Modeled and observed properties related to the direct aerosol radiative effect of biomass burning aerosol over the southeastern Atlantic

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(1), P. 1 - 46

Published: Jan. 3, 2022

Abstract. Biomass burning smoke is advected over the southeastern Atlantic Ocean between July and October of each year. This plume overlies mixes into a region persistent low marine clouds. Model calculations climate forcing by this vary significantly in both magnitude sign. NASA EVS-2 (Earth Venture Suborbital-2) ORACLES (ObseRvations Aerosols above CLouds their intEractionS) had deployments for field campaigns off west coast Africa 3 consecutive years (September 2016, August 2017, 2018) with goal better characterizing as function monthly evolution measuring parameters necessary to calculate direct aerosol radiative effect. Here, dataset satellite retrievals cloud properties are used test representation underlying layer two regional models (WRF-CAM5 CNRM-ALADIN) global (GEOS UM-UKCA). The focus on comparisons those that primary determinants effect vertical distribution its properties. representativeness observations averages tested campaign, sampled mean light extinction generally found be within 20 % at altitudes. When compared observations, all models, simulated too vertically diffuse has smaller gradients, UM-UKCA), core displaced lower than observations. Plume carbon monoxide, black carbon, organic masses indicate underestimates modeled concentrations, leading, general, mid-visible optical depth. Biases single scatter albedo positive negative across models. Observed gradients not captured but do capture coarse temporal evolution, correctly simulating higher values (2018) (2017) September (2016). Uncertainties measured absorption Ångstrom exponent were large propagate negligible (<4 %) uncertainty integrated solar and, therefore, biases fraction, scene below plume, four thickness clouds is, average, well WRF-CAM5 ALADIN stratocumulus underestimated GEOS model; UM-UKCA simulates high. Overall, study demonstrates utility repeated, semi-random sampling multiple can give insights model how these affect forcing. combined impact (DARE) estimated using first-order approximation subset five comparison grid boxes. A significant finding observed box average yield (warming) boxes, whereas DARE grid-box-averaged ranges from much larger small, values. It shown quantitatively offset other, so improvements reduce only one property (e.g., fraction) would lead even greater DARE. Across fraction depth contribute largest DARE, also making contribution.

Language: Английский

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Challenges and Prospects of Aerosol-Cloud-Precipitation Studies Over Africa

Qeios, Journal Year: 2025, Volume and Issue: 7(1)

Published: Jan. 6, 2025

Africa's distinctive climate and varied terrain present a crucial domain for examining the intricate relationships between aerosol-cloud-precipitation their implications regional climate, water resources, agriculture. Advances in satellite technology, field research, numerical modeling have propelled progress this field. Satellite instruments facilitated understanding of aerosol properties interplay with clouds precipitation, while ground-based airborne measurements from initiatives like Aerosols, Radiation, Clouds southern Africa AEROCLO-sA, Dynamics-Aerosol-Chemistry-Cloud Interactions West DACCIWA provided essential data complementing observations. However, challenges persist, including scarcity, rugged landscapes, uncertainties feedback mechanisms. Machine learning, state-of-the-art sensors advanced high-resolution lidar systems offer promise enhancing observation dynamics. Collaborative research efforts, such as EU–Africa Innovation Cooperation Programs, which engage international partnerships, potential to facilitate knowledge exchange, improve skills, promote sharing.

