Journal articles on the topic 'Atmospheric aerosol formation'
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1
Park, Ki-Tae, Sehyun Jang, Kitack Lee, Young Jun Yoon, Min-Seob Kim, Kihong Park, Hee-Joo Cho, et al. "Observational evidence for the formation of DMS-derived aerosols during Arctic phytoplankton blooms." Atmospheric Chemistry and Physics 17, no. 15 (August 10, 2017): 9665–75. http://dx.doi.org/10.5194/acp-17-9665-2017.
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Abstract. The connection between marine biogenic dimethyl sulfide (DMS) and the formation of aerosol particles in the Arctic atmosphere was evaluated by analyzing atmospheric DMS mixing ratio, aerosol particle size distribution and aerosol chemical composition data that were concurrently collected at Ny-Ålesund, Svalbard (78.5° N, 11.8° E), during April and May 2015. Measurements of aerosol sulfur (S) compounds showed distinct patterns during periods of Arctic haze (April) and phytoplankton blooms (May). Specifically, during the phytoplankton bloom period the contribution of DMS-derived SO42− to the total aerosol SO42− increased by 7-fold compared with that during the proceeding Arctic haze period, and accounted for up to 70 % of fine SO42− particles (< 2.5 µm in diameter). The results also showed that the formation of submicron SO42− aerosols was significantly associated with an increase in the atmospheric DMS mixing ratio. More importantly, two independent estimates of the formation of DMS-derived SO42− aerosols, calculated using the stable S-isotope ratio and the non-sea-salt SO42− ∕ methanesulfonic acid ratio, respectively, were in close agreement, providing compelling evidence that the contribution of biogenic DMS to the formation of aerosol particles was substantial during the Arctic phytoplankton bloom period.
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Girgzdys, A., A. Juozaitis, and V. Ulevicius. "Atmospheric aerosol formation research." Journal of Aerosol Science 20, no. 8 (January 1989): 1107–9. http://dx.doi.org/10.1016/0021-8502(89)90773-8.
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Tian, Pengfei, Lei Zhang, Jianmin Ma, Kai Tang, Lili Xu, Yuan Wang, Xianjie Cao, et al. "Radiative absorption enhancement of dust mixed with anthropogenic pollution over East Asia." Atmospheric Chemistry and Physics 18, no. 11 (June 4, 2018): 7815–25. http://dx.doi.org/10.5194/acp-18-7815-2018.
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Abstract. The particle mixing state plays a significant yet poorly quantified role in aerosol radiative forcing, especially for the mixing of dust (mineral absorbing) and anthropogenic pollution (black carbon absorbing) over East Asia. We have investigated the absorption enhancement of mixed-type aerosols over East Asia by using the Aerosol Robotic Network observations and radiative transfer model calculations. The mixed-type aerosols exhibit significantly enhanced absorbing ability than the corresponding unmixed dust and anthropogenic aerosols, as revealed in the spectral behavior of absorbing aerosol optical depth, single scattering albedo, and imaginary refractive index. The aerosol radiative efficiencies for the dust, mixed-type, and anthropogenic aerosols are −101.0, −112.9, and −98.3 Wm-2τ-1 at the bottom of the atmosphere (BOA); −42.3, −22.5, and −39.8 Wm-2τ-1 at the top of the atmosphere (TOA); and 58.7, 90.3, and 58.5 Wm-2τ-1 in the atmosphere (ATM), respectively. The BOA cooling and ATM heating efficiencies of the mixed-type aerosols are significantly higher than those of the unmixed aerosol types over the East Asia region, resulting in atmospheric stabilization. In addition, the mixed-type aerosols correspond to a lower TOA cooling efficiency, indicating that the cooling effect by the corresponding individual aerosol components is partially counteracted. We conclude that the interaction between dust and anthropogenic pollution not only represents a viable aerosol formation pathway but also results in unfavorable dispersion conditions, both exacerbating the regional air pollution in East Asia. Our results highlight the necessity to accurately account for the mixing state of aerosols in atmospheric models over East Asia in order to better understand the formation mechanism for regional air pollution and to assess its impacts on human health, weather, and climate.
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Bauer, S. E., D. Koch, N. Unger, S. M. Metzger, D. T. Shindell, and D. G. Streets. "Nitrate aerosols today and in 2030: a global simulation including aerosols and tropospheric ozone." Atmospheric Chemistry and Physics 7, no. 19 (October 2, 2007): 5043–59. http://dx.doi.org/10.5194/acp-7-5043-2007.
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Abstract. Nitrate aerosols are expected to become more important in the future atmosphere due to the expected increase in nitrate precursor emissions and the decline of ammonium-sulphate aerosols in wide regions of this planet. The GISS climate model is used in this study, including atmospheric gas- and aerosol phase chemistry to investigate current and future (2030, following the SRES A1B emission scenario) atmospheric compositions. A set of sensitivity experiments was carried out to quantify the individual impact of emission- and physical climate change on nitrate aerosol formation. We found that future nitrate aerosol loads depend most strongly on changes that may occur in the ammonia sources. Furthermore, microphysical processes that lead to aerosol mixing play a very important role in sulphate and nitrate aerosol formation. The role of nitrate aerosols as climate change driver is analyzed and set in perspective to other aerosol and ozone forcings under pre-industrial, present day and future conditions. In the near future, year 2030, ammonium nitrate radiative forcing is about −0.14 W/m² and contributes roughly 10% of the net aerosol and ozone forcing. The present day nitrate and pre-industrial nitrate forcings are −0.11 and −0.05 W/m², respectively. The steady increase of nitrate aerosols since industrialization increases its role as a non greenhouse gas forcing agent. However, this impact is still small compared to greenhouse gas forcings, therefore the main role nitrate will play in the future atmosphere is as an air pollutant, with annual mean near surface air concentrations, in the fine particle mode, rising above 3 μg/m³ in China and therefore reaching pollution levels, like sulphate aerosols.
