Iodine observed in new particle formation events in the Arctic atmosphere during ACCACIA

Allan, J. D.; Williams, P. I.; Nájera, Juan J.; Whitehead, J. D.; Flynn, Michael J.; Taylor, Jonathan; Liu, Dantong; Darbyshire, Eoghan; Carpenter, Lucy J.; Chance, Rosie; Andrews, Stephen; Hackenberg, Sina; McFiggans, G.

doi:10.5194/acp-15-5599-2015

Cited by 122 publications

(143 citation statements)

References 74 publications

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“…A recent analysis by Roscoe et al (2015) found that linear combinations of IO concentrations measured from satellite could reproduce the seasonal patterns of particle number concentrations measured at Halley and Neumayer during spring, with sulfur explaining the summer peak. Allan et al (2015) have recently shown the involvement of iodine in aerosol nucleation in the Arctic region, suggesting that it could be important in aerosol formation in polar regions. It is possible that DMS or iodine compounds are emitted from the sea-ice and Southern Ocean regions and are transported to the AFT with the ascending polar front and contribute directly to the reservoir of precursors that back trajectories suggest may be present.…”

Section: Discussionmentioning

confidence: 99%

Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

et al. 2016

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Abstract. Better characterisation of aerosol processes in pristine, natural environments, such as Antarctica, have recently been shown to lead to the largest reduction in uncertainties in our understanding of radiative forcing. Our understanding of aerosols in the Antarctic region is currently based on measurements that are often limited to boundary layer air masses at spatially sparse coastal and continental research stations, with only a handful of studies in the vast sea-ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the icebreaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN 3 ) concentrations exhibited a fivefold increase moving across the polar front, with mean polar cell concentrations of 1130 cm −3 -higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low-pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air masses quickly from the free troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea-ice boundary layer air masses travelled equatorward into the low-albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei which, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and their transport pathways described here, could help reduce the discrepancy currently present between simulations and observations of cloud and aerosol over the Southern Ocean.

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Section: Discussionmentioning

confidence: 99%

Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

et al. 2016

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“…3 and 4. In the summertime, NPF occurs within the Arctic boundary layer both in our simulations and in observations Allan et al, 2015). At this time of year, the Arctic region has greater production of oxidants such as OH and has greater dimethyl sulfide (DMS) emissions from the oceanic biological activity, such that oxidation of DMS by OH produces sulfur dioxide (SO 2 ) and, ultimately, sulfuric acid, which contributes to particle formation processes in the boundary layer (e.g.…”

Section: Interpreting Processes Controlling the Annual Cycle Of Aerosmentioning

confidence: 99%

Processes controlling the annual cycle of Arctic aerosol number and size distributions

et al. 2016

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Abstract. Measurements at high-Arctic sites (Alert, Nunavut, and Mt. Zeppelin, Svalbard) during the years 2011 to 2013 show a strong and similar annual cycle in aerosol number and size distributions. Each year at both sites, the number of aerosols with diameters larger than 20 nm exhibits a minimum in October and two maxima, one in spring associated with a dominant accumulation mode (particles 100 to 500 nm in diameter) and a second in summer associated with a dominant Aitken mode (particles 20 to 100 nm in diameter). Seasonal-mean aerosol effective diameter from measurements ranges from about 180 in summer to 260 nm in winter. This study interprets these annual cycles with the GEOS-Chem-TOMAS global aerosol microphysics model. Important roles are documented for several processes (new-particle formation, coagulation scavenging in clouds, scavenging by precipitation, and transport) in controlling the annual cycle in Arctic aerosol number and size.Our simulations suggest that coagulation scavenging of interstitial aerosols in clouds by aerosols that have activated to form cloud droplets strongly limits the total number of particles with diameters less than 200 nm throughout the year. We find that the minimum in total particle number in October can be explained by diminishing new-particle formation within the Arctic, limited transport of pollution from lower latitudes, and efficient wet removal. Our simulations indicate that the summertime-dominant Aitken mode is associated with efficient wet removal of accumulation-mode aerosols, which limits the condensation sink for condensable vapours. This in turn promotes new-particle formation and growth. The dominant accumulation mode during spring is associated with build up of transported pollution from outside the Arctic coupled with less-efficient wet-removal processes at colder temperatures. We recommend further attention to the key processes of new-particle formation, interstitial coagulation, and wet removal and their delicate interactions and balance in size-resolved aerosol simulations of the Arctic to reduce uncertainties in estimates of aerosol radiative effects on the Arctic climate.

