Seasonal variations in physical characteristics of aerosol particles at the King Sejong Station, Antarctic Peninsula

Abstract

Abstract. Seasonal variability in the physical characteristics of aerosol particles sampled from the King Sejong Station in the Antarctic Peninsula was investigated over the period between March 2009 and February 2015. Clear seasonal cycles for the total particle concentration (CN) were observed. The mean monthly concentration of particles larger than 2.5 nm (CN 2.5 ) was highest during the austral summer, with an average value of 1080.39 ± 595.05 cm −3 , and lowest during the austral winter, with a mean value of 197.26 ± 71.71 cm −3 . The seasonal patterns in the concentrations of cloud condensation nuclei (CCN) and CN coincide, with both concentrations being at a minimum in winter and maximum in summer. The measured CCN spectra were approximated by fitting a power-law function relating the number of CCN for a given supersaturation (SS) to each SS value, with fitting coefficients C and k T . The values for C varied from 6.35 to 837.24 cm −3 , with a mean of 171.48 ± 62.00 cm −3 . The values for k T ranged from 0.07 to 2.19, with a mean of 0.41 ± 0.10. In particular, the k T values during the austral summer were higher than those during the winter, indicating that aerosol particles are more sensitive to SS changes during summer. Furthermore, the annual mean hygroscopicity parameter, κ, was estimated as 0.15 ± 0.05, for a SS of 0.4 %. The effects of the origin and pathway travelled by the air mass on the physical characteristics of the aerosol particles were also determined. The modal diameter of aerosol particles originating in the South Pacific Ocean showed a seasonal variation varying from 0.023 µm in winter to 0.034 µm in summer for the Aitken mode, and from 0.086 µm in winter to 0.109 µm in summer for the accumulation mode.

High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWARE

“…Previous observations at a site 10 km from McMurdo Station showed an increase in the fraction of CN smaller than 250 nm at polar sunrise (September-October), although a specific cause was not clear (Giordano et al, 2017). The higher CCN / CN ratio in the summer (Table 1) is consistent with both the higher biogenic sulfate contributions during the highest productivity season (summer) and the slightly larger diameter of the accumulation mode particles observed in previous summers (Kim et al, 2017).…”

“…S5), with values of 1.5 ± 0.3 for growth factors and 0.4 ± 0.1 for hygroscopicity parameters. These numbers were constant across the measured size range of 50 to 250 nm diameter and are comparable to other observations in the Antarctic region (Wex et al, 2010;Asmi et al, 2010;Kim et al, 2017). The particles that had hygroscopicity too low to grow measurably may be those that were emitted by local anthropogenic emissions.…”

“…At the South Pole, aerosol particle number concentration ranged from 10 to 30 cm −3 in winter and 100 to 300 cm −3 in summer (Bodhaine, 1983;Parungo et al, 1981;Hogan and Barnard, 1978). This low winter and high summer seasonal difference has also been observed at coastal Antarctic sites, but the average concentrations were typically higher, with summertime concentrations ranging from 300 to 2000 cm −3 and wintertime concentrations from 10 to 200 cm −3 (Kim et al, 2017;Gras, 1993). Consistent with this seasonal difference in particle number concentrations, most summertime non-sea salt sulfate mass concentrations were at least 5 times higher than winter concentrations (Jourdain and Legrand, 2002;Weller and Wagenbach, 2007;Udisti et al, 2012;Legrand et al, 2017a;Asmi et al, 2018), likely because of the contributions from biogenic DMS emissions from the surrounding Southern Ocean.…”

“…Asmi et al (2010) found that aerosol particles over the Southern Ocean are very hygroscopic, with a growth factor of 1.75 at 90 nm. At King Sejong Station on King George Island, Kim et al (2017) found that CCN concentrations are high in summer (∼ 200 cm −3 ) and low in winter (∼ 50 cm −3 ). Biological emissions from marine sulfate sources have been proposed to explain a large fraction of CCN in the Southern Ocean region (McCoy et al, 2015).…”

“…The few year-round aerosol concentration and composition measurements in Antarctica were collected at several sites in coastal Antarctica (all of which are more than 1500 km from McMurdo Station) (Hara et al, 2005;Wagenbach et al, 1998;Jourdain and Legrand, 2002;Gras, 1993;Hara et al, 2004Hara et al, , 2010Weller et al, 2013;Minikin et al, 1998;Read et al, 2008) and at several sites on the Antarctic Peninsula (more than 3000 km from McMurdo Station) (Asmi et al, 2018;Mishra et al, 2004;Kim et al, 2017;Saxena and Ruggiero, 1990;Savoie et al, 1993;Loureiro et al, 1992), as well as at the South Pole (more than 1000 km from McMurdo Station) (Hansen et al, 1988;Bodhaine et al, 1986;Harder et al, 2000;Parungo et al, 1981;Bodhaine, 1983;Hogan and Barnard, 1978) and at Dome C (more than 1000 km from McMurdo Station) (Legrand et al, 2017a, b;Udisti et al, 2012). At the South Pole, aerosol particle number concentration ranged from 10 to 30 cm −3 in winter and 100 to 300 cm −3 in summer (Bodhaine, 1983;Parungo et al, 1981;Hogan and Barnard, 1978).…”