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Davidi, A., I. Koren, and L. Remer. "Direct measurements of the effect of biomass burning over the Amazon on the atmospheric temperature profile." Atmospheric Chemistry and Physics Discussions 9, no. 3 (May 15, 2009): 12007–25. http://dx.doi.org/10.5194/acpd-9-12007-2009.
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Abstract. Aerosols suspended in the atmosphere interact with the solar radiation and thus change the radiation energy fluxes in the atmospheric column. In particular, absorbing aerosols can stabilize the lower atmosphere by warming the aerosol layer; while cooling both: the layers beneath and the surface. Changes in atmospheric stability can affect cloud formation and cloud properties. In this paper we measure changes in the atmospheric temperature profile as a function of the smoke loading and the cloudiness over the Amazon basin, during the dry seasons (August and September) of 2005–2007. We show that as the aerosol optical depth (AOD) increases from 0.02 to a value of ~0.6, there is a decrease of ~4.3°C at 1000 hPa, and an increase of ~1.6°C at 850 hPa. The warming of the aerosol layer at 850 hPa is likely due to aerosol absorption when the particles are exposed to direct illumination by the sun. The large values of cooling in the lower layers are explained by a combination of aerosol extinction of the solar flux in the layers aloft and by an aerosol-induced increase of cloud cover and further shading of the lower atmosphere. We estimate that the increase in cloud fraction due to aerosol contributes about half of the observed cooling in the lower layers.
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Joutsensaari, J., M. Loivamäki, T. Vuorinen, P. Miettinen, A. M. Nerg, J. K. Holopainen, and A. Laaksonen. "Nanoparticle formation by ozonolysis of inducible plant volatiles." Atmospheric Chemistry and Physics 5, no. 6 (June 16, 2005): 1489–95. http://dx.doi.org/10.5194/acp-5-1489-2005.
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Abstract. We present the first laboratory experiments of aerosol formation from oxidation of volatile organic species emitted by living plants, a process which for half a century has been known to take place in the atmosphere. We have treated white cabbage plants with methyl jasmonate in order to induce the production of monoterpenes and certain less-volatile sesqui- and homoterpenes. Ozone was introduced into the growth chamber in which the plants were placed, and the subsequent aerosol formation and growth of aerosols were monitored by measuring the particle size distributions continuously during the experiments. Our observations show similar particle formation rates as in the atmosphere but much higher growth rates. The results indicate that the concentrations of nonvolatile oxidation products of plant released precursors needed to induce the nucleation are roughly an order-of-magnitude higher than their concentrations during atmospheric nucleation events. Our results therefore suggest that if oxidized organics are involved in atmospheric nucleation events, their role is to participate in the growth of pre-existing molecular clusters rather than to form such clusters through homogeneous or ion-induced nucleation.
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Eleftheriadis, K., Meng-Chen Chung, and I. Colbeck. "Atmospheric aerosol formation over Athens." Journal of Aerosol Science 29 (September 1998): S25—S26. http://dx.doi.org/10.1016/s0021-8502(98)00089-5.
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Arnold, Frank. "Atmospheric Ions and Aerosol Formation." Space Science Reviews 137, no. 1-4 (June 2008): 225–39. http://dx.doi.org/10.1007/s11214-008-9390-8.
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Liu, Jiumeng, Liz Alexander, Jerome D. Fast, Rodica Lindenmaier, and John E. Shilling. "Aerosol characteristics at the Southern Great Plains site during the HI-SCALE campaign." Atmospheric Chemistry and Physics 21, no. 6 (March 31, 2021): 5101–16. http://dx.doi.org/10.5194/acp-21-5101-2021.
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Abstract. Large uncertainties exist in global climate model predictions of radiative forcing due to insufficient understanding and simplified numerical representation of cloud formation and cloud–aerosol interactions. The Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems (HI-SCALE) campaign was conducted near the DOE's Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in north-central Oklahoma to provide a better understanding of land–atmosphere interactions, aerosol and cloud properties, and the influence of aerosol and land–atmosphere interactions on cloud formation. The HI-SCALE campaign consisted of two intensive observational periods (IOPs) (April–May and August–September, 2016), during which coincident measurements were conducted both on the G-1 aircraft platform and at the SGP ground site. In this study we focus on the observations at the SGP ground site. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and an Ionicon proton-transfer-reaction mass spectrometer (PTR-MS) were deployed, characterizing chemistry of non-refractory aerosol and trace gases, respectively. Contributions from various aerosol sources, including biogenic and biomass burning emissions, were retrieved using factor analysis of the AMS data. In general, the organic aerosols at the SGP site was highly oxidized, with oxygenated organic aerosol (OOA) identified as the dominant factor for both the spring and summer IOP though more aged in spring. Cases of isoprene-epoxydiol-derived secondary organic aerosol (IEPOX SOA) and biomass burning events were further investigated to understand additional sources of organic aerosol. Unlike other regions largely impacted by IEPOX chemistry, the IEPOX SOA at SGP was more highly oxygenated, likely due to the relatively weak local emissions of isoprene. Biogenic emissions appear to largely control the formation of organic aerosol (OA) during the HI-SCALE campaign. Potential HOM (highly oxygenated molecule) chemistry likely contributes to the highly oxygenated feature of aerosols at the SGP site, with impacts on new particle formation and global climate.
