Natural new particle formation at the coastal Antarctic site Neumayer

Abstract

Abstract. We measured condensation particle (CP) concentrations and particle size distributions at the coastal Antarctic station Neumayer (70°39´ S, 8°15´ W) during two summer campaigns (from 20 January to 26 March 2012 and 1 February to 30 April 2014) and during the polar night between 12 August and 27 September 2014 in the particle diameter (Dp) range from 2.94 to 60.4 nm (2012) and from 6.26 to 212.9 nm (2014). During both summer campaigns we identified all in all 44 new particle formation (NPF) events. From 10 NPF events, particle growth rates could be determined to be around 0.90 ± 0.46 nm h−1 (mean ± SD; range: 0.4–1.9 nm h−1). With the exception of one case, particle growth was generally restricted to the nucleation mode (Dp < 25 nm) and the duration of NPF events was typically around 6.0 ± 1.5 h (mean ± SD; range: 4–9 h). Thus, in the surrounding area of Neumayer, particles did not grow up to sizes required for acting as cloud condensation nuclei. NPF during summer usually occurred in the afternoon in coherence with local photochemistry. During winter, two NPF events could be detected, though showing no ascertainable particle growth. A simple estimation indicated that apart from sulfuric acid, the derived growth rates required other low volatile precursor vapours.

Size distribution and ionic composition of marine summer aerosol at the continental Antarctic site Kohnen

“…As described in Weller et al (2015), NPF events at Neumayer showed generally almost comparable growth rates. Therein we 5 used a simple estimate, based on Nieminen et al (2010) and Yli-Juuti et al (2011) that demonstrated the need of other condensable vapours than sulfuric acid to sustain the observed particle growth (Weller et al, 2015).…”

“…Therein we 5 used a simple estimate, based on Nieminen et al (2010) and Yli-Juuti et al (2011) that demonstrated the need of other condensable vapours than sulfuric acid to sustain the observed particle growth (Weller et al, 2015). We employed now the same approach in connection with the NPF event at Kohnen (i.e.…”

“…eq. (3) in Weller et al (2015), using T=250 K), resulting in 1.4×10 7 molec cm -3 gaseous H2SO4 necessary for the determined growth rate of 0.6 nm h -1 . Again, this appeared at least an order of magnitude to high compared to respecting values yet published (e.g.…”

“…The size distribution of the sub-µm aerosol at Kohnen was determined by a scanning mobility particle sizer (SMPS, TSI classifier model 3080; Wang and Flagan (1990)). Set-up and respecting data evaluation methods were virtually identical to our installation run at Neumayer Station, already described in detail elsewhere (Weller et al, 2015). Hence we simply highlight here the most relevant 30 points.…”

“…Finally, denuder experiments conducted by Piel et al (2006) Stohl, 1998). As for coastal site Neumayer we already discussed this point 2015), but for continental Antarctica, the persisting surface inversions 10 and katabatic winds pose additional challenges to air mass trajectory analyses. Though a detailed accuracy assessment is beyond the scope this work, we tried to validate the consistency of the used back trajectories by: (i) using the 3D wind fields of the GDAS data as well as the isentropic approximation which could be more reliable for regions with sparse meteorological input data (Harris et al, 2005); (ii) varying the starting height above ground between 10 m and 100 m. The impact of these different initial conditions on our conclusions will be appraised in the Discussion section.…”