The application of a multi-wavelength Aethalometer to estimate iron dust and black carbon concentrations in the marine boundary layer of Cape Verde

Abstract. Combustion-derived aerosols in the marine boundary layer have been poorly studied, especially in remote environments such as the open Atlantic Ocean. The tropical Atlantic has the potential to contain a high concentration of aerosols, such as black carbon, due to the African emission plume of biomass and agricultural burning products. Atmospheric particulate matter samples across the tropical Atlantic boundary layer were collected in the summer of 2010 during the southern hemispheric dry season when open fire events were frequent in Africa and South America. The highest black carbon concentrations were detected in the Caribbean Sea and within the African plume, with a regional average of 0.6 μg m−3 for both. The lowest average concentrations were measured off the coast of South America at 0.2 to 0.3 μg m−3. Samples were quantified for black carbon using multiple methods to provide insights into the form and stability of the carbonaceous aerosols (i.e., thermally unstable organic carbon, soot like, and charcoal like). Soot-like aerosols composed up to 45% of the carbonaceous aerosols in the Caribbean Sea to as little as 4% within the African plume. Charcoal-like aerosols composed up to 29% of the carbonaceous aerosols over the oligotrophic Sargasso Sea, suggesting that non-soot-like particles could be present in significant concentrations in remote environments. To better apportion concentrations and forms of black carbon, multiple detection methods should be used, particularly in regions impacted by biomass burning emissions.

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A Multi-Wavelength Mini Lidar for Measurements of Marine Boundary Layer Aerosol and Water Vapor Fields

10.21236/ada626473 ◽

2002 ◽

Author(s):

Shiv K. Sharma ◽

Barry R. Lienert ◽

John N. Porter

Keyword(s):

Boundary Layer ◽

Water Vapor ◽

Marine Boundary Layer ◽

Multi Wavelength

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Atmospheric electric field in the Atlantic marine boundary layer: first results from the SAIL project

10.5194/egusphere-egu2020-18767 ◽

2020 ◽

Author(s):

Susana Barbosa ◽

Mauricio Camilo ◽

Carlos Almeida ◽

José Almeida ◽

Guilherme Amaral ◽

...

Keyword(s):

Boundary Layer ◽

Electric Field ◽

Marine Boundary Layer ◽

Weather Conditions ◽

Cape Verde ◽

The Other ◽

Atmospheric Electric Field ◽

Fair Weather ◽

Near Surface ◽

First Results

The study of the electrical properties of the atmospheric marine boundary layer is important as the effect of natural radioactivity in driving near surface ionisation is significantly reduced over the ocean, and the concentration of aerosols is also typically lower than over continental areas, allowing a clearer examination of space-atmosphere interactions. Furthermore, cloud cover over the ocean is dominated by low-level clouds and most of the atmospheric charge lies near the earth surface, at low altitude cloud tops. The relevance of electric field observations in the marine boundary layer is enhanced by the the fact that the electrical conductivity of the ocean air is clearly linked to global atmospheric pollution and aerosol content. The increase in aerosol pollution since the original observations made in the early 20th century by the survey ship Carnegie is a pressing and timely motivation for modern measurements of the atmospheric electric field in the marine boundary layer. Project SAIL (Space-Atmosphere-Ocean Interactions in the marine boundary Layer) addresses this challenge by means of an unique monitoring campaign on board the ship-rigged sailing ship NRP Sagres during its 2020 circumnavigation expedition. The Portuguese Navy ship NRP Sagres departed from Lisbon on January 5th in a journey around the globe that will take 371 days. Two identical field mill sensors (CS110, Campbell Scientific) are installed on the mizzen mast, one at a height of 22 m, and the other at a height of 5 meters. A visibility sensor (SWS050, Biral) was also set-up on the same mast in order to have measurements of the extinction coefficient of the atmosphere and assess fair-weather conditions. Further observations include gamma radiation measured with a NaI(Tl) scintillator from 475 keV to 3 MeV, cosmic radiation up to 17 MeV, and atmospheric ionisation from a cluster ion counter (Airel). The 1 Hz measurements of the atmospheric electric field and from all the other sensors are linked to the same rigorous temporal reference frame and precise positioning through kinematic GNSS observations. Here the first results of the SAIL project will be presented, focusing on fair-weather electric field over the Atlantic. The observations obtained in the first three sections of the circumnavigation journey, including Lisbon (Portugal) - Tenerife (Spain), from 5 to 10 January, Tenerife - Praia (Cape Verde) from 13 to 19 January, and across the Atlantic from Cape Verde to Rio de Janeiro (Brasil), from January 22nd to February 14th, will be presented and discussed.