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Bauer, S. E., D. Koch, N. Unger, S. M. Metzger, D. T. Shindell, and D. G. Streets. "Nitrate aerosols today and in 2030: importance relative to other aerosol species and tropospheric ozone." Atmospheric Chemistry and Physics Discussions 7, no. 2 (April 26, 2007): 5553–93. http://dx.doi.org/10.5194/acpd-7-5553-2007.
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Abstract. Ammonium-nitrate aerosols are expected to become more important in the future atmosphere due to the expected increase in nitrate precursor emissions and the decline of ammonium-sulphate aerosols in wide regions of this planet. The GISS climate model is used in this study, including atmospheric gas- and aerosol phase chemistry to investigate current and future (2030, following the SRES A1B emission scenario) atmospheric compositions. A set of sensitivity experiments was carried out to quantify the individual impact of emission- and physical climate change on nitrate aerosol formation. We found that future nitrate aerosol loads depend most strongly on changes that may occur in the ammonia sources. Furthermore, microphysical processes that lead to aerosol mixing play a very important role in sulphate and nitrate aerosol formation. The role of nitrate aerosols as climate change driver is analyzed and set in perspective to other aerosol and ozone forcings under pre-industrial, present day and future conditions. In the near future, year 2030, ammonium nitrate radiative forcing is about –0.14 W/m2 and contributes roughly 10% of the net aerosol and ozone forcing. The present day nitrate and pre-industrial nitrate forcings are –0.11 and –0.05 W/m2, respectively. The steady increase of nitrate aerosols since industrialization increases its role as a non greenhouse gas forcing agent. However, this impact is still small compared to greenhouse gas forcings, therefore the main role nitrate will play in the future atmosphere is as an air pollutant, with annual mean near surface air concentrations rising above 3 μg/m3 in China and therefore reaching pollution levels, like sulphate aerosols, in the fine particle mode.
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Pirjola, L. "Effects of aerosol dynamics on atmospheric aerosol formation." Journal of Aerosol Science 32 (September 2001): 357–62. http://dx.doi.org/10.1016/s0021-8502(01)00099-4.
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Jaenicke, Ruprecht, Sabine Matthias-Maser, and Sabine Gruber. "Omnipresence of biological material in the atmosphere." Environmental Chemistry 4, no. 4 (2007): 217. http://dx.doi.org/10.1071/en07021.
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Environmental context. Atmospheric biological particles have been largely overlooked in the past. While some microorganisms have been studied, the majority of other biological particles have not. The presence of these particles might force us to view the atmospheric aerosol differently. Abstract. Measurements of biological particles in the atmosphere during the last decade indicate that the presence of these particles seems to have been underestimated by atmospheric scientists. On the average these primary aerosol particles might be present as much as 25% of the total mass (or number for particles with radius greater than 0.2 µm) concentration of the atmospheric aerosol. Such a large fraction certainly plays a major role in all processes affected by atmospheric aerosols, such as cloud and precipitation formation, climate forcing, visibility, turbidity, and so on. This disregard of the biological particles requires a new attitude in our opinion.
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Hatzianastassiou, N., C. Matsoukas, A. Fotiadi, P. Koepke, K. G. Pavlakis, and I. Vardavas. "Modelling the direct effect of aerosols in the solar near-infrared on a planetary scale." Atmospheric Chemistry and Physics 7, no. 12 (June 25, 2007): 3211–29. http://dx.doi.org/10.5194/acp-7-3211-2007.
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Abstract. We used a spectral radiative transfer model to compute the direct radiative effect (DRE) of natural plus anthropogenic aerosols in the solar near-infrared (IR), between 0.85–10 μm, namely, their effect on the outgoing near-IR radiation at the top of atmosphere (TOA, ΔFTOA), on the atmospheric absorption of near-IR radiation (ΔFatmab) and on the surface downward and absorbed near-IR radiation (ΔFsurf, and ΔFsurfnet, respectively). The computations were performed on a global scale (over land and ocean) under all-sky conditions, using detailed spectral aerosol optical properties taken from the Global Aerosol Data Set (GADS) supplemented by realistic data for the rest of surface and atmospheric parameters. The computed aerosol DRE, averaged over the 12-year period 1984–1995 for January and July, shows that on a global mean basis aerosols produce a planetary cooling by increasing the scattered near-IR radiation back to space by 0.48 W m−2, they warm the atmosphere by 0.37 W m−2 and cool the surface by decreasing the downward and absorbed near-IR radiation at surface by 1.03 and 0.85 W m−2, respectively. The magnitude of the near-IR aerosol DRE is smaller than that of the combined ultraviolet (UV) and visible DRE, but it is still energetically important, since it contributes to the total shortwave (SW) DRE by 22–31%. The aerosol-produced near-IR surface cooling combined with the atmospheric warming, may affect the thermal dynamics of the Earth-atmosphere system, by increasing the atmospheric stability, decreasing thus cloud formation, and precipitation, especially over desertification threatened regions such as the Mediterranean basin. This, together with the fact that the sign of near-IR aerosol DRE is sometimes opposite to that of UV-visible DRE, demonstrates the importance of performing detailed spectral computations to provide estimates of the climatic role of aerosols for the Earth-atmosphere system. This was demonstrated by sensitivity tests revealing very large differences (up to 300%) between aerosol DREs computed using detailed spectral and spectrally-averaged aerosol optical properties. Our model results indicate thus that the aerosol direct radiative effect on the near-IR radiation is very sensitive to the treatment of the spectral dependence of aerosol optical properties and solar radiation.
