![Scanning electron microscope image of BC aggregates in young smoke from the Madikwe Game Reserve fire, South Africa, on 20 August 2000; (b) transmission electron microscope (TEM) image of chain-like BC aggregates in flaming smoke from the dambo fire near Kaoma, Zambia, on 5 September 2000; (c) TEM image of a compact BC aggregate in regional haze near Skukuza, South Africa, on 22 August 2000 [Li et al., 2003]. (Reproduced with permission of the American Geophysical Union).](https://www.researchgate.net/profile/S-Doherty/publication/260000142/figure/fig18/AS:268044970754097@1440918309889/Scanning-electron-microscope-image-of-BC-aggregates-in-young-smoke-from-the-Madikwe-Game_Q320.jpg)
![Mass and number size distributions of BC particles observed in three fresh urban (red) and two fresh biomass burning (black) plumes as identified in the legend. The measurements are made on board an aircraft using an in situ, single-particle detection instrument (SP2). The variable coatings on the BC particles is not shown. The observed (a) mass and (b) number amounts are plotted as symbols versus volume equivalent diameter based on assuming a spherical particle shape. The mass distributions are normalized to the same peak value. The observations are fit by a lognormal function between 90 and 600 nm (solid lines). The number distribution fits are those consistent with the fit to the respective mass distribution and are scaled to represent the same BC mass. From Schwarz et al. [2008b].](https://www.researchgate.net/profile/S-Doherty/publication/260000142/figure/fig29/AS:268055200661505@1440920748367/Mass-and-number-size-distributions-of-BC-particles-observed-in-three-fresh-urban-red_Q320.jpg)
![Critical supersaturation required to activate particles of varying size and BC content into cloud condensation nuclei. Higher supersaturation values mean that particles are less likely to become cloud droplets. Results are from a particle-resolved model that simulates coagulation and condensation in ambient air onto individual particles. The two branches show aged particles from diesel exhaust (70% BC) and gasoline exhaust (20% BC), assuming that Köhler theory describes activation. Particle diameter has the greatest effect on activation, with BC content inhibiting activation to a lesser extent. Figure is based on simulations [Deville et al., 2011] of particle-resolved model [Riemer et al., 2009].](https://www.researchgate.net/profile/S-Doherty/publication/260000142/figure/fig38/AS:268058887454720@1440921627095/Critical-supersaturation-required-to-activate-particles-of-varying-size-and-BC-content_Q320.jpg)
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Bounding the role of black carbon in the climate system: A Scientific assessment
Abstract and Figures
Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr(-1) in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m(-2) with 90% uncertainty bounds of (+0.08, +1.27) W m(-2). Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m(-2). Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m(-2) with 90% uncertainty bounds of +0.17 to +2.1 W m(-2). Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m(-2), is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (-0.50 to +1.08) W m(-2) during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (-0.06 W m(-2) with 90% uncertainty bounds of -1.45 to +1.29 W m(-2)). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.
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... Black carbon (BC) is a type of carbonaceous aerosol that is formed mainly in flames, is directly emitted to the atmosphere, and strongly absorbs visible light [1][2][3]. It is considered to be responsible for up to 90% of the total aerosol absorption [4,5], even though its mass fraction usually represents from 5 to 15% of the total mass of particulate matter (PM) in urban areas [6][7][8][9]. ...
... It is considered to be responsible for up to 90% of the total aerosol absorption [4,5], even though its mass fraction usually represents from 5 to 15% of the total mass of particulate matter (PM) in urban areas [6][7][8][9]. BC is produced by the incomplete combustion of fossil fuels, biofuels, and biomass [3,[10][11][12], and exists as an aggregate of small carbon spheres formed in flames that rapidly coagulate [1,3]. Due to the high capacity to absorb solar radiation and warming the atmosphere, BC plays an important role in climate change by exerting ...
... It is considered to be responsible for up to 90% of the total aerosol absorption [4,5], even though its mass fraction usually represents from 5 to 15% of the total mass of particulate matter (PM) in urban areas [6][7][8][9]. BC is produced by the incomplete combustion of fossil fuels, biofuels, and biomass [3,[10][11][12], and exists as an aggregate of small carbon spheres formed in flames that rapidly coagulate [1,3]. Due to the high capacity to absorb solar radiation and warming the atmosphere, BC plays an important role in climate change by exerting ...