Language: Английский

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More biomass burning aerosol is being advected westward over the southern tropical Atlantic since 2003

The Science of The Total Environment, Journal Year: 2025, Volume and Issue: 965, P. 178506 - 178506

Published: Jan. 30, 2025

Language: Английский

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A meteorological overview of the ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign over the southeastern Atlantic during 2016–2018: Part 2 – Daily and synoptic characteristics

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(21), P. 14209 - 14241

Published: Nov. 8, 2022

Abstract. Part 1 (Ryoo et al., 2021) provided a climatological overview of the ObsErvation Aerosols above CLouds and their intEractionS (ORACLES) period assessed representativeness deployment years. In part 2, more detailed meteorological analyses support interpretation airborne measurements for aerosol transport its interaction with low clouds over southeastern (SE) Atlantic Ocean during September 2016, August 2017, October 2018 deployments at daily synoptic scale. The key characteristics 2016 are (1) southern African easterly jet (AEJ-S), centered around 600 hPa (∼4 km), which strengthens throughout month in concert warming continental heat low, strongest winds occurring 23 September. These advect both moisture free troposphere. (2) Mid-tropospheric black carbon (BC) is entrained times into boundary layer, (3) convection land dry south about 10∘ S moist north S. mean low-cloud fraction (low CF) well correlated high tropospheric stability (LTS, r=0.44–0.73 flight domain; 0–10∘ E, 5–25∘ S) moderately layer height (BLH, r=0.37–0.52), defined as altitude maximum vertical gradient moisture. For 2017 deployment, primary that AEJ-S lower (∼3 km; ∼700 hPa) further (5–7∘ than only becomes established by 20 August, separate present aloft 500 (∼5.5 km) before that, mid-tropospheric BC–RH coupling after develops, 3 km, CF less closely LTS (r=0.16–0.57) BLH (r=0.11–0.25) (4) reaches 700 Namibian–Kalahari dryland (∼15–25∘ S, ∼18–24∘ E), generating plume subsequently advected AEJ-S. develops hPa, driven Kalahari (∼10–25∘ ∼12–24∘ but it diminishes time moves southward, offshore advection BC water vapor strongly modulated 8–10∘ early October, this decreases mid-latitude frontal systems develop weakens mid-to-late AEJ-S–low-level (LLJ) coastal Namibian region relationship among all months, largely reduced strong LLJ, especially to cloud deck's south, insignificant compared other 2 partially due variability introduced passage disturbance.

Language: Английский

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Seasonal variations in fire conditions are important drivers in the trend of aerosol optical properties over the south-eastern Atlantic

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(13), P. 8767 - 8785

Published: July 7, 2022

Abstract. From June to October, southern Africa produces one-third of the global biomass burning (BB) emissions by widespread fires. BB aerosols are transported westward over south-eastern Atlantic with mid-tropospheric winds, resulting in significant radiative effects. Ascension Island (ASI) is located midway between and South America. 2016 October 2017, a 17-month situ observation campaign on ASI found low single-scattering albedo (SSA) as well high mass absorption cross-section black carbon (MACBC), demonstrating strong absorbing marine boundary layer Atlantic. Here we investigate monthly variations critical optical properties aerosols, i.e. SSA MACBC, during seasons driving factors behind these variations. Both MACBC increase from August decrease September October. The average 0.81 at 529 nm wavelength, highest mean ∼ 0.85 lowest 0.78 August. enhancement (Eabs) derived shows similar trends SSA, whole 1.96 2.07 respectively. As Eabs higher than 1.5 commonly adopted value climate models, this result suggests more model simulations. We find enhanced ratio BC CO (ΔBC/ΔCO, equal BC/ΔCO background concentration considered be 0) correlated providing simple way estimate aerosol characteristics exponential function proposed can approximate BC/ΔCO, when small it capture rapid growth decreases. influenced combustion conditions scavenging. analysis location BB, primary source fuel, water content combined cloud cover precipitation transport areas plume, conclude that likely caused becoming flaming. reduction fuels may responsible for change two factors, one being lower proportion flaming conditions, possibly associated surface wind speed area, other an pathway, leading scavenging, which ultimately results MACBC.