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Hao, Liqing, Olga Garmash, Mikael Ehn, Pasi Miettinen, Paola Massoli, Santtu Mikkonen, Tuija Jokinen, et al. "Combined effects of boundary layer dynamics and atmospheric chemistry on aerosol composition during new particle formation periods." Atmospheric Chemistry and Physics 18, no. 23 (December 13, 2018): 17705–16. http://dx.doi.org/10.5194/acp-18-17705-2018.
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Abstract. Characterizing aerosol chemical composition in response to meteorological changes and atmospheric chemistry is important to gain insights into new particle formation mechanisms. A BAECC (Biogenic Aerosols – Effects on Clouds and Climate) campaign was conducted during the spring 2014 at the SMEAR II station (Station for Measuring Forest Ecosystem–Aerosol Relations) in Finland. The particles were characterized by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). A PBL (planetary boundary layer) dilution model was developed to assist interpreting the measurement results. Right before nucleation events, the mass concentrations of organic and sulfate aerosol species were both decreased rapidly along with the growth of PBL heights. However, the mass fraction of sulfate aerosol of the total aerosol mass was increased, in contrast to a decrease for the organic mass fraction. Meanwhile, an increase in LVOOA (low-volatility oxygenated organic aerosol) mass fraction of the total organic mass was observed, in distinct comparison to a reduction of SVOOA (semi-volatile OOA) mass fraction. Our results demonstrate that, at the beginning of nucleation events, the observed sulfate aerosol mass was mainly driven by vertical turbulent mixing of sulfate-rich aerosols between the residual layer and the newly formed boundary layer, while the condensation of sulfuric acid (SA) played a minor role in interpreting the measured sulfate mass concentration. For the measured organic aerosols, their temporal profiles were mainly driven by dilution from PBL development, organic aerosol mixing in different boundary layers and/or partitioning of organic vapors, but accurate measurements of organic vapor concentrations and characterization on the spatial aerosol chemical composition are required. In general, the observed aerosol particles by AMS are subjected to joint effects of PBL dilution, atmospheric chemistry and aerosol mixing in different boundary layers. During aerosol growth periods in the nighttime, the mass concentrations of organic aerosols and organic nitrate aerosols were both increased. The increase in SVOOA mass correlated well with the calculated increase in condensed HOMs' (highly oxygenated organic molecules) mass. To our knowledge, our results are the first atmospheric observations showing a connection between increase in SVOOA and condensed HOMs during the nighttime.
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Prisle, N. L., M. Dal Maso, and H. Kokkola. "A simple representation of surface active organic aerosol in cloud droplet formation." Atmospheric Chemistry and Physics 11, no. 9 (May 4, 2011): 4073–83. http://dx.doi.org/10.5194/acp-11-4073-2011.
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Abstract. Atmospheric aerosols often contain surface active organics. Surface activity can affect cloud droplet formation through both surface partitioning and surface tension reduction in activating droplets. However, a comprehensive thermodynamic account for these effects in Köhler modeling is computationally demanding and requires knowledge of both droplet composition and component molecular properties, which is generally unavailable. Here, a simple representation of activation properties for surface active organics is introduced and compared against detailed model predictions and laboratory measurements of CCN activity for mixed surfactant-salt particles from the literature. This simple organic representation is seen to work well for aerosol organic-inorganic composition ranges typically found in the atmosphere, and agreement with both experiments and detailed model predictions increases with surfactant strength. The simple representation does not require resolution of the organic aerosol composition and relies solely on properties of the organic fraction that can be measured directly with available techniques. It can thus potentially be applied to complex and ambient surface active aerosols. It is not computationally demanding, and therefore has high potential for implementation to atmospheric models accounting for cloud microphysics.
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Murphy, S. M., A. Sorooshian, J. H. Kroll, N. L. Ng, P. Chhabra, C. Tong, J. D. Surratt, E. Knipping, R. C. Flagan, and J. H. Seinfeld. "Secondary aerosol formation from atmospheric reactions of aliphatic amines." Atmospheric Chemistry and Physics Discussions 7, no. 1 (January 10, 2007): 289–349. http://dx.doi.org/10.5194/acpd-7-289-2007.
