Improving BC Mixing State and CCN Activity Representation With Machine Learning in the Community Atmosphere Model Version 6 (CAM6)

Journal of Advances in Modeling Earth Systems, Journal Year: 2024, Volume and Issue: 16(1)

Published: Jan. 1, 2024

Abstract Representing mixing state of black carbon (BC) is challenging for global climate models (GCMs). The Community Atmosphere Model version 6 (CAM6) with the four‐mode Modal Aerosol Module (MAM4) represents aerosols as fully internal mixtures uniform composition within each aerosol mode, resulting in high degree BC non‐BC species and large mass ratio coating to ( R , BC‐containing particles). To improve representation, we coupled a machine learning (ML) model index trained on particle‐resolved simulations CAM6 MAM4 (MAM4‐ML). In MAM4‐ML, use partition accumulation mode particles into two new modes, BC‐free particles. We adjust make modeled χ ) match one predicted by ML ). On average, fraction decreases from 100% (MAM4‐default) 48% globally averaged 78% 63% (MAM4‐ML, 19% reduction) agrees well (66%). 52% better observations. hygroscopicity drops 9% leading 20% reduction activation fraction. surface concentration increases most (6.9%) Arctic, burden 4%, globally. Our study highlights application improving key processes GCMs.

Language: Английский

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New SOA Treatments Within the Energy Exascale Earth System Model (E3SM): Strong Production and Sinks Govern Atmospheric SOA Distributions and Radiative Forcing

Journal of Advances in Modeling Earth Systems, Journal Year: 2020, Volume and Issue: 12(12)

Published: Nov. 17, 2020

Abstract Secondary organic aerosols (SOA) are large contributors to fine particle mass loading and number concentration interact with clouds radiation. Several processes affect the formation, chemical transformation, removal of SOA in atmosphere. For computational efficiency, global models use simplified treatments, which often do not capture dynamics formation. Here we test more complex treatments within Energy Exascale Earth System Model (E3SM) investigate how simulated spatial distributions respond some important but uncertain affecting removal, lifetime. We evaluate model predictions a suite surface, aircraft, satellite observations that span globe full troposphere. Simulations indicate both strong production (achieved here by multigenerational aging precursors includes moderate functionalization) sink (especially middle upper troposphere, achieved adding particle‐phase photolysis) needed reproduce vertical distribution aerosol (OA) measured during several aircraft field campaigns; without this sink, tropospheric OA is too large. Our results show variations chemistry formulations change wet lifetime factor 3 due changes horizontal SOA. In all tested here, an efficient is, photolysis, was measurements at high altitudes. Globally, rates photolysis equal decreases lifetimes from 10 ~3 days. A recent review multiple studies found no increase net formation over downwind biomass burning regions, so also alternative, empirical treatment increases primary (POA) emissions near source region converts POA time scale 1 day. Although performs surprisingly well simulating loadings it overestimates troposphere compared measurements, likely convective transport altitudes where weak. The default improved formulation (multigenerational fragmentation much better than these regions. Differences greatly direct radiative effect, ranges −0.65 (moderate −2 W m photolysis). Notably, most predict similar indirect forcing calculated as difference cloud between present‐day preindustrial simulations.

Language: Английский

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Interactions of peroxy radicals from monoterpene and isoprene oxidation simulated in the radical volatility basis set

Environmental Science Atmospheres, Journal Year: 2024, Volume and Issue: 4(7), P. 740 - 753

Published: Jan. 1, 2024

Isoprene affects new particle formation rates in environments and experiments also containing monoterpenes.

Language: Английский

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New particle formation dynamics in the central Andes: contrasting urban and mountaintop environments

Aerosol Research, Journal Year: 2025, Volume and Issue: 3(1), P. 15 - 44

Published: Jan. 14, 2025

Abstract. In this study, we investigate atmospheric new particle formation (NPF) across 65 d in the Bolivian central Andes at two locations: mountaintop Chacaltaya station (CHC, 5.2 km above sea level) and an urban site El Alto–La Paz (EAC), 19 apart 1.1 lower altitude. We classified days into four categories based on intensity of NPF, determined by daily maximum concentration 4–7 nm particles: (1) high both sites, (2) medium both, (3) EAC but low CHC, (4) both. These were then named after their emergent most prominent characteristics: Intense-NPF, Polluted, Volcanic, Cloudy. This classification was premised assumption that similar NPF intensities imply processes. Our findings show significant differences terms size volume, sulfuric acid concentration, aerosol compositions, pollution levels, meteorological conditions, air mass origins. Specifically, intense events increased Aitken mode concentrations (14–100 nm) significantly 28 % when masses passed over Altiplano. At larger (40–100 from × 103 cm−3 (background) to 6.2 cm−3, is very likely linked ongoing process. High levels emissions 24 found interrupt growth CHC diminish nucleation EAC. Meanwhile, 14 days, sulfate large volumes observed, correlating with influences originating actively degassing Sabancaya volcano a depletion positive 2–4 ions not During these reduced observed Lastly, 34 overcast conditions associated rates lowlands east stations. all cases, event initiation (∼ 09:00 LT) generally occurred about half hour earlier than modulated solar cycle. dawn representative regional residual layer minimal local surface influence due barren landscape. As day progresses, upslope winds bring affected altitudes, which may include anthropogenic or biogenic sources. develops gradually, eventually creating right for start. EAC, start rapid boundary layer, favored entrainment above. The study highlights role modifying particles underscores varying impacts versus mountain top environments processes Andean region.

Language: Английский

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Seasonal investigation of ultrafine-particle organic composition in an eastern Amazonian rainforest

Atmospheric chemistry and physics, Journal Year: 2025, Volume and Issue: 25(2), P. 959 - 977

Published: Jan. 27, 2025

Abstract. Reports on the composition of ultrafine particles (<100 nm in diameter) Amazon are scarce, due part to fact that new-particle formation has rarely been observed near ground level. Ultrafine surface have nevertheless observed, leaving open questions regarding sources and chemistry their growth, particularly as these vary across seasons. Here, we present measurements collected Tapajós National Forest (2.857° S, 54.959° W) during three different seasonal periods: 10–30 September 2016 (SEP), 18 November–23 December (DEC), 22 May–21 June 2017 (JUN). Size-selected (5–70 nm) were daily (for h each day) using an offline sampler. Samples time periods compiled analyzed liquid chromatography coupled with Orbitrap high-resolution mass spectrometry. Our findings suggest a sustained influence isoprene organosulfate from periods. We chemical evidence indicates biological-spore fragmentation impacted ultrafine-particle late wet season (JUN), while markers for biomass burning secondary peaked dry (SEP DEC). Higher oxidation states degrees unsaturation organics DEC), suggesting greater extents aerosol aging. Finally, applying volatility parameterization compounds suggests organic sulfur species likely key drivers growth region low compared other species.

Language: Английский

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