In this study, the temporal variations of black carbon (BC) were analyzed from November 2019 to September 2021, in Tacna, Peru. Ground measurements obtained with a photoacoustic extinctiometer (PAX BC) and NASA’s MERRA-2 reanalysis data (MERRA-2 BC) were used. The seasonal concentrations of PAX BC (mean ± standard deviation) were as follows: 0.70 ± 0.35, 0.73 ± 0.46, 0.70 ± 0.39, and 0.85 ± 0.46 µg m−3, for spring, summer, autumn, and winter, respectively; while MERRA-2 BC values were 0.12 ± 0.11, 0.06 ± 0.02, 0.06 ± 0.02, and 0.11 ± 0.06 µg m−3, for the same seasons. We found a large discrepancy between these two techniques, as the PAX BC measurements were an order of magnitude higher than the MERRA-2 BC values. In addition, MERRA-2 did not record urban pollution events and did not present the BC weekend effect. The most frequent wind direction (81%) was from the southwest and the sources of greatest contamination were located to the northeast and southeast. The Mann–Kendall test confirmed a downward trend in PAX BC one week (37%) and two weeks (30%) after the start of the COVID-19 lockdown, and no trend in MERRA-2 BC. These results suggest that MERRA-2 underestimates the BC emissions from local sources
... [4][5][6][7][8] Predominantly produced by combustion, soot and black carbon were found to be the second major cause for global warming via direct solar absorption. 9 Particle emissions from on-and off-road vehicles and equipment can be controlled with diesel 10,11 or gasoline particulate lter 12 technologies. However, there are currently no aer treatment systems for controlling particulate emissions from medium and large ship engines. ...
This study evaluates the beneficial effects of discharging nanosecond pulse transient plasma (NPTP) in a coaxial electrostatic precipitator for capturing nanoscale soot particles (∼50 nm) produced by an ethylene flame. Here, the nanoscale soot particles are collected using two different reactor geometries: a 3′′ diameter reactor with a mean flow velocity of 1.2 m s⁻¹ and a 1.5′′ diameter reactor with a mean flow velocity 1.5 m s⁻¹, corresponding to volumetric flow rates of 11.5 CFM and 3.6 CFM, respectively. The nanosecond high voltage pulses (+20 kV, 20 ns, 800 Hz) are applied in conjunction with DC bias voltages. While nearly 100% collection efficiency can be achieved without NPTP at sufficiently high DC voltages (|VDC| > 14 kV), this drops below 50% for lower DC voltages (|VDC| < 10 kV). With NPTP, we observe substantially enhanced remediation (up to 23×) at lower DC voltages (|VDC| < 10 kV) due to the enhanced ion density produced by the plasma. For DC-only electrostatic precipitation, the charging of soot particles takes place via a DC corona, whose ion density is several orders of magnitude lower than that of the NPTP, which produces a streamer discharge due to the fast rise times of the nanosecond pulses (i.e., dV/dt ∼ 10¹² V s⁻¹). High speed imaging of the plasma emission profile indicates that ion densities 10⁶ times higher are achieved with the nanosecond pulsed plasma, as compared to that of the DC corona. At lower DC voltages (i.e., |VDC| < 10 kV), the charging of soot particles is a key factor limiting the DC-only remediation efficiencies, and NPTP provides a way to mitigate this limitation.
... As a result, the simulated average atmospheric age of EC was ∼ 40 h during the regional transport, which was much higher than the "experimental" aging timescale to achieve complete morphology modification and absorption enhancement of BC in Beijing (4.6 h) and Houston, Texas, USA (18 h; Peng et al., 2016). It could be speculated that the aged EC or POA particles are coated continuously by the newly formed fresh SNA particles along the transport route, which could further enhance the light absorption of particles (Bond et al., 2013). Using transmission electron microscopy (TEM), observed abundant spherical primary OM particles coated with secondary aerosols in the YRD during the regional transport, which is consistent with our findings. ...
Atmospheric age reflects how long particles have been suspended in the atmosphere, which is closely associated with the evolution of air pollutants. Severe regional haze events occur frequently in China, influencing air quality, human health, and regional climate. Previous studies have explored the characteristics of mass concentrations and compositions of fine particulate matter (PM2.5) during haze events, but the evolution of atmospheric age remains unclear. In this study, the age-resolved University of California, Davis/California Institute of Technology (UCD/CIT) model was developed and applied to simulate the concentration and age distribution of PM2.5 during a severe regional haze episode in eastern China. The results indicated that PM2.5 concentrations in the North China Plain (NCP) gradually accumulated due to stagnant weather conditions during the beginning stage of the haze event. Accordingly, the atmospheric age of elemental carbon (EC), primary organic aerosol (POA), sulfate (SO42-), and secondary organic aerosol (SOA) gradually increased. The subsequent PM2.5 concentration growth was driven by the local chemical formation of nitrate (NO3-) under high relative humidity. The newly formed NO3- particles led to a decrease in the mean atmospheric age of NO3- particles. During the regional transport stage, aged particles from the NCP moved to the downwind Yangtze River Delta (YRD) region, leading to a sharp increase in PM2.5 concentrations and the average age of EC, POA, SO42-, and SOA in YRD. In contrast, the average age of NO3- and ammonium remained unchanged or even slightly decreased due to continuous local formation in the YRD region. Different evolution of the atmospheric age among these components provides a unique perspective on the formation of PM2.5 components during the regional haze event. The information can also be used for designing effective control strategies for different components of PM2.5.