Language: Английский

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An attribution of the low single-scattering albedo of biomass burning aerosol over the southeastern Atlantic

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(8), P. 4775 - 4799

Published: April 24, 2023

Abstract. Aerosol over the remote southeastern Atlantic is some of most sunlight-absorbing aerosol on planet: in situ free-tropospheric single-scattering albedo at 530 nm wavelength (SSA530 nm) ranges from 0.83 to 0.89 within ORACLES (ObseRvations Aerosols above CLouds and their intEractionS) aircraft flights late August–September. Here we seek explain low SSA. The SSA depends strongly black carbon (BC) number fraction, which 0.15 0.4. Low organic (OA)-to-BC mass ratios 8–14 modified combustion efficiency values >0.975 point indirectly dry, flame-efficient primarily grass fuels, with back trajectories ending miombo woodlands Angola. youngest aerosol, aged 4–5 d since emission, occupied top half a 5 km thick plume sampled directly west Angola vertically consistent BC:ΔCO (carbon monoxide) ratio, indicating homogenization source emissions. younger transported more quickly off continent by stronger winds, overlaid older, slower-moving larger mean particle size fraction BC-containing particles. This ongoing gas condensation coagulation smaller non-BC particles upon volumes OA:BC older were smaller, attributed evaporation following fragmentation, instead dilution or thermodynamics. CLARIFY (CLoud–Aerosol–Radiation Interaction Forcing: Year 2017) campaign aerosols that had traveled further reach Ascension Island. reported higher BC fractions, lower ratios, yet absorption coefficients compared this study's. Values one 2017 flight, held midway Island, are intermediate, confirming long-range changes. Overall data continuing oxidation through fragmentation releasing subsequently enter phase, reducing OA mass, rather than support best fit: SSA530nm=0.801+0055⋅(OA:BC) (r=0.84). fires southern Africa emit approximately one-third world's carbon; emitted distinct other regional smoke emissions, composition needs be represented appropriately realistically depict radiative effects.

Language: Английский

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Burning conditions and transportation pathways determine biomass-burning aerosol properties in the Ascension Island marine boundary layer

Atmospheric chemistry and physics, Journal Year: 2025, Volume and Issue: 25(4), P. 2333 - 2363

Published: Feb. 21, 2025

Abstract. African biomass-burning aerosol (BBA) in the southeast Atlantic Ocean (SEA) marine boundary layer (MBL) is an important contributor to Earth's radiation budget, yet its representation remains poorly constrained regional and global climate models. Data from Layered Smoke Interactions with Clouds (LASIC) field campaign on Ascension Island (7.95° S, 14.36° W) provide insight into how burning conditions, fuel type, transport pathways, atmospheric processing affect chemical, microphysical, optical properties of BBA between June September 2017. A total 10 individual plume events characterize seasonal evolution properties. Early-season inefficient fires, determined by low refractory black carbon above-background monoxide mixing ratios (rBC : ΔCO), led enhanced concentrations organic- sulfate-rich aerosols. Mid-season efficient higher rBC ΔCO values, rBC-enriched BBA. mix fires later season resulted conflicting Prolonged (∼ d) through MBL lower free troposphere (FT) facilitated chemical aqueous-phase processing, which a reduction organic mass concentrations. This (OA) (OA rBC) (2–5) compared values (5–15) nearby FT. These cloud oxidation processes yield more light-absorbing explain notably single-scattering albedo at 530 nm (SSA530) (< 0.80) observed MBL. study establishes robust correlation SSA530 OA across FT, underscoring dependency composition.

Language: Английский

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A First Look at the Global Climatology of Low‐Level Clouds in Storm Resolving Models

Journal of Advances in Modeling Earth Systems, Journal Year: 2025, Volume and Issue: 17(3)

