Characterization of aerosol optical depth (AOD) anomalies in September and October 2022 over Skukuza in South Africa

Atmospheric chemistry and physics, Journal Year: 2025, Volume and Issue: 25(6), P. 3519 - 3540

Published: March 25, 2025

Abstract. Most major field campaigns, such as the Southern Africa Fire Atmosphere Research Initiative (SAFARI-92 and SAFARI-2000) AErosol, RadiatiOn CLOuds in southern (AEROCLO-sA), have focused on west coast of Africa, leaving east underexplored. To address this, Biomass Burning Aerosol Campaign (BiBAC) was initiated by IRP ARSAIO (International Project – Atmospheric Indian Ocean) during 2022 biomass burning season to study aerosol optical properties over southwestern Ocean (SWIO). This analyzes intensive observation period (IOP) BiBAC at Skukuza Kruger National Park two events: 18–23 September (Event 1) 9–17 October 2). Sun-photometer data, consistent with CALIOP (Cloud-Aerosol Lidar Orthogonal Polarization), revealed a predominance aerosols. Transport analyses show southeastward movement carbon monoxide (CO) aerosols, reaching up 6 km Event 1 10 2. Synoptic conditions, including frontal systems baroclinic waves, drove regional intercontinental pollutant transport, impacting Mozambique Channel surrounding areas. A “river smoke” observed suggests novel synoptic conditions compared previous studies. is first highlight distinct transport mechanisms plumes CO from South America toward SWIO basin, underscoring significance east-coast observations understanding global atmospheric dynamics.

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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Improved simulations of biomass burning aerosol optical properties and lifetimes in the NASA GEOS Model during the ORACLES-I campaign

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(7), P. 4421 - 4449

Published: April 16, 2024

Abstract. In order to improve aerosol representation in the NASA Goddard Earth Observing System (GEOS) model, we evaluated simulations of transport and properties aerosols from southern African biomass burning sources that were observed during first deployment ORACLES (ObseRvations Aerosols above CLouds their intEractionS) field campaign September 2016. An example case study 24 was analyzed detail, which aircraft-based situ remote sensing observations showed presence a multi-layered smoke plume structure with significant vertical variation single scattering albedo (SSA). Our baseline GEOS not able represent SSA or organic aerosol-to-black-carbon ratio (OA : BC). Analyzing simulated age suggests higher-altitude, less absorbing younger (∼4 d), while lower-altitude more older (∼7 d). We hypothesize chemical microphysical loss process exists explain change absorption as ages, apply simple rate model hydrophilic OA simulate this process. also utilized airborne better constrain simulation optical properties, adjusting assumed particle size, hygroscopic growth, absorption. final additional updated optics performance simulating depth (AOD) compared independent ground- space-based retrievals for entire month 2016, including Ozone Monitoring Instrument (OMI) Aerosol Index. terms radiative implications our adjustments, suggested decreased atmospheric warming about 10 % (∼2 W m−2) over southeastern Atlantic region stratocumulus cloud decks simulations. These results age, transport, system models.

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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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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Using modelled relationships and satellite observations to attribute modelled aerosol biases over biomass burning regions

Nature Communications, Journal Year: 2022, Volume and Issue: 13(1)

Published: Oct. 7, 2022

Biomass burning (BB) is a major source of aerosols that remain the most uncertain components global radiative forcing. Current models have great difficulty matching observed aerosol optical depth (AOD) over BB regions. A common solution to address modelled AOD biases scaling emissions. Using relationship from an ensemble and satellite observations, we show bias in modelling results primarily incorrect lifetimes underestimated mass extinction coefficients. In turn, these seem be related precipitation particle sizes. We further boosting emissions correct region causes overestimation outflow Africa by 48%, leading double warming effect compared with when are simultaneously addressed for both aforementioned factors. Such deviations particularly concerning future increasing fires.

Language: Английский

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Aerosol Optical Properties and Types over Southern Africa and Reunion Island Determined from Ground-Based and Satellite Observations over a 13-Year Period (2008–2021)

Remote Sensing, Journal Year: 2023, Volume and Issue: 15(6), P. 1581 - 1581

Published: March 14, 2023

Fires occur seasonally in Southern Africa, from June to November, increasing tropospheric aerosol loading and triggering harmful consequences for the environment human health. This study aims examine 13 years of optical characteristics types over Africa Reunion Island. Using AERONET sun photometers MODIS observations, we found that a high depth Angström exponent are associated with two predominant aerosols (biomass burning/urban industrial mixed type) throughout spring season. According CALIOP major occurrence frequencies above 10% polluted continental/smoke, dust, elevated smoke, whereas clean continental, dusty marine have below 1%. In comparison other seasons, vertical profiles smoke different shapes spring, seasonal shift peak altitude (from 3–4 km), when fire activity is at its maximum. At these altitudes, northern regions presented 32% on average, while lower values were southern or farthest (<10–20% average). The Lagrangian HYSPLIT model back-trajectories demonstrated eastward transport, air masses South America Atlantic Ocean recirculate around sites. mainly derived active biomass burning areas near sites and, lesser extent, remote sources such as America.

Language: Английский

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Long term observations of biomass burning aerosol over Warsaw by means of multiwavelength lidar

Optics Express, Journal Year: 2023, Volume and Issue: 31(20), P. 33150 - 33150

Published: Aug. 15, 2023

High quality lidar measurements of PollyXT operating at the University Warsaw in years 2013-2022 were analyzed to present a comprehensive optical characterization biomass burning aerosols over Warsaw. The directions aerosol inflows by dividing advection cases into four types, according area origin: Western Europe, Eastern Iberian Peninsula, and North America. It was shown that properties smoke vary each these emphasized aging processes are important. found as aerosol's age increases, there is more backscattering less extinction 355 nm relation 532 nm. analysis ratio demonstrated main changes process observed UV spectra.

Language: Английский

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Impact of biomass burning aerosols (BBA) on the tropical African climate in an ocean–atmosphere–aerosol coupled climate model

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(21), P. 12509 - 12535

Published: Nov. 12, 2024

Abstract. The impact of biomass burning aerosols (BBA) emitted in central Africa on the tropical African climate is studied using ocean–atmosphere global model CNRM-CM, including prognostic aerosols. direct BBA forcing, cloud feedbacks (semi-direct effects), effects surface solar radiation, atmospheric dynamics and precipitation are analysed for 1990–2014 period. During June–July–August (JJA) season, CNRM-CM simulations reveal a semi-direct effect exerted low-level clouds with an increase fraction ∼5 %–10 % over large part ocean. positive radiative found to be mainly due sea temperature response (decrease ∼0.5 K) associated heating at 700 hPa, which increases lower-tropospheric stability. Over land, results also indicate low-cloud fraction, especially coastal regions Gabon Angola, potentially enhanced these coupled that integrates (cooling) (SST). In addition SST, highlight oceanic noticeable (about −0.2 −0.4 down ∼80 m depth JJA between coast 10° W. parallel clouds, reductions obtained mid-level Africa, BBA-induced cooling inhibiting convection. terms optical properties, induced about ∼2–3 ocean south Equator. result feedback modulates radiation whole Africa. strongest dimming (∼-30 W m−2), leading reduction continental (by ∼1 2 K), but affected up Brazilian coast. With respect hydrological cycle, show negative western coast, decrease mm d−1. This study highlights persistent (increase liquid water content depth) during September–October–November (SON) period, explained by residual most SON, simulated Gulf Guinea, As JJA, analysis clearly important role slow SON confirms need use modelling platforms climate.

Language: Английский

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