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Evidence for renoxification in the tropical marine boundary layer

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-4081-2017 ◽

2017 ◽

Vol 17 (6) ◽

pp. 4081-4092 ◽

Cited By ~ 16

Author(s):

Chris Reed ◽

Mathew J. Evans ◽

Leigh R. Crilley ◽

William J. Bloss ◽

Tomás Sherwen ◽

...

Keyword(s):

Boundary Layer ◽

Organic Nitrogen ◽

Marine Boundary Layer ◽

Model Simulation ◽

Cape Verde ◽

Box Model ◽

Nitrogen Species ◽

Dominant Source ◽

Mixing Ratios ◽

Solar Noon

Abstract. We present 2 years of NOx observations from the Cape Verde Atmospheric Observatory located in the tropical Atlantic boundary layer. We find that NOx mixing ratios peak around solar noon (at 20–30 pptV depending on season), which is counter to box model simulations that show a midday minimum due to OH conversion of NO2 to HNO3. Production of NOx via decomposition of organic nitrogen species and the photolysis of HNO3 appear insufficient to provide the observed noontime maximum. A rapid photolysis of nitrate aerosol to produce HONO and NO2, however, is able to simulate the observed diurnal cycle. This would make it the dominant source of NOx at this remote marine boundary layer site, overturning the previous paradigm according to which the transport of organic nitrogen species, such as PAN, is the dominant source. We show that observed mixing ratios (November–December 2015) of HONO at Cape Verde (∼ 3.5 pptV peak at solar noon) are consistent with this route for NOx production. Reactions between the nitrate radical and halogen hydroxides which have been postulated in the literature appear to improve the box model simulation of NOx. This rapid conversion of aerosol phase nitrate to NOx changes our perspective of the NOx cycling chemistry in the tropical marine boundary layer, suggesting a more chemically complex environment than previously thought.

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Modeling the smoky troposphere of the southeast Atlantic: a comparison to ORACLES airborne observations from September of 2016

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-11491-2020 ◽

2020 ◽

Vol 20 (19) ◽

pp. 11491-11526 ◽

Cited By ~ 2

Author(s):

Yohei Shinozuka ◽

Pablo E. Saide ◽

Gonzalo A. Ferrada ◽

Sharon P. Burton ◽

Richard Ferrare ◽

...

Keyword(s):

Boundary Layer ◽

Optical Properties ◽

Black Carbon ◽

Marine Boundary Layer ◽

Organic Aerosol ◽

Airborne Lidar ◽

Aerosol Mass ◽

Wide Range ◽

Smoke Layer ◽

Mass Concentrations

Abstract. In the southeast Atlantic, well-defined smoke plumes from Africa advect over marine boundary layer cloud decks; both are most extensive around September, when most of the smoke resides in the free troposphere. A framework is put forth for evaluating the performance of a range of global and regional atmospheric composition models against observations made during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) airborne mission in September 2016. A strength of the comparison is a focus on the spatial distribution of a wider range of aerosol composition and optical properties than has been done previously. The sparse airborne observations are aggregated into approximately 2∘ grid boxes and into three vertical layers: 3–6 km, the layer from cloud top to 3 km, and the cloud-topped marine boundary layer. Simulated aerosol extensive properties suggest that the flight-day observations are reasonably representative of the regional monthly average, with systematic deviations of 30 % or less. Evaluation against observations indicates that all models have strengths and weaknesses, and there is no single model that is superior to all the others in all metrics evaluated. Whereas all six models typically place the top of the smoke layer within 0–500 m of the airborne lidar observations, the models tend to place the smoke layer bottom 300–1400 m lower than the observations. A spatial pattern emerges, in which most models underestimate the mean of most smoke quantities (black carbon, extinction, carbon monoxide) on the diagonal corridor between 16∘ S, 6∘ E, and 10∘ S, 0∘ E, in the 3–6 km layer, and overestimate them further south, closer to the coast, where less aerosol is present. Model representations of the above-cloud aerosol optical depth differ more widely. Most models overestimate the organic aerosol mass concentrations relative to those of black carbon, and with less skill, indicating model uncertainties in secondary organic aerosol processes. Regional-mean free-tropospheric model ambient single scattering albedos vary widely, between 0.83 and 0.93 compared with in situ dry measurements centered at 0.86, despite minimal impact of humidification on particulate scattering. The modeled ratios of the particulate extinction to the sum of the black carbon and organic aerosol mass concentrations (a mass extinction efficiency proxy) are typically too low and vary too little spatially, with significant inter-model differences. Most models overestimate the carbonaceous mass within the offshore boundary layer. Overall, the diversity in the model biases suggests that different model processes are responsible. The wide range of model optical properties requires further scrutiny because of their importance for radiative effect estimates.