Published: March 1, 2025

Abstract The representation of subtropical stratocumulus and trade‐wind cumulus clouds by preliminary versions Integrated Forecasting System (IFS) ICON km‐scale global coupled climate models is explored. These differ profoundly in their strategy to represent subgrid‐scale processes. IFS employs complex parameterizations, including eddy‐diffusivity mass‐flux convection schemes. applies a minimal set paramaterizations, the Smagorinsky‐Lilly closure. Five‐year simulations are performed evaluated for cloud albedo, its variability with environmental parameters vertical structure atmospheric boundary layer eight regions: four corresponding canonical Atlantic Pacific downstream trades. For stratocumulus, both capture albedo's mean, annual cycle, relationship relevant low cloudiness, lower tropospheric stability. They simulate an expected thermodynamic stratocumulus‐topped layer. largely exhibits base inversion height than IFS. We speculate disagreement can be attributed contrasting treatment subgrid mixing top entrainment. In case cumulus, well differentiate amount, character cycles parameter correlations, from upstream stratocumulus. correlations reflect dry wet periods. Both overestimate mean albedo underestimate strength inversion. With additional run, we demonstrate strong sensitivity weaker response mixing.

Language: Английский

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Acceleration of the southern African easterly jet driven by the radiative effect of biomass burning aerosols and its impact on transport during AEROCLO-sA

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(13), P. 8639 - 8658

Published: July 5, 2022

Abstract. The direct and semi-direct radiative effects of biomass burning aerosols (BBAs) are investigated over southern Africa the southeastern Atlantic during Aerosols, Radiation Clouds in (AEROCLO-sA) field campaign September 2017. A reference convection-permitting simulation has been performed using Meso-NH model with an online dust emission scheme, a strongly absorbing BBA tracer emitted daily Global Fire Emissions Database online-computed backward Lagrangian trajectories. captures both aerosol optical depth vertical distribution as observed from airborne spaceborne lidars. occurrence stratocumulus Atlantic, deep convective clouds equatorial large-scale circulation all reproduced by model. If omitted model, we show that (i) smoke plume is too low altitude, (ii) low-cloud cover weak, (iii) activity frequent but not intense enough, (iv) Benguela low-level jet strong, (v) African easterly weak. analysis indicates effect leads to transport higher altitudes, farther southwest stronger diurnal oscillation. altitude can be explained combination three factors: increased upward motion induced jet, self-lofting reduced subsidence associated less western Africa.

Language: Английский

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Use of lidar aerosol extinction and backscatter coefficients to estimate cloud condensation nuclei (CCN) concentrations in the southeast Atlantic

Atmospheric measurement techniques, Journal Year: 2023, Volume and Issue: 16(7), P. 2037 - 2054

Published: April 17, 2023

Abstract. Accurately capturing cloud condensation nuclei (CCN) concentrations is key to understanding the aerosol–cloud interactions that continue feature highest uncertainty amongst numerous climate forcings. In situ CCN observations are sparse, and most non-polarimetric passive remote sensing techniques limited providing column-effective proxies such as total aerosol optical depth (AOD). Lidar measurements, on other hand, resolve profiles of extinction and/or backscatter coefficients better suited for constraining vertically resolved microphysical properties. Here we present relationships between measured by airborne High Spectral Resolution 2 (HSRL-2) in measurements concentrations. The data were obtained during three deployments NASA ObseRvations Aerosols above CLouds their intEractionS (ORACLES) project, which took place over southeast Atlantic (SEA) September 2016, August 2017, September–October 2018. Our analysis spatiotemporally collocated HSRL-2 indicates strong linear both sets. correlation strongest supersaturations (S) greater than 0.25 % dry ambient conditions stratocumulus deck, where relative humidity (RH) less 50 %. We find CCN–HSRL-2 Pearson 0.95–0.97 different parts seasonal burning cycle suggest fundamental similarities biomass (BBA) ORACLES campaign-average values qualitatively similar those from regions types, demonstrating overall representativeness our set. compute CCN–backscatter CCN–extinction regressions can be used vertical across entire above-cloud lidar curtains. These lidar-derived evaluate model performance, illustrate using an example concentration curtain Weather Research Forecasting Model coupled with physics packages Community Atmosphere version 5 (WRF-CAM5). results demonstrate utility deriving expand spatiotemporal coverage or unavailable observations.

Language: Английский

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