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  • 1.
    Behrenfeldt, Ulrika
    et al.
    Stockholm Univ, Dept Appl Environm Sci, S-10691 Stockholm, Sweden..
    Krejci, Radovan
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden..
    Ström, Johan
    Stockholm Univ, Dept Appl Environm Sci, S-10691 Stockholm, Sweden..
    Stohl, Andreas
    NILU, Norwegian Inst Air Res, Kjeller, Norway..
    Chemical properties of Arctic aerosol particles collected at the Zeppelin station during the aerosol transition period in May and June of 20042008In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 60, no 3, p. 405-415Article in journal (Refereed)
    Abstract [en]

    Single particle analysis was performed on samples taken at the Zeppelin Station, Svalbard, during the ASTAR campaign, 2004. Thirteen samples were selected to representatively cover the campaign period and different weather conditions. This particular period also covers the transition from an accumulation mode dominated size distribution in spring to an Aitken mode dominated aerosol size distribution in summer. Altogether, 1353 particles were analysed and their elemental composition documented. Another 1225 were counted but not characterized chemically. The samples were compared with respect to chemical composition, aerosol size, shape and airmass origin. The comparison showed that the samples taken before the aerosol size transition were dominated by spherical 'organic like' particles in the submicrometre range, with an Eurasian influence. The samples taken after the size transition showed a more complex character and the source origin was the Arctic basin. In this period, an increase of both marine aerosol groups as well as groups of continental origin became more pronounced. This apparent contradiction may have its explanation in cloud scavenging processes, removing the hygroscopic particles from the old continental air, leaving the more hydrophobic particles, at the same time, as the ocean source will provide a more maritime character.

  • 2.
    Engvall, Ann-Christine
    et al.
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden..
    Krejci, Radovan
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden..
    Ström, Johan
    Univ Stockholm, Atmospher Sci Unit, Dept Appl Environm Sci, S-10691 Stockholm, Sweden..
    Minikin, Andreas
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Atmospher Phys, D-82234 Oberpfaffenhofen, Wessling, Germany..
    Treffeisen, Renate
    Alfred Wegener Inst Polar & Marine Res, D-14473 Potsdam, Germany..
    Stohl, Andreas
    Norwegian Inst Air Res, N-2027 Kjeller, Norway..
    Herber, Andreas
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    In-situ airborne observations of the microphysical properties of the Arctic tropospheric aerosol during late spring and summer2008In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 60, no 3, p. 392-404Article in journal (Refereed)
    Abstract [en]

    In-situ aerosol data collected in the Arctic troposphere during a three-week period in 2004 were analysed. The measurements took place during late spring, i.e., at the time of the year when the characteristics of the aerosol distribution change from being accumulation-mode dominated to being primarily of the Aitken-mode type, a process that previously has been observed in the boundary layer. To address the question whether this transition is also detectable in the free troposphere of an aircraft-measured data from the ASTAR 2004 campaign were analysed. In this study, we present vertically as well as temporally results from both ground-based and airborne measurements of the total number concentrations of particles larger than 10 and 260 nm. Aircraft-measured size distributions of the aerosol ranging from 20 to 2200 nm have been evaluated with regard to conditions in the boundary layer as well as in the free troposphere. Furthermore an analysis of the volatile fraction of the aerosol population has been performed both for the integrated and size-distributed results. From these investigations we find that the transition takes place in the entire troposphere.

  • 3.
    Engvall, Ann-Christine
    et al.
    Norwegian Inst Air Res NILU, N-2027 Kjeller, Norway..
    Ström, Johan
    Norwegian Polar Res Inst, N-9296 Tromso, Norway..
    Tunved, Peter
    Stockholm Univ, Dept Appl Environm Sci, Atmospher Sci Unit, S-10691 Stockholm, Sweden..
    Krejci, Radovan
    Stockholm Univ, Dept Appl Environm Sci, Atmospher Sci Unit, S-10691 Stockholm, Sweden..
    Schlager, Hans
    Inst Phys & Atmosphare, Deutsch Zentrum Luft & Raumfahrt, D-82234 Oberpfaffenhofen, Wessling, Germany..
    Minikin, Andreas
    Inst Phys & Atmosphare, Deutsch Zentrum Luft & Raumfahrt, D-82234 Oberpfaffenhofen, Wessling, Germany..
    The radiative effect of an aged, internally mixed Arctic aerosol originating from lower-latitude biomass burning2009In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 61, no 4, p. 677-684Article in journal (Refereed)
    Abstract [en]

    Arctic-haze layers and their radiative effects have been investigated previously in numerous studies as they are known to have an impact on the regional climate. In this study, we report on an event of an elevated aerosol layer, notably consisting of high-absorbing soot particles, observed in the European Arctic free troposphere the 2007 April 14 during the ASTAR 2007 campaign. The ca. 0.5 km vertically thick aerosol layer located at an altitude of around 3 km had a particle-size distribution mode around 250 nm diameter. In this study, we quantify the radiative effect aerosol layers have on the Arctic atmosphere by using in situ observations. Measurements of particles size segregated temperature stability using thermal denuders, indicate that the aerosol in the optically active size range was chemically internally mixed. In the plume, maximum observed absorption and scattering coefficients were 3 x 10(-6) and 20 x 10(-6) m(-1), respectively. Observed microphysical and optical properties were used to constrain calculations of heating rates of an internally mixed aerosol assuming two different surface albedos that represent snow/ice covered and open ocean. The average profile resulted in a heating rate in the layer of 0.2 K d(-1) for the high-albedo case and 0.15 K d(-1) for the low albedo case. This calculated dependence on albedo based on actual observations corroborates previous numerical simulations. The heating within the plume resulted in a measurable signal shown as an enhancement in the temperature of a few tenths of a degree. Although the origin of the aerosol plume could not unambiguously be determined, the microphysical properties of the aerosol had strong similarities with previously reported biomass burning plumes. With a changing climate, short-lived pollutants such as biomass plumes may become more frequent in the Arctic and have important radiative effects at regional scale.

  • 4.
    Ström, Johan
    et al.
    Stockholm Univ, Dept Appl Environm Sci, S-10691 Stockholm, Sweden.;Norwegian Polar Res Inst, N-9296 Tromso, Norway..
    Engvall, Ann-Christine
    Norwegian Inst Air Res, NILU, N-2027 Kjeller, Norway..
    Delbart, Frank
    IPEV French Polar Inst, CNRS, F-29280 Plouzane, France..
    Krejci, Radovan
    Norwegian Inst Air Res, NILU, N-2027 Kjeller, Norway..
    Treffeisen, Renate
    Alfred Wegener Inst, D-14473 Potsdam, Germany..
    On small particles in the Arctic summer boundary layer: observations at two different heights near Ny-Alesund, Svalbard2009In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 61, no 2, p. 473-482Article in journal (Refereed)
    Abstract [en]

    Concurrent observations of particle number densities and size distributions observed at two different heights (near ocean level and 475 m above sea level) in Ny-Alesund, Svalbard were studied with respect to the diurnal variation during a summer period in June 2004. The results show that observed variation in particle number density in the Arctic boundary layer may be strongly modulated by vertical mixing and dilution. The particles appeared to be formed in the early morning when solar intensity reached about 30% of the mid-day intensity. Based on differences in the observed number densities at the two heights it appears as if particles are formed in the lower part of the boundary layer. The formation rate of 10 nm diameter particles is estimated to be 0.11 cm(-3) s(-1) and the growth rate is in a range between 1 and 2 nm h(-1).

1 - 4 of 4
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