , respectively. On 7% of all days, it was possible to observe growth of the newly formed particles exceeding 30 nm geometric mean diameter during event days in the evening, which is important for the regional particle population, and thereby the climate. A trajectory analysis revealed that cleaner air masses were relatively more important for the contribution of Aitken mode particles than polluted ones. Class I events were registered on 36% of all days when trajectories had passed over the open sea, indicating that ship traffic can contribute to particle formation and growth.

Section: Resultssupporting

confidence: 74%

Section: Resultsmentioning

confidence: 71%

Characterization of new particle formation events at a background site in Southern Sweden: relation to air mass history

Kristensson

Maso

Swietlicki

et al. 2008

Self Cite

“…We cannot fully understand the effects of anthropogenic air pollution without knowing the properties of the natural atmosphere (Andreae, 2007). The natural secondary aerosol and its changes with increasing temperature and trends in emissions of biogenic aerosol precursors have been proposed to be a vital part in feedback mechanisms of the climate, via both direct and indirect aerosol effects (Kulmala et al, 2004b). In fact, for the pre‐industrial atmosphere over continental regions, secondary organic aerosol (SOA) have been arguably the chief components of cloud condensation nuclei and, even today, play a major role in that respect over large forested areas like the boreal forest and of the Amazon (Kanakidou et al, 2000; Tunved et al, 2006; Andreae, 2007).…”

Section: Introductionmentioning

confidence: 99%

Aerosol particle formation events and analysis of high growth rates observed above a subarctic wetland–forest mosaic

Svenningsson

Arneth

Hayward

et al. 2008

T E L L U S Aerosol particle formation events and analysis of high growth rates observed above a subarctic wetland-forest mosaic A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern Sweden was performed, based on numbersize distributions of atmospheric aerosol particles (10-500 nm in diameter) and ions (0.4-40 nm in Tammet diameter). We present classification statistics for PF events from measurements covering the period July 2005-September 2006, with a break over the winter period. The PF event frequency peaked during the summer months, in contrast to other Scandinavian sites where the frequency is highest during spring and autumn. Our analysis includes calculated growth rates and estimates of concentrations and production rates of condensing vapour, deduced from the growth rates and condensational sink calculations, using AIS and SMPS data. Particle formation events with high growth rates (up to 50 nm h −1 ) occurred repeatedly. In these cases, the newly formed nucleation mode particles were often only present for periods of a few hours. On several occasions, repeated particle formation events were observed within 1 d, with differences in onset time of a few hours. These high growth rates were only observed when the condensation sink was higher than 0.001 s −1 .

“…The fundamental aerosol and carbon cycle processes need to be understood to quantify aerosol radiative properties and the influence of aerosols on cloud microphysics and dynamics at the scale of individual clouds and to understand changes in carbon uptake dynamics (e.g. Kulmala et al, 2004b). At larger scales, advances in our understanding of boundary layer meteorology are needed to clarify atmospheric aerosol transport, trace gas (e.g.…”

Section: Scientific Approach and Research Methodsmentioning

confidence: 99%

“…We have recently proposed a mechanism coupling the climatic effects of CO 2 and aerosol particles (Kulmala et al, 2004b). This suggestion is based on connections between photosynthesis, emissions of non‐methane biogenic volatile organic compounds (BVOCs), and their ability to form aerosol particles.…”

Section: Background and Objectivesmentioning

confidence: 99%

Overview of the biosphere–aerosol–cloud–climate interactions (BACCI) studies

Kulmala

Kerminen

Laaksonen

et al. 2008

Here we present research methods and results obtained by the Nordic Centre of Excellence Biosphere–Aerosol–Cloud–Climate Interactions (BACCI) between 1 January 2003 and 31 December 2007. The centre formed an integrated attempt to understand multiple, but interlinked, biosphere–atmosphere interactions applying inter and multidisciplinary approaches in a coherent manner. The main objective was to study the life cycle of aerosol particles and their importance on climate change. The foundation in BACCI was a thorough understanding of physical, meteorological, chemical and ecophysiological processes, providing a unique possibility to study biosphere–aerosol–cloud–climate interactions. Continuous measurements of atmospheric concentrations and fluxes of aerosol particles and precursors and, CO2/aerosol trace gas interactions in different field stations (e.g. SMEAR) were supported by models of particle thermodynamics, transport and dynamics, atmospheric chemistry, boundary layer meteorology and forest growth. The main progress was related to atmospheric new particle formation, existence of clusters, composition of nucleation mode aerosol particles, chemical precursors of fresh aerosol particles, the contribution of biogenic aerosol particles on the global aerosol load, transport, transformation and deposition of aerosol particles, thermodynamics related to aerosol particles and cloud droplets, and the microphysics and chemistry of cloud droplet formation.