This study assesses the physical and optical properties and estimated the radiative forcing of aerosol at Agra over the Indo-Gangetic Basin (IGB) during July 2016–December 2019 using black carbon (BC) mass concentration (AE-33 aethalometer), data sets from satellite and model simulations. The optical properties of aerosol and radiative forcing have been measured by the Optical and Physical Properties of Aerosols and Clouds (OPAC) and Santa Barbara Discrete Ordinate Radiative Transfer Atmospheric Radiative Transfer (SBDART) model. The high BC mass concentration has been observed in November and lowest in August. An adverse meteorological condition due to a combination of temperature and low wind speed results in poor dispersion in the wintertime is a common factor for high concentration level pollutants over Agra. The diurnal and temporal cycle of BC mass concentration exhibits a high concentration at nighttime due to the lower atmospheric boundary layer. The seasonal variation of absorption coefficient (βabs) and Absorption Angstrom Exponent (AAE) is found to be higher during post-monsoon and lowest in monsoon season. This suggests that black carbon concentration over Agra is mainly generated from crop burning, waste burning, automobile exhaust and long-range transport from Punjab and Haryana as the present site is downwind. OPAC-derived aerosol optical depth (AOD), single-scattering albedo (SSA), Angstrom Exponent (AE) and asymmetry parameter (AsyP) were estimated to be 0.57 ± 0.07, 0.78 ± 0.16, 0.99 ± 0.21 and 0.81 ± 0.15, respectively. AOD and AE from the OPAC and the moderate resolution imaging spectroradiometer (MODIS) have shown the consistent relationship. The mean radiative forcing is 18.3 ± 2.1 W m−2 at the top of the atmosphere while, at the surface, net radiative forcing is −42.4 ± 7.2 and 59.1 ± 6.5 W m−2 at the atmosphere during the study period. Vertical profiles were estimated using the observations from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite and the change in heating rate from the SBDART model over Agra.
Wildfire emission inventories are usually applied with biome‐scale emission factors for atmospheric modeling. However, emission factors measured for different plant species vary substantially within the same biome. We apply the species‐specific emission factors and refine the Fire Emission Inventory‐northern Eurasia (FEI‐NE), and derive the wildfire black carbon emission inventory in northern Eurasia from 2002 to 2015. Our new inventory produces 61% more black carbon emissions than current estimates based on Global Fire Emission Database (GFED) and 33% less than FEI‐NE. Model simulations with different inventories are compared with ground‐based and satellite retrievals of aerosol absorption optical depth (AAOD). Compared with the Ozone Monitoring Instrument, the normalized root mean square deviation of AAOD over northern Eurasia is reduced from 1.0 under FEI‐NE to 0.95 through application of the new inventory. This study reveals the importance of applying sub‐biome‐scale emission factors for wildfire inventories development and revisiting emissions uncertainty in atmospheric modeling.
Soot particles play an important role in warming the atmosphere, but their optical absorption is highly uncertain due to their variable morphology and mixing states. Compared to short‐range transport, soot particles during long‐range transport normally undergo complicated aging processes. Here, we investigated the changes in microphysical properties and mixing states of soot particles during their long‐range transport in Eastern China. The dominant mixing state of soot particles transformed from partly‐coated at 60% by number to embedded status at 67% when they were transported to a downwind region 1000 km away under cold fronts. The fractal dimension (D f ) increased from 1.79 ± 0.05 for partly‐coated soot and 1.86 ± 0.07 for embedded soot to 1.83 ± 0.06 and 1.93 ± 0.05 following their transportation, respectively. Our study shows that aging processes of soot particles with chain‐like morphology caused their structural collapse. Moreover, we found that coating materials of aged soot particles changed from secondary inorganic‐dominated to organic‐dominated species during their long‐range transport, which suggests the aqueous formation of secondary organic aerosols on soot‐containing particles. The thick organic coating formation in some particles further induced soot redistribution from the particle center into the coating. We highlight that the D f at 1.83‐1.93 is appropriate for assessing radiative absorption of long‐range transported soot particles in Eastern China and propose that soot redistribution may offset ∼13% optical absorption enhancement for long‐range transported soot particles. The microscopic changes in aged soot particles should be considered to precisely evaluate their optical absorption in the large‐scale haze layer.
