Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo

Abstract

Sulfate and organic mass in sea spray explain more than half of the variability in Southern Ocean cloud droplet concentration.

Predicting decadal trends in cloud droplet number concentration using reanalysis and satellite data

“…Several studies have shown that sulfate mass concentration influences CDNC (Boucher and Lohmann, 1995;Lowenthal et 15 al., 2004;McCoy et al, 2017a;McCoy et al, 2015;Storelvmo et al, 2009). Previous studies relating sulfate mass to remotelysensed CDNC were hampered by significant retrieval bias, making the interpretation of their results difficult (McCoy et al, 2017a).…”

“…For the analysis presented in this paper we adopt the technique used in previous studies (Gassó, 2008;Mace and Abernathy, 2016;Yuan et al, 2011;McCoy and Hartmann, 2015;McCoy et al, 2017b;Malavelle et al, 2017) and examine the response of cloud properties to volcanic sulfate sources. We support this analysis by examining the systematic change in 30 anthropogenic sulfur emissions from Asia and North America due to emissions controls , as in previous studies (Bennartz et al, 2011), although our data record extends over a period of enhanced emissions controls in East Asia and thus we anticipate a decrease in CDNC in contrast to Bennartz et al (2011).…”

“…The long-term trends in log 10 CDNC are well-correlated with long-term trends in log 10 SO 4 , with the notable exception of the Australian 25 stratocumulus region ( Figure S3, Figure 5, Figure 6). This is probably because this region is dominated by biogenic sulfur produced by marine organisms (McCoy et al, 2015;Rap et al, 2013;Kloster et al, 2006). The MERRA2 reanalysis uses a climatology to inform it about fluxes of dimethyl-sulfide (Randles et al, 2016) and it has very limited ability to simulate inter-annual variability.…”

Dimethylsulfide (DMS) production in polar oceans may be resilient to ocean acidification

“…Around 3.4 Tg of sulfur is released to the atmosphere between December and February, a flux that represents ~15 % of global annual emissions of DMS (Jarníková and Tortell 2016). Elevated CCN numbers are seen in the most biologically active regions of the Southern Ocean, with a significant contribution from DMS-driven secondary aerosol formation processes (Korhonen 70 et al 2008;McCoy et al 2015). DMS-derived aerosols from this region are estimated to contribute 6 to 10 W m -2 to reflected short wavelength radiation, similar to the influence of anthropogenic aerosols in the polluted Northern Hemisphere (McCoy et al 2015).…”

“…Elevated CCN numbers are seen in the most biologically active regions of the Southern Ocean, with a significant contribution from DMS-driven secondary aerosol formation processes (Korhonen 70 et al 2008;McCoy et al 2015). DMS-derived aerosols from this region are estimated to contribute 6 to 10 W m -2 to reflected short wavelength radiation, similar to the influence of anthropogenic aerosols in the polluted Northern Hemisphere (McCoy et al 2015). Given this important influence of polar DMS emissions on atmospheric processes and climate, it is vital we increase our understanding of the influence of future ocean acidification on DMS 75 production.…”