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Abstract. Although aliphatic amines have been detected in both urban and rural atmospheric aerosols, little is known about the chemistry leading to particle formation or the potential aerosol yields from reactions of gas-phase amines. We present here the first systematic study of aerosol formation from the atmospheric reactions of amines. Based on laboratory chamber experiments and theoretical calculations, we evaluate aerosol formation from reaction of OH, ozone, and nitric acid with trimethylamine, methylamine, triethylamine, diethylamine, ethylamine, and ethanolamine. Entropies of formation for alkylammonium nitrate salts are estimated by molecular dynamics calculations enabling us to estimate equilibrium constants for the reactions of amines with nitric acid. Though subject to significant uncertainty, the calculated dissociation equilibrium constant for diethylammonium nitrate is found to be sufficiently small to allow for its atmospheric formation, even in the presence of ammonia which competes for available nitric acid. Experimental chamber studies indicate that the dissociation equilibrium constant for triethylammonium nitrate is of the same order of magnitude as that for ammonium nitrate. All amines studied form aerosol when photooxidized in the presence of NOx with the majority of the aerosol mass present at the peak of aerosol growth consisting of aminium (R3NH+) nitrate salts, which repartition back to the gas phase as the parent amine is consumed. Only the two tertiary amines studied, trimethylamine and triethylamine, are found to form significant non-salt organic aerosol when oxidized by OH or ozone; calculated organic mass yields for the experiments conducted are similar for ozonolysis (15% and 5% respectively) and photooxidation (23% and 8% respectively). The non-salt organic aerosol formed appears to be more stable than the nitrate salts and does not quickly repartition back to the gas phase.
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Murphy, S. M., A. Sorooshian, J. H. Kroll, N. L. Ng, P. Chhabra, C. Tong, J. D. Surratt, E. Knipping, R. C. Flagan, and J. H. Seinfeld. "Secondary aerosol formation from atmospheric reactions of aliphatic amines." Atmospheric Chemistry and Physics 7, no. 9 (May 8, 2007): 2313–37. http://dx.doi.org/10.5194/acp-7-2313-2007.
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Abstract. Although aliphatic amines have been detected in both urban and rural atmospheric aerosols, little is known about the chemistry leading to particle formation or the potential aerosol yields from reactions of gas-phase amines. We present here the first systematic study of aerosol formation from the atmospheric reactions of amines. Based on laboratory chamber experiments and theoretical calculations, we evaluate aerosol formation from reaction of OH, ozone, and nitric acid with trimethylamine, methylamine, triethylamine, diethylamine, ethylamine, and ethanolamine. Entropies of formation for alkylammonium nitrate salts are estimated by molecular dynamics calculations enabling us to estimate equilibrium constants for the reactions of amines with nitric acid. Though subject to significant uncertainty, the calculated dissociation equilibrium constant for diethylammonium nitrate is found to be sufficiently small to allow for its atmospheric formation, even in the presence of ammonia which competes for available nitric acid. Experimental chamber studies indicate that the dissociation equilibrium constant for triethylammonium nitrate is of the same order of magnitude as that for ammonium nitrate. All amines studied form aerosol when photooxidized in the presence of NOx with the majority of the aerosol mass present at the peak of aerosol growth consisting of aminium (R3NH+) nitrate salts, which repartition back to the gas phase as the parent amine is consumed. Only the two tertiary amines studied, trimethylamine and triethylamine, are found to form significant non-salt organic aerosol when oxidized by OH or ozone; calculated organic mass yields for the experiments conducted are similar for ozonolysis (15% and 5% respectively) and photooxidation (23% and 8% respectively). The non-salt organic aerosol formed appears to be more stable than the nitrate salts and does not quickly repartition back to the gas phase.
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Creamean, Jessie M., Gijs de Boer, Hagen Telg, Fan Mei, Darielle Dexheimer, Matthew D. Shupe, Amy Solomon, and Allison McComiskey. "Assessing the vertical structure of Arctic aerosols using balloon-borne measurements." Atmospheric Chemistry and Physics 21, no. 3 (February 9, 2021): 1737–57. http://dx.doi.org/10.5194/acp-21-1737-2021.
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Abstract. The rapidly warming Arctic is sensitive to perturbations in the surface energy budget, which can be caused by clouds and aerosols. However, the interactions between clouds and aerosols are poorly quantified in the Arctic, in part due to (1) limited observations of vertical structure of aerosols relative to clouds and (2) ground-based observations often being inadequate for assessing aerosol impacts on cloud formation in the characteristically stratified Arctic atmosphere. Here, we present a novel evaluation of Arctic aerosol vertical distributions using almost 3 years' worth of tethered balloon system (TBS) measurements spanning multiple seasons. The TBS was deployed at the U.S. Department of Energy Atmospheric Radiation Measurement Program's facility at Oliktok Point, Alaska. Aerosols were examined in tandem with atmospheric stability and ground-based remote sensing of cloud macrophysical properties to specifically address the representativeness of near-surface aerosols to those at cloud base. Based on a statistical analysis of the TBS profiles, ground-based aerosol number concentrations were unequal to those at cloud base 86 % of the time. Intermittent aerosol layers were observed 63 % of the time due to poorly mixed below-cloud environments, mostly found in the spring, causing a decoupling of the surface from the cloud layer. A uniform distribution of aerosol below cloud was observed only 14 % of the time due to a well-mixed below-cloud environment, mostly during the fall. The equivalent potential temperature profiles of the below-cloud environment reflected the aerosol profile 89 % of the time, whereby a mixed or stratified below-cloud environment was observed during a uniform or layered aerosol profile, respectively. In general, a combination of aerosol sources, thermodynamic structure, and wet removal processes from clouds and precipitation likely played a key role in establishing observed aerosol vertical structures. Results such as these could be used to improve future parameterizations of aerosols and their impacts on Arctic cloud formation and radiative properties.