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“…The responses of grown new particles and clouds to marine biogenic products are much more complex than those derived from DMS (Quinn and Bates, 2011). NPF events induced by iodine species were frequently observed at coastal locations, e.g., most notably at Mace Head on the west coast of Ireland, in presence of enhanced biological emissions during low-tide, ocean upwelling or the sea-ice melting conditions (O'Dowd et al, 20 2002 a,b;Wen et al, 2006;O'Dowd and de Leeuw, 2007;Ehn et al, 2010;Huang et al, 2010;McFiggans, et al, 2010;Allan et al, 2015;Sellegri et al, 2016). Moreover, amines were reported to enhance H2SO4-H2O nucleation and promote the growth of newly formed particles (Ge et al, 2011;Zhang et al, 2012;Yu et al, 2016;Olenius et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

New particle formation in marine atmosphere during seven cruise campaigns

Zhu

Shen

et al. 2018

Preprint

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Abstract. To study the particle number concentration, size distribution and new particle formation (NPF) events in marine atmosphere, we made measurements during six cruise campaigns over the marginal seas of China in 2011-2016 and one 10 campaign from the marginal seas to the Northwest Pacific Ocean (NWPO) in 2014. We observed relatively frequent NPF events in the atmosphere over the marginal seas of China, i.e., 23 out of 126 observational days with the highest occurrence frequency in fall, followed by spring and summer. 22 out of 23 NPF events were analyzed to be associated with the long-range transport of continental pollutants based on 24-hr air mass back trajectories and the pre-existing particle number concentrations largely exceeding the clean marine background, leaving one much weaker NPF event to be likely induced by oceanic precursors 15 alone and supported by multiple independent evidences. Although the long-range transport signal of continental pollutants can be clearly observed in the remote marine atmosphere over the NWPO, NPF events were observed only in 2 days out of 36 days. The nucleation mode particles (<30 nm), however, accounted for as high as 40%13% of the total particle number concentration during the NWPO cruise campaign, implying that there were many undetected NPF events in the sea-level atmosphere or above. 20To better characterize NPF events, we introduced a term, i.e., the net maximum increase in nucleation mode particles number concentration (NMINP) and correlated it with formation rate of new particles (FR). We found a moderately good linear correlation between NMINP and FR at FR 8 cm -3 s -1 , but there was no correlation at FR >8 cm -3 s -1. The possible mechanisms were argued in terms of roles of different vapor precursors. We also found a ceiling existing for the growth of new particles from 10 nm to larger size in most of NPF events. We thereby introduce a term, i.e., the maximum geometric 25 median diameter of new particles (Dpgmax) and correlate it with the growth rate of new particles (GR). A moderately good linear correlation was also obtained between Dpgmax and GR, and only GR larger than 7.9 nm h -1 can lead to new particles growing with Dpgmax beyond 50 nm. Combining simultaneous measurements of the particle number size distributions and cloud condensation nuclei (CCN) at different super saturations (SS), we indeed observed a clear increase in CCN when the Dpg of new particles exceeded 50 nm at SS=0.4%. However, it was not the case for SS=0.2%. Consistent with previous studies in 30 continental atmosphere, our results implied that 50 nm can be used as the threshold for new particles to be activated as CCN in the marine atmosphere. Moreover, the κ decreased from 0.4 to 0.1 during the growth period of new particles, implying that Atmos. Chem. Phys. Discuss., https://doi

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Iodine observed in new particle formation events in the Arctic atmosphere during ACCACIA

Cited by 122 publications

References 74 publications

Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

Processes controlling the annual cycle of Arctic aerosol number and size distributions

New particle formation in marine atmosphere during seven cruise campaigns

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