Abstract
[1] We evaluate the impact of transport from midlatitudes on aerosol number concentrations in the accumulation mode (light‐scattering particles (LSP) with diameters >180 nm) in the Arctic during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. We focus on transport from the Asian continent. We find marked contrasts in the number concentration (NLSP), transport efficiency (TEN_LSP, the fraction transported from sources to the Arctic), size distribution, and the chemical composition of aerosols between air parcels from anthropogenic sources in East Asia (Asian AN) and biomass burning sources in Russia and Kazakhstan (Russian BB). Asian AN air had lower NLSP and TEN_LSP (25 cm �3 and 18% in spring and 6.2 cm �3 and 3.0% in summer) than Russian BB air (280 cm �3 and 97% in spring and 36 cm �3 and 7.6% in summer) due to more efficient wet scavenging during transport from East Asia. Russian BB in this spring is the most important source of accumulation‐mode aerosols over the Arctic, and BB emissions are found to be the primary source of aerosols within all the data in spring during ARCTAS. On the other hand, the contribution of Asian AN transport had a negligible effect on the accumulation‐mode aerosol number concentration in the Arctic during ARCTAS. Compared with background air, NLSP was 2.3–4.7 times greater for Russian BB air but 2.4–2.6 times less for Asian AN air in both spring and summer. This result shows that the transport of Asian AN air decreases aerosol number concentrations in the Arctic, despite the large emissions of aerosols in East Asia. The very low aerosol number concentrations in Asian AN air were caused by wet removal during vertical transport in association with warm conveyor belts (WCBs). Therefore, this cleansing effect will be prominent for air transported via WCBs from other midlatitude regions and seasons. The inflow of clean midlatitude air can potentially have an important impact on accumulation‐mode aerosol number concentrations in the Arctic. Citation: Matsui, H., et al. (2011), Accumulation‐mode aerosol number concentrations in the Arctic during the ARCTAS aircraft campaign: Long‐range transport of polluted and clean air from the Asian continent, J. Geophys. Res., 116, D20217, doi:10.1029/2011JD016189.
Highlights
Spring NBCa MBCa RORGb (%) RSO4b (%) APTa,c Russia + AsiaRussia + Asia BB, ANBB BB, ANBBSummer aMedian values are shown for these parameters. bRA denotes the average mass ratio of species A to the total measured submicron mass concentration. cAPT denotes accumulated precipitation along trajectories.this region and season and are generally due to warm conveyor belts (WCBs) [e.g., Stohl, 2001; Eckhardt et al, 2003; Oshima et al, 2004; Harrigan et al, 2011; Sessions et al., 2010]
We evaluate the impacts of transport from the midlatitudes on aerosol number concentrations in the accumulation mode (measured diameters of 180–860 nm) in the Arctic, especially from the Asian continent
We focus on air parcels from Asia because the Aircraft and Satellites (ARCTAS) measurements were made mainly over the Alaskan and Canadian Arctic region, which received air mostly originating from Asia [Fuelberg et al, 2010]
Summary
[2] High concentrations of aerosols occur in the Arctic (Arctic Haze) in winter and spring because of efficient. [Leaitch et al, 1994], over the Alaskan Arctic Ocean during May 1998 [Yum and Hudson, 2001], and during the Arctic Study of Tropospheric Aerosol and Radiation (ASTAR) campaign in March 2000 [Yamanouchi et al, 2005] and in May–June 2004 [Engvall et al, 2008a] They did not fully clarify the impact of different source regions and types (anthropogenic or biomass burning) of aerosols in the MT and UT and did not interpret aerosol pathways and processes during long‐range transport from sources to the Arctic. [5] Aerosol number concentrations were measured extensively during the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) aircraft campaign conducted in and near the Arctic in April and June–July 2008 [Jacob et al, 2010] Using these data, we evaluate the impacts of transport from the midlatitudes on aerosol number concentrations in the accumulation mode (measured diameters of 180–860 nm (section 2)) in the Arctic, especially from the Asian continent.
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