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Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer?

10.5194/acp-2021-532 ◽

2021 ◽

Author(s):

Leigh Crilley ◽

Louisa Kramer ◽

Francis Pope ◽

Chris Reed ◽

James Lee ◽

...

Keyword(s):

Boundary Layer ◽

Nitrous Acid ◽

Marine Boundary Layer ◽

Ocean Surface ◽

Cape Verde ◽

Formation Mechanisms ◽

Oh Radicals ◽

Surface Source ◽

Global Impacts ◽

Quantitative Understanding

Abstract. Nitrous acid, HONO, is a key net photolytic precursor to OH radicals in the atmospheric boundary later. As OH is the dominant atmospheric oxidant, driving the removal of many primary pollutants and the formation of secondary species, a quantitative understanding of HONO sources is important to predict atmospheric oxidising capacity. While a number of HONO formation mechanisms have been identified, recent work has ascribed significant importance to the dark, ocean-surface mediated conversion of NO2 to HONO in the coastal marine boundary layer. In order to evaluate the role of this mechanism, here we analyse measurements of HONO and related species obtained at two contrasting coastal locations – Cape Verde (Atlantic Ocean), representative of the clean remote tropical marine boundary layer, and Weybourne (United Kingdom), representative of semi-polluted Northern European coastal waters. As expected, higher average concentrations of HONO (70 ppt) were observed in marine air for the more anthropogenically influenced Weybourne location compared to Cape Verde (HONO < 5 ppt). At both sites, the approximately constant HONO/NO2 ratio at night pointed to a low importance for the dark ocean-surface mediated conversion of NO2 into HONO, whereas the midday maximum in the HONO/NO2 ratios indicated significant contributions from photo-enhanced HONO formation mechanisms (or other sources). We obtained an upper limit to the rate coefficient of dark ocean-surface HONO-to-NO2 conversion of CHONO = 0.0011 ppb hr−1 from the Cape Verde observations; this is a factor of 5 lower than the slowest rate reported previously. These results point to significant geographical variation in the predominant HONO formation mechanisms in marine environments and indicate that caution is required when extrapolating the importance of such mechanisms from individual study locations to assess regional and/or global impacts on oxidising capacity. As a significant fraction of atmospheric processing occurs in the marine boundary layer, particularly in the tropics, better constraint of the possible ocean surface source of HONO is important for a quantitative understanding of chemical processing of primary trace gases in the global atmospheric boundary layer and associated impacts upon air pollution and climate.

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A Multi-Wavelength Mini Lidar for Measurements of Marine Boundary Layer Aerosol and Water Vapor Fields

10.21236/ada624964 ◽

2001 ◽

Author(s):

Shiv K. Sharma ◽

Barry R. Lienert ◽

John N. Porter ◽

Antony D. Clarke

Keyword(s):

Boundary Layer ◽

Water Vapor ◽

Marine Boundary Layer ◽

Multi Wavelength

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Corrigendum to "Size-resolved observations of refractory black carbon particles in cloud droplets at a marine boundary layer site" published in Atmos. Chem. Phys., 15, 1367–1383, 2015

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-1487-2015 ◽

2015 ◽

Vol 15 (3) ◽

pp. 1487-1487

Author(s):

J. C. Schroder ◽

S. J. Hanna ◽

R. L. Modini ◽

A. L. Corrigan ◽

S. M. Kreidenweis ◽

...

