Arctic aerosol life cycle: linking aerosol size distributions observed between 2000 and 2010 with air mass transport and precipitation at Zeppelin station, Ny-Ålesund, Svalbard

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. <br><br> 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

Measurements of aerosol and CCN properties in the Mackenzie River delta (Canadian Arctic) during spring–summer transition in May 2014

“…Consequently, the Arctic aerosol particle number size distribution and the particle number concentrations show a large seasonal variability (Tunved et al, 2013). Moreover, the sources and sinks for Arctic aerosol particles are subject to the fast changes in the Arctic that currently take place.…”

“…The major part of the Arctic haze consists of particulate organic matter (POM) and sulfate but also contains ammonium, nitrate, mineral dust, black carbon and heavy metals (Quinn et al, 2002). Reported PNSDs show an accumulation mode with N CN constantly increasing during the winter months from October until April from below 50 to above 200 cm −3 (Tunved et al, 2013).…”

“…Additionally, ammonia, also a contributor to NPF, was described to be connected to seabird colonies by Croft et al (2016b) and Wentworth et al (2016) and was discussed to have a farranging influence on the Arctic aerosol. In general, during the Arctic summer locally and freshly produced aerosol particle species are dominant, driven by an increase in both biological activity and photochemistry (Ström et al, 2009) and showing up as a pronounced Aitken mode in PNSDs in summer month, particularly in July and August (Tunved et al, 2013).…”

“…Connected to that, there are recurring yearly cycles of both particle number concentrations (N CN ) and particle number size distributions (PNSDs). Tunved et al (2013) describe these cycles based on measurements taken for the years 2000 to 2010 at Mt. Zeppelin on Svalbard.…”

“…During the transition from spring to summer an increased vertical mixing causes the presence of low-level clouds, and the related wet removal stops the Arctic haze period (Tunved et al, 2013), making the well-aged (Heintzenberg, 1980) Arctic haze particles of the accumulation mode disappear (Engvall et al, 2008;Tunved et al, 2013). Indeed, these precipitation-related scavenging processes, which are effective from late spring throughout the summer, were shown to be among the drivers of the yearly cycle in Arctic PNSDs (Browse et al, 2012;Croft et al, 2016a).…”