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Joutsensaari, J., M. Loivamäki, T. Vuorinen, P. Miettinen, A. M. Nerg, J. K. Holopainen, and A. Laaksonen. "Nanoparticle formation by ozonolysis of inducible plant volatiles." Atmospheric Chemistry and Physics Discussions 5, no. 1 (January 10, 2005): 1–16. http://dx.doi.org/10.5194/acpd-5-1-2005.
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Abstract. We present the first laboratory experiments of aerosol formation from oxidation of volatile organic species emitted by living plants, a process which for half a century has been known to take place in the atmosphere. We have treated white cabbage crops with methyl jasmonate in order to induce the production of monoterpenes and certain less-volatile sesqui- and homoterpenes. Ozone was introduced into the growth chamber in which the crops were placed, and the subsequent aerosol formation and growth of aerosols were monitored by measuring the particle size distributions continuously during the experiments. Our observations show similar particle formation rates as in the atmosphere but much higher growth rates. The results indicate that the concentrations of nonvolatile oxidation products of plant released precursors needed to induce the nucleation are roughly an order-of-magnitude higher than their concentrations during atmospheric nucleation events. Our results therefore suggest that atmospheric nucleation events proceed via condensation of oxidized organics on pre-existing molecular clusters rather than via their homogeneous or ion-induced nucleation.
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Fung, Ka Ming, Colette L. Heald, Jesse H. Kroll, Siyuan Wang, Duseong S. Jo, Andrew Gettelman, Zheng Lu, et al. "Exploring dimethyl sulfide (DMS) oxidation and implications for global aerosol radiative forcing." Atmospheric Chemistry and Physics 22, no. 2 (February 1, 2022): 1549–73. http://dx.doi.org/10.5194/acp-22-1549-2022.
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Abstract. Aerosol indirect radiative forcing (IRF), which characterizes how aerosols alter cloud formation and properties, is very sensitive to the preindustrial (PI) aerosol burden. Dimethyl sulfide (DMS), emitted from the ocean, is a dominant natural precursor of non-sea-salt sulfate in the PI and pristine present-day (PD) atmospheres. Here we revisit the atmospheric oxidation chemistry of DMS, particularly under pristine conditions, and its impact on aerosol IRF. Based on previous laboratory studies, we expand the simplified DMS oxidation scheme used in the Community Atmospheric Model version 6 with chemistry (CAM6-chem) to capture the OH-addition pathway and the H-abstraction pathway and the associated isomerization branch. These additional oxidation channels of DMS produce several stable intermediate compounds, e.g., methanesulfonic acid (MSA) and hydroperoxymethyl thioformate (HPMTF), delay the formation of sulfate, and, hence, alter the spatial distribution of sulfate aerosol and radiative impacts. The expanded scheme improves the agreement between modeled and observed concentrations of DMS, MSA, HPMTF, and sulfate over most marine regions, based on the NASA Atmospheric Tomography (ATom), the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA), and the Variability of the American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) measurements. We find that the global HPMTF burden and the burden of sulfate produced from DMS oxidation are relatively insensitive to the assumed isomerization rate, but the burden of HPMTF is very sensitive to a potential additional cloud loss. We find that global sulfate burden under PI and PD emissions increase to 412 Gg S (+29 %) and 582 Gg S (+8.8 %), respectively, compared to the standard simplified DMS oxidation scheme. The resulting annual mean global PD direct radiative effect of DMS-derived sulfate alone is −0.11 W m−2. The enhanced PI sulfate produced via the gas-phase chemistry updates alone dampens the aerosol IRF as anticipated (−2.2 W m−2 in standard versus −1.7 W m−2, with updated gas-phase chemistry). However, high clouds in the tropics and low clouds in the Southern Ocean appear particularly sensitive to the additional aqueous-phase pathways, counteracting this change (−2.3 W m−2). This study confirms the sensitivity of aerosol IRF to the PI aerosol loading and the need to better understand the processes controlling aerosol formation in the PI atmosphere and the cloud response to these changes.
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Tsui, William G., Joseph L. Woo, and V. Faye McNeill. "Impact of Aerosol-Cloud Cycling on Aqueous Secondary Organic Aerosol Formation." Atmosphere 10, no. 11 (October 31, 2019): 666. http://dx.doi.org/10.3390/atmos10110666.
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Chemical processing of organic material in aqueous atmospheric aerosols and cloudwater is known to form secondary organic aerosols (SOA), although the extent to which each of these processes contributes to total aerosol mass is unclear. In this study, we use GAMMA 5.0, a photochemical box model with coupled gas and aqueous-phase chemistry, to consider the impact of aqueous organic reactions in both aqueous aerosols and clouds on isoprene epoxydiol (IEPOX) SOA over a range of pH for both aqueous phases, including cycling between cloud and aerosol within a single simulation. Low pH aqueous aerosol, in the absence of organic coatings or other morphology which may limit uptake of IEPOX, is found to be an efficient source of IEPOX SOA, consistent with previous work. Cloudwater at pH 4 or lower is also found to be a potentially significant source of IEPOX SOA. This phenomenon is primarily attributed to the relatively high uptake of IEPOX to clouds as a result of higher water content in clouds as compared with aerosol. For more acidic cloudwater, the aqueous organic material is comprised primarily of IEPOX SOA and lower-volatility organic acids. Both cloudwater pH and the time of day or sequence of aerosol-to-cloud or cloud-to-aerosol transitions impacted final aqueous SOA mass and composition in the simulations. The potential significance of cloud processing as a contributor to IEPOX SOA production could account for discrepancies between predicted IEPOX SOA mass from atmospheric models and measured ambient IEPOX SOA mass, or observations of IEPOX SOA in locations where mass transfer limitations are expected in aerosol particles.
