Features in air ions measured by an air ion spectrometer (AIS) at Dome C

Abstract

for measuring the number size distribution of air ions. In this work, we present results obtained from this air ion data set together with aerosol particle and meteorological data. The main processes that modify the number size distribution of air ions during the measurement period at this high-altitude site included new particle formation (NPF, observed on 85 days), wind-induced ion formation (observed on 36 days), and ion production and loss associated with cloud/fog formation (observed on 2 days). For the subset of days when none of these processes seemed to operate, the concentrations of cluster ions (0.9-1.9 nm) exhibited a clear seasonality, with high concentrations in the warm months and low concentrations in the cold. Compared to event-free days, days with NPF were observed with higher cluster ion concentrations. A number of NPF events were observed with restricted growth below 10 nm, which were termed as suppressed NPF. There was another distinct feature, namely a simultaneous presence of two or three separate NPF and subsequent growth events, which were named as multi-mode NPF events. Growth rates (GRs) were determined using two methods: the appearance time method and the mode fitting method. The former method seemed to have advantages in characterizing NPF events with a fast GR, whereas the latter method is more suitable when the GR was slow. The formation rate of 2 nm positive ions (J + 2 ) was calculated for all the NPF events for which a GR in the 2-3 nm size range could be determined. On average, J + 2 was about 0.014 cm −3 s −1 . The ion production in relation to cloud/fog formation in the size range of 8-42 nm seemed to be a unique feature at Dome C, which has not been reported elsewhere. These ions may, however, either be multiply charged particles but detected as singly charged in the AIS, or be produced inside the instrument, due to the breakage of cloud condensation nuclei (CCN), possibly related to the instrumental behaviour under the extremely cold condition. For the wind-induced ion formation, our observations suggest that the ions originated more likely from atmospheric nucleation of vapours released from the snow than from mechanical charging of shattered snow flakes and ice crystals.

Low‐Volatility Vapors and New Particle Formation Over the Southern Ocean During the Antarctic Circumnavigation Expedition

“…The ion size distribution shows some peculiar bands between 2 and 4 nm, these are probably wind generated ions as similar features have been observed at other snow-covered sites at high wind speeds (X. Chen et al, 2017;Manninen et al, 2010), but it is not clear if they were involved in the NPF process. The effect of wind is shown in Figure S9 in Supporting Information S1, which reports both the negative and positive ion size distribution together with wind speed, relative wind direction and distance to land.…”

“…It is evident that these ion bands are present only for wind speeds larger than about 1 10 m s E in close proximity to land, suggesting that blowing snow may be involved as reported by X. Chen et al (2017).…”

Towards understanding the characteristics of new particle formation in the Eastern Mediterranean

“…Owing to the complex nature and nonlinearity of atmospheric processes, studies on NPF in the literature include atmospheric observations (e.g., Kulmala et al, 2013;Ehn et al, 2014;Bianchi et al, 2016;Yao et al, 2018;Williamson et al, 2019;Baccarini et al, 2020;Dall'Osto et al, 2018), chamber experiments (e.g., Sipilä et al, 2010;Tröstl et al, 2016;Lehtipalo et al, 2016;Kirkby et al, 2011), and theoretical computational studies (e.g., Kurtén et al, 2008;Riipinen et al, 2011;Olenius and Riipinen, 2017). The collective scientific outcome from these studies is essential to understand the mechanisms and characteristics of NPF (Kerminen et al, 2018;Lee et al, 2019;Chu et al, 2019) and how it affects the global climate (e.g., Spracklen et al, 2006;Gordon et al, 2017).…”

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

“…Thus dry deposition, but to an only minor extent wet deposition (partly associated with clear sky precipitation), would be decisive. Consequently future research activities should also envisage assessing dry deposition velocities at this site, e.g., by gradient and/or eddy correlation studies (Grönlund et al, 2002;Contini et al, 2010). On the other hand, retrieving meaningful historic aerosol concentrations from ice core archives also needs a thorough consideration of snow accumulation since snow accumulation co-determines trace compound concentrations in firn and ice (Fischer et al, 1998), which is evidently governed by the infrequent impact of low-pressure systems (Birnbaum et al, 2006;Schlosser et al, 2010;Welker et al, 2014;Kurita et al, 2016).…”