Marine boundary layer aerosol in the eastern North Atlantic: seasonal variations and key controlling processes
The response of marine low cloud systems to changes in aerosol concentrationrepresents one of the largest uncertainties in climate simulations. Majorcontributions to this uncertainty are derived from poor understanding of aerosolunder natural conditions and the perturbation by anthropogenic emission...
| Published in: | Atmospheric Chemistry and Physics |
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| Main Authors: | , , , , , , , , , , , |
| Language: | unknown |
| Published: |
2022
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| Subjects: | |
| Online Access: | http://www.osti.gov/servlets/purl/1485781 https://www.osti.gov/biblio/1485781 https://doi.org/10.5194/acp-18-17615-2018 |
| Summary: | The response of marine low cloud systems to changes in aerosol concentrationrepresents one of the largest uncertainties in climate simulations. Majorcontributions to this uncertainty are derived from poor understanding of aerosolunder natural conditions and the perturbation by anthropogenic emissions. Theeastern North Atlantic (ENA) is a region of persistent but diverse marineboundary layer (MBL) clouds, whose albedo and precipitation are highlysusceptible to perturbations in aerosol properties. In this study, we examineMBL aerosol properties, trace gas mixing ratios, and meteorologicalparameters measured at the Atmospheric Radiation Measurement Climate ResearchFacility's ENA site on Graciosa Island, Azores, Portugal, during a 3-yearperiod from 2015 to 2017. Measurements impacted by local pollution onGraciosa Island and during occasional intense biomass burning and dust eventsare excluded from this study. Submicron aerosol size distribution typicallyconsists of three modes: Aitken (At, diameter <~100 nm),accumulation (Ac, D p within ~100 to ~300 nm), andlarger accumulation (LA, D p > ~ 300 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="54pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="698ff762b5059c7824ca59f7cc9cf5ff"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-17615-2018-ie00002.svg" width="54pt" height="14pt" src="acp-18-17615-2018-ie00002.png"/></svg:svg> nm) modes, with averagenumber concentrations (denoted as N At , N Ac , and N LA below) of 330, 114, and 14 cm -3 , respectively. N At , N Ac , and N LA show contrasting seasonalvariations, suggesting different sources and removal processes. N LA is dominated by sea spray aerosol (SSA) and is higher in winter andlower in summer. This is due to the seasonal variations of SSA production,in-cloud coalescence scavenging, and dilution by entrained free troposphere(FT) air. In comparison, SSA typically contributes a relatively minorfraction to N At (10 %) and N Ac (21 %) on an annual ... |
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