Significance of the organic aerosol driven climate feedback in the boreal area

Nature Communications, Journal Year: 2021, Volume and Issue: 12(1)

Published: Sept. 24, 2021

Abstract Aerosol particles cool the climate by scattering solar radiation and acting as cloud condensation nuclei. Higher temperatures resulting from increased greenhouse gas levels have been suggested to lead biogenic secondary organic aerosol nuclei concentrations creating a negative feedback mechanism. Here, we present direct observations on this mechanism utilizing collocated long term chemical composition measurements remote sensing properties. Summer time loadings showed clear increase with temperature, simultaneous in concentration boreal forest environment. Remote revealed change properties an reflectivity concert increasing area. The results provide observational evidence significance of

Language: Английский

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Sea spray aerosol organic enrichment, water uptake and surface tension effects

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(13), P. 7955 - 7977

Published: July 9, 2020

Abstract. The aerosol-driven radiative effects on marine low-level cloud represent a large uncertainty in climate simulations, particular over the Southern Ocean, which is also an important region for sea spray aerosol production. Observations of organic enrichment and resulting impact water uptake remote Hemisphere are scarce, therefore under-represented existing parameterisations. Surface Ocean Aerosol Production (SOAP) voyage was 23 d sampled three phytoplankton blooms highly productive Chatham Rise, east New Zealand. In this study we examined organics to nascent modifications using situ chamber measurements seawater samples taken during SOAP voyage. Primary contributed up % mass particles with diameter less than approximately 1 µm 79 particle volume 50 nm spray. composition submicron fraction consistent throughout largely composed polysaccharide-like component, characterised by very low alkane-to-hydroxyl-concentration ratios 0.1–0.2. compared output from chlorophyll-a-based parameterisation suggested Gantt et al. (2011) OCEANFILMS (Organic Compounds Ecosystems Aerosols: Natural Films Interfaces via Langmuir Molecular Surfactants) models. improved representation predicted chlorophyll a, when co-adsorption polysaccharides included; however, model still under-predicted proportion average 33 %. Nascent hygroscopic growth factors measured at 90 relative humidity averaged 1.93±0.08 did not decrease increasing fractions. observed hygroscopicity greater expected assumption full solubility, particularly most bloom (B1), fractions were 0.4. behaviour that other can be partially attributed presence salt hydrates, lowers low. inclusion surface tension only marginally modelled hygroscopicity, significant discrepancy between high remained. findings highlight influence biologically sourced composition; these data improve capacity parameterise uptake.

Language: Английский

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Significant underestimation of radiative forcing by aerosol–cloud interactions derived from satellite-based methods

Nature Communications, Journal Year: 2021, Volume and Issue: 12(1)

Published: June 15, 2021

Satellite-based estimates of radiative forcing by aerosol-cloud interactions (RFaci) are consistently smaller than those from global models, hampering accurate projections future climate change. Here we show that the discrepancy can be substantially reduced correcting sampling biases induced inherent limitations satellite measurements, which tend to artificially discard clouds with high cloud fraction. Those missed exert a stronger cooling effect, and more sensitive aerosol perturbations. By accounting for biases, magnitude RFaci (from -0.38 -0.59 W m-2) increases 55 % globally (133 over land 33 ocean). Notably, further -1.09 m-2 when switching total optical depth (AOD) fine-mode AOD is better proxy CCN AOD. In contrast previous weak satellite-based RFaci, improved one (especially land), resolving major difference models.

Language: Английский

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Deconvolution of boundary layer depth and aerosol constraints on cloud water path in subtropical stratocumulus decks

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(6), P. 3609 - 3621

Published: March 26, 2020

Abstract. The liquid water path (LWP) adjustment due to aerosol–cloud interactions in marine stratocumulus remains a considerable source of uncertainty for climate sensitivity estimates. An unequivocal attribution LWP adjustments changes aerosol concentration from climatology difficult the covariance between meteorological conditions alongside concentrations. We utilise susceptibility framework quantify potential change with boundary layer (BL) depth subtropical stratocumulus. show that susceptibility, i.e. relative scaled by cloud droplet number concentration, BLs triples magnitude −0.1 −0.31 as BL deepens 300 1200 m and deeper. further find deep be underrepresented pollution tracks, process modelling, situ studies Susceptibility estimates based on these approaches are skewed towards shallow moderate susceptibility. Therefore, extrapolating entire may underestimate true within thus overestimate effective radiative forcing this region. Meanwhile, remain poorly constrained. While found consistent modelling studies, they track

Language: Английский

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Measurement report: Cloud processes and the transport of biological emissions affect southern ocean particle and cloud condensation nuclei concentrations

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(5), P. 3427 - 3446

Published: March 5, 2021

Abstract. Long-range transport of biogenic emissions from the coast Antarctica, precipitation scavenging, and cloud processing are main processes that influence observed variability in Southern Ocean (SO) marine boundary layer (MBL) condensation nuclei (CN) (CCN) concentrations during austral summer. Airborne particle measurements on HIAPER GV north–south transects between Hobart, Tasmania, 62∘ S Clouds, Radiation Aerosol Transport Experimental Study (SOCRATES) were separated into four regimes comprising combinations high low CCN CN. In 5 d HYSPLIT back trajectories, air parcels with elevated almost always shown to have crossed Antarctic coast, a location phytoplankton relative rest SO region south Australia. The presence was also consistent fractions over their trajectory, suggesting there substantial growth biogenically formed particles through processing. Cases fraction, due cumulus clouds, had CN concentrations, previously reported new formation outflow regions. Measurements associated previous 1.5 trajectory indicating effectively scavenged by precipitation. A coarse-mode fitting algorithm used determine primary aerosol (PMA) contribution, which accounted for <20 % (at 0.3 supersaturation) droplet number concentrations. Vertical profiles large (Dp>0.07 µm) indicated occurs more frequently above MBL; however, recently typically MBL, volatile compound oxidation products. R/V Investigator as part second Aerosols, Precipitation, atmospheric Composition Over southeRn (CAPRICORN-2) campaign conducted same period SOCRATES study. near Australia, likely continental coastal emissions. source south, sources midlatitudes, enhanced sink cyclonic circulation Ferrel polar cells (around 60∘ S) create opposing latitudinal gradients concentration an minimum 55 S. airborne not influenced Australian but still show evidence S, addition, gradient composition, Tasmanian coasts, is apparent hygroscopicity derived spectra size distribution. hygroscopic north, greater fraction sea salt PMA, less sulfate organic originating Antarctica.

Language: Английский

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