The atmosphere over the ocean is an important research field that involves multiple aspects such as climate change, atmospheric pollution, weather forecasting, and marine ecosystems. It is of great significance for global sustainable development. Satellites provide a wide range of measurements of marine aerosol optical properties and are very important to the study of aerosol characteristics over the ocean. In this study, aerosol optical depth (AOD) data from seventeen AERONET (Aerosol Robotic Network) stations were used as benchmark data to comprehensively evaluate the data accuracy of six aerosol optical thickness products from 2013 to 2020, including MODIS (Moderate-resolution Imaging Spectrometer), VIIRS (Visible Infrared Imaging Radiome-ter Suite), MISR (Multi-Angle Imaging Spectrometer), OMAERO (OMI/Aura Multi-wavelength algorithm), OMAERUV (OMI/Aura Near UV algorithm), and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) in the East Asian Ocean. In the East Asia Sea, VIIRS AOD products generally have a higher correlation coefficient (R), expected error within ratio (EE within), lower root mean square error (RMSE), and median bias (MB) than MODIS AOD products. The retrieval accuracy of AOD data from VIIRS is the highest in spring. MISR showed a higher EE than other products in the East Asian Ocean but also exhibited systematic underestimation. In most cases, the OMAERUV AOD product data are of better quality than OMAERO, and OMAERO overestimates AOD throughout the year. The CALIPSO AOD product showed an apparent underestimation of the AOD in different seasons (EE Below = 58.98%), but when the AOD range is small (0 < AOD < 0.1), the CALIPSO data accuracy is higher compared with other satellite products under small AOD range. In the South China Sea, VIIRS has higher data accuracy than MISR, while in the Bohai-Yellow Sea, East China Sea, Sea of Japan, and the western Pacific Ocean, MISR has the best data accuracy. MODIS and VIIRS show similar trends in R, EE within, MB, and RMSE under the influence of AOD, Angstrom exponent (AE), and precipitable water. The study on the temporal and spatial distribution of AOD in the East Asian Ocean shows that the annual variation of AOD is different in different sea areas, and the ocean in the coastal area is greatly affected by land-based pollution. In contrast, the AOD values in the offshore areas are lower, and the aerosol type is mainly clean marine type aerosol. These findings can help researchers in the East Asian Ocean choose the most accurate and reliable satellite AOD data product to better study atmospheric aerosols' impact and trends.
An assessment is made of each component of the heat budgets of the surface and of the earth-atmosphere system in the central Arctic, both for an ice-covered ocean and for an ice-free ocean. The annual patterns of atmospheric heat loss for both conditions are obtained as residuals; the relation of these patterns to general atmospheric circulation and glacier accumulation is discussed.
It is shown that atmospheric cooling in the Arctic is closely related to certain indices of atmospheric circulation. An ice-free Arctic Ocean would probably be associated with atmospheric circulation more vigorous in summer at subarctic latitudes and of comparable vigor in winter. The cool summers and warm, moist winters would be highly conducive to glacier growth.
Particulate elemental carbon is found in the atmosphere in both urban and remote regions and isoften responsible for much of the absorption of solar radiation by atmospheric aerosols. Itsatmospheric lifetime is controlled by four factors: the initial size distribution, the concentrationof ambient particles, the frequency and duration of precipitation, and the efficiencies of removalmechanisms. A model of the atmospheric cycle of particulate elemental carbon which includesthese factors has been used to estimate the range of atmospheric lifetimes expected under variousconditions. Calculated lifetimes range from under 40 hours in rainy climates to well over 1 weekin clean, dry regions. DOI: 10.1111/j.1600-0889.1983.tb00027.x
Simultaneous aerosol measurements with particle counters and a multiwavelength integrating nephelometer have been made at Ny-Alesund, Svalbard (12° E, 79° N). The measured integral aerosol properties were used in an inversion procedure to derive a consistent model of the particle size distribution of Arctic haze. The obtained size distribution is compared to the global background aerosol size distribution. Both the light scattering coefficients and the total suspended volume of particles were found to be on the level of the global background. DOI: 10.1111/j.2153-3490.1980.tb00952.x