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Zhang, Haofei, Ying-Hsuan Lin, Zhenfa Zhang, Xiaolu Zhang, Stephanie L. Shaw, Eladio M. Knipping, Rodney J. Weber, Avram Gold, Richard M. Kamens, and Jason D. Surratt. "Secondary organic aerosol formation from methacrolein photooxidation: roles of NOx level, relative humidity and aerosol acidity." Environmental Chemistry 9, no. 3 (2012): 247. http://dx.doi.org/10.1071/en12004.
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Environmental contextSecondary organic aerosols formed from the oxidation of volatile organic compounds make a significant contribution to atmospheric particulate matter, which in turn affects both global climate change and human health. We investigate the mechanisms of formation and the chemical properties of secondary organic aerosols derived from isoprene, the most abundant non-methane-based, volatile organic compound emitted into the Earth’s atmosphere. However, the exact manner in which these aerosols are formed, and how they are affected by environmental conditions, remains unclear. AbstractSecondary organic aerosol (SOA) formation from the photooxidation of methacrolein (MACR) was examined in a dual outdoor smog chamber under varied initial nitric oxide (NO) levels, relative humidities (RHs) and seed aerosol acidities. Aerosol sizing measurements and off-line chemical analyses by gas chromatography/mass spectrometry and ultra performance liquid chromatography/electrospray ionisation high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS) were used to characterise MACR SOA formation. Results indicate that both SOA mass and chemical composition largely depend on the initial MACR/NO ratio and RH conditions. Specifically, at lower initial NO levels (MACR/NO = ~2.7) more substantial SOA is formed under dry conditions (5–20 % RH) compared to wet conditions (30–80 % RH). However, at higher initial NO levels (MACR/NO = ~0.9), the maximum SOA formation was marginally higher under wet conditions. Furthermore, UPLC/ESI-HR-Q-TOFMS data suggest that most particle-phase oligomers, which have been previously observed to form from the oxidation of methacryloylperoxynitrate, were enhanced under dry conditions. In addition to 2-methylglyceric acid and organosulfates derived from MACR oxidation, a nitrogen-containing organic tracer compound was found to form substantially in both chamber-generated and ambient aerosol samples collected from downtown Atlanta, GA, during the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS). Moreover, increasing aerosol acidity because of additional sulfuric acid appears to have a negligible effect on both SOA mass and most SOA constituents. Nevertheless, increased RH and aerosol acidity were both observed to enhance organosulfate formation; however, elevating RH mediates organosulfate formation, suggesting that wet sulfate aerosols are necessary to form organosulfates in atmospheric aerosols.
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Wang, H., G. Y. Shi, X. Y. Zhang, S. L. Gong, S. C. Tan, B. Chen, H. Z. Che, and T. Li. "Mesoscale modelling study of the interactions between aerosols and PBL meteorology during a haze episode in China Jing–Jin–Ji and its near surrounding region – Part 2: Aerosols' radiative feedback effects." Atmospheric Chemistry and Physics 15, no. 6 (March 23, 2015): 3277–87. http://dx.doi.org/10.5194/acp-15-3277-2015.
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Abstract. Two model experiments, namely a control (CTL) experiment without aerosol–radiation feedbacks and a experiment with online aerosol–radiation (RAD) interactions, were designed to study the radiative feedback on regional radiation budgets, planetary boundary layer (PBL) meteorology and haze formation due to aerosols during haze episodes over Jing–Jin–Ji, China, and its near surroundings (3JNS region of China: Beijing, Tianjin, Hebei, East Shanxi, West Shandong and North Henan) with a two-way atmospheric chemical transport model. The impact of aerosols on solar radiation reaching Earth's surface, outgoing long-wave emission at the top of the atmosphere, air temperature, PBL turbulence diffusion, PBL height, wind speeds, air pressure pattern and PM2.5 has been studied focusing on a haze episode during the period from 7 to 11 July 2008. The results show that the mean solar radiation flux that reaches the ground decreases by about 15% in 3JNS and 20 to 25%in the region with the highest aerosol optical depth during the haze episode. The fact that aerosol cools the PBL atmosphere but warms the atmosphere above it leads to a more stable atmospheric stratification over the region, which causes a decrease in turbulence diffusion of about 52% and a decrease in the PBL height of about 33%. This consequently forms a positive feedback on the particle concentration within the PBL and the surface as well as the haze formation. Additionally, aerosol direct radiative forcing (DRF) increases PBL wind speed by about 9% and weakens the subtropical high by about 14 hPa, which aids the collapse of haze pollution and results in a negative feedback to the haze episode. The synthetic impacts from the two opposite feedbacks result in about a 14% increase in surface PM2.5. However, the persistence time of both high PM2.5 and haze pollution is not affected by the aerosol DRF. On the contrary over offshore China, aerosols heat the PBL atmosphere and cause unstable atmospheric stratification, but the impact and its feedback on the planetary boundary layer height, turbulence diffusion and wind is weak, with the exception of the evident impacts on the subtropical high.
