Atmospheric Chemistry and Physics, vol. 13, issue 7 (2013) pp. 3643-3660 Published by Copernicus GmbH
In this study we present a qualitative and quan- titative assessment of more than 10 yr of aerosol number size distribution data observed in the Arctic environment (Mt. Zeppelin (78◦560 N, 11◦530 E, 474ma.s.l.), Ny ˚ Svalbard). We provide statistics on both seasonal and diur- nal 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 peri- ods 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 accumulationmode particles but high con- centration 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 accu- mulation mode particles and negligible abundance of ultra- fine 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 Eura- sia dominating during the Autumn–Winter period and dom- inance of North Atlantic air during the summer months. We also show that new-particle formation events are rather com- mon 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 defin- ing the Arctic aerosol year, via the removal of accumula- tion mode size particles, which in turn have a pivotal role in facilitating the conditions favorable for new-particle for- mation 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.
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