Abstract
Abstract. In this study we present a qualitative and quantitative assessment of more than 10 yr of aerosol number size distribution data observed in the Arctic environment (Mt. Zeppelin (78°56' N, 11°53' E, 474 m a.s.l.), Ny Ålesund, Svalbard). We provide statistics on both seasonal and diurnal characteristics of the aerosol observations and conclude that the Arctic aerosol number size distribution and related parameters such as integral mass and surface area exhibit a very pronounced seasonal variation. This seasonal variation seems to be controlled by both dominating source as well as meteorological conditions. Three distinctly different periods can be identified during the Arctic year: the haze period characterized by a dominating accumulation mode aerosol (March–May), followed by the sunlit summer period with low abundance of accumulation mode particles but high concentration of small particles which are likely to be recently and locally formed (June–August). The rest of the year is characterized by a comparably low concentration of accumulation mode particles and negligible abundance of ultrafine particles (September–February). A minimum in aerosol mass and number concentration is usually observed during September/October. We further show that the transition between the different regimes is fast, suggesting rapid change in the conditions defining their appearance. A source climatology based on trajectory analysis is provided, and it is shown that there is a strong seasonality of dominating source areas, with Eurasia dominating during the Autumn–Winter period and dominance of North Atlantic air during the summer months. We also show that new-particle formation events are rather common phenomena in the Arctic during summer, and this is the result of photochemical production of nucleating/condensing species in combination with low condensation sink. It is also suggested that wet removal may play a key role in defining the Arctic aerosol year, via the removal of accumulation mode size particles, which in turn have a pivotal role in facilitating the conditions favorable for new-particle formation events. In summary the aerosol Arctic year seems to be at least qualitatively predictable based on the knowledge of seasonality of transport paths and associated source areas, meteorological conditions and removal processes.
Highlights
M low abundance of accumulation mode particles but high con- 1 Introduction centration of small particles which are likely to be recently and locally formed (June–August)
A source climatology based on are characteristic of warming results in, ftohrOe eAxcarecmtaipclnee,nSvanircoeinaemrlnieencrte.onTsheits increased of sea ice trajectory analysis is provided, and it is shown that there is melt and ice loss in general, through which positive feeda strong seasonality of dominating source areas, with Eura- back further impacts the radiative balance via reduced sursia dominating during the Autumn–Winter period and dom- face albedo (Hudson, 2011; Robock, 1983)
In this study we have presented a 10 yr data set of aerosol size distribution measurements collected at the Zeppelin station located in Svalbard
Summary
M low abundance of accumulation mode particles but high con- 1 Introduction centration of small particles which are likely to be recently and locally formed (June–August). Several studalso show that new-particle formation events are rather com- ies have suggested that the ASrcoticliOdceEanamrtahy be seasonally mon phenomena in the Arctic during summer, and this is the ice free in the 30–40 yr (Serreze et al, 2007; Wang and Overland, 2009) The climatic influence of aerosol particles is a result of their ability to both directly scatter and absorb incoming shortwave solar radiation (Charlson et al, 1992) The former is assumed to result in a net cooling of the lower atmosphere and surface, while the latter may cause warming of the atmosphere and subsequently the surface due to increased down welling of long-wave radiation. High sun and dark surfaces will favor shortwave forcing (i.e. during the summer period), whereas bright surfaces and low sun or darkness will favor the longwave radiation forcing (i.e. during the winter period)
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