Keyword(s):

Boundary Layer ◽

Black Carbon ◽

Marine Boundary Layer ◽

Chem Phys ◽

Cloud Droplets ◽

Carbon Particles

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Black carbon in the marine boundary layer over the North Atlantic and seas of the Russian arctic in june-september 2017

Океанология ◽

10.31857/s0030-1574595771-776 ◽

2019 ◽

Vol 59 (5) ◽

pp. 771-776

Author(s):

V. P. Shevchenko ◽

V. M. Kopeikin ◽

A. N. Novigatsky ◽

G. V. Malafeev

Keyword(s):

Boundary Layer ◽

Black Carbon ◽

North Atlantic ◽

Marine Boundary Layer ◽

The Arctic ◽

Air Masses ◽

South Eastern ◽

The North ◽

The North Atlantic ◽

Eastern Baltic

The paper presents the results of a study of the concentrations of black carbon in the marine boundary layer over the Baltic and North Seas, the North Atlantic, the Norwegian, the Barents, the Kara and the Laptev seas from June 30 to September 29, 2017 in the 68th and 69th voyages of research vessel "Akademik Mstislav Keldysh". Black carbon has a significant impact on climate change and the degree of pollution of the Arctic. Black carbon is formed as a result of incomplete combustion of fossil fuels (primarily coal, oil) and biomass or biofuel. It consists of submicron particles and their aggregates and can be transported a great distance from the source. Samples were taken by pumping air for 46 hours through quartz filters Hahnemule at an altitude of 10 m above sea level in a headwind to prevent smoke of the vessel from entering the filters. Subsequently, the black carbon content was determined in the laboratory by the aetalometric method. The backward trajectories of the air mass transfer and the black carbon particles transported by them to the sampling points were calculated using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model at http://www.arl.noaa.gov/ready.html. The conducted studies show low values of black carbon concentrations (50 ng/m3) along the expedition route when air masses came from the background areas of the North Atlantic and the Arctic. High concentrations of black carbon (100200 ng/m3 and higher) are characteristic for areas with active navigation (the South-Eastern Baltic, the North Sea) and near ports (eg Reykjavik), as well as for incoming air masses from the industrialized regions of Europe to South-Eastern Baltic and from areas of oil and gas fields where associated gas is flared (the North, the Norwegian and the Kara seas).

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Size-resolved observations of refractory black carbon particles in cloud droplets at a marine boundary layer site

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-11447-2014 ◽

2014 ◽

Vol 14 (8) ◽

pp. 11447-11491 ◽

Cited By ~ 2

Author(s):

J. C. Schroder ◽

S. J. Hanna ◽

R. L. Modini ◽

A. L. Corrigan ◽

A. M. Macdonald ◽

...

Keyword(s):

Boundary Layer ◽

Black Carbon ◽

Marine Boundary Layer ◽

Back Trajectory ◽

Cloud Droplets ◽

Back Trajectories ◽

Air Masses ◽

Carbon Particles ◽

Back Trajectory Analysis ◽

La Jolla

Abstract. Size resolved observations of aerosol particles (including black carbon particles) and cloud residuals were studied at a marine boundary layer site (251 m a.m.s.l.) in La Jolla, CA during 2012. A counterflow virtual impactor was used to sample cloud residuals while a total inlet was used to sample both cloud residuals and interstitial particles. Two cloud events totaling ten hours of in-cloud sampling were analyzed. Since the CVI only sampled cloud droplets larger than &approx;11 μm, less than 100% of the cloud droplets were sampled during the two cloud events (&approx;38% of the cloud droplets for the first cloud event and &approx;24% of the cloud droplets for the second cloud were sampled). Back trajectories showed that air masses for both cloud events spent at least 96 h over the Pacific Ocean and traveled near, or over populated regions just before sampling. Based on bulk aerosol particle concentrations measured from the total inlet the two air masses sampled were classified as polluted marine air, a classification that was consistent with back trajectory analysis and the mass concentrations of refractory black carbon (rBC) measured from the total inlet. The activated fraction of rBC, estimated from the measurements, ranged from 0.01 to 0.1 for core diameters ranging from 70 to 220 nm. Since the fraction of cloud droplets sampled by the CVI was less than 100%, the measured activated fractions of rBC should be considered as lower limits to the total fraction of rBC activated during the two cloud events. Size distributions of rBC sampled from the residual inlet show that sub-100 nm rBC cores were incorporated into the droplets in both clouds. The coating analysis shows that the rBC cores had average coating thicknesses of 75 nm for core diameters of 70 nm and 29 nm for core diameters of 220 nm. The presence of sub-100 nm rBC cores in the cloud residuals is consistent with kappa-Köhler theory and the measured coating thicknesses of the rBC cores.

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