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Tsigaridis, K., M. Krol, F. J. Dentener, Y. Balkanski, J. Lathière, S. Metzger, D. A. Hauglustaine, and M. Kanakidou. "Change in global aerosol composition since preindustrial times." Atmospheric Chemistry and Physics 6, no. 12 (November 10, 2006): 5143–62. http://dx.doi.org/10.5194/acp-6-5143-2006.
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Abstract. To elucidate human induced changes of aerosol load and composition in the atmosphere, a coupled aerosol and gas-phase chemistry transport model of the troposphere and lower stratosphere has been used. The present 3-D modeling study focuses on aerosol chemical composition change since preindustrial times considering the secondary organic aerosol formation together with all other main aerosol components including nitrate. In particular, we evaluate non-sea-salt sulfate (nss-SO4=), ammonium (NH4+), nitrate (NO3−), black carbon (BC), sea-salt, dust, primary and secondary organics (POA and SOA) with a focus on the importance of secondary organic aerosols. Our calculations show that the aerosol optical depth (AOD) has increased by about 21% since preindustrial times. This enhancement of AOD is attributed to a rise in the atmospheric load of BC, nss-SO4=, NO3
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Jones, T. A., S. A. Christopher, and J. Quaas. "A six year satellite-based assessment of the regional variations in aerosol indirect effects." Atmospheric Chemistry and Physics Discussions 8, no. 6 (December 5, 2008): 20349–97. http://dx.doi.org/10.5194/acpd-8-20349-2008.
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Abstract. Since aerosols act as cloud condensation nuclei (CCN) for cloud water droplets, changes in aerosol concentrations having significant impacts on the corresponding cloud properties. An increase in aerosol concentration leads to an increase in CCN, with an associated decrease in cloud droplet size for a given cloud liquid water content. Smaller droplet sizes may then lead to a reduction in precipitation efficiency and an increase in cloud lifetimes, which induces more reflection of solar radiation back into space, cooling the atmosphere below the cloud layer. In reality, this relationship is much more complex and is interrelated between aerosol, cloud, and atmospheric conditions present at any one time. MODIS aerosol and cloud properties are combined with NCEP Reanalysis data for eight different regions around the globe between March 2000 and December 2005 to study the effects of different aerosol, cloud, and atmospheric conditions on the aerosol indirect effect (AIE). The first AIE for both anthropogenic and dust aerosols is calculated so that the importance of each can be compared. The unique aspect of this research is that it combines multiple satellite data sets over a six year period to provide a comprehensive analysis of indirect effects for different aerosol regimes around the globe. Results show that in most regions, AIE has a distinct seasonal cycle, though the cycle varies in significance and period from region to region. In the Arabian Sea, the six-year mean anthropogenic + dust AIE is −0.4 Wm−2 and is greatest during the summer months (<−2.0 Wm−2) during which dust aerosol concentration is greatest, significant concentrations of anthropogenic aerosols are present, and upward vertical motion is also present providing a favorable environment for cloud formation. In the Bay of Bengal, AIE was negligible owing to less favorable atmospheric conditions and a lower concentration of aerosols. In the eastern North Atlantic, AIE was also small (<0.1 Wm−2) and in this region dust aerosol concentration is much greater than the anthropogenic or sea salt components. However, elevated dust in this region may also absorb solar radiation and warm the atmosphere, stabilizing the atmosphere as evidenced by weak vertical motion during the summer (0.02 Pa s−1) when AOT is greatest. Lower average cloud fraction compared to other regions allows the absorbing effect to offset the cooling effect associated with increasing CCN. The western Atlantic and Pacific oceans have large anthropogenic aerosol concentrations transported from the United States and China respectively and produce modest anthropogenic AIE (0.7, 0.9 Wm−2) in these regions as expected. Anthropogenic AIE was also present off the West African coast corresponding to aerosols produced from seasonal biomass burning. Interestingly, atmospheric conditions were not particularly favorable for cloud formation compared to the other regions during the times where AIE was observed. Overall, we are able to conclude that aerosol type, atmospheric conditions and their relative vertical distributions are a key factors as to whether or not significant AIE occurs and simple correlations between AOT and cloud properties are insufficient to explain the AIE.
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Stevens, R. G., J. R. Pierce, C. A. Brock, M. K. Reed, J. H. Crawford, J. S. Holloway, T. B. Ryerson, L. G. Huey, and J. B. Nowak. "Nucleation and growth of sulfate aerosol in coal-fired power plant plumes: sensitivity to background aerosol and meteorology." Atmospheric Chemistry and Physics 12, no. 1 (January 3, 2012): 189–206. http://dx.doi.org/10.5194/acp-12-189-2012.
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Abstract. New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulfur sources may be an important source of particles in the atmosphere. It remains unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are 10s of kilometers and larger. The predictive power of these models is thus limited by the resultant uncertainties in aerosol size distributions. In this paper, we focus on sub-grid sulfate aerosol processes within coal-fired power plant plumes: the sub-grid oxidation of SO2 with condensation of H2SO4 onto newly-formed and pre-existing particles. We have developed a modeling framework with aerosol microphysics in the System for Atmospheric Modelling (SAM), a Large-Eddy Simulation/Cloud-Resolving Model (LES/CRM). The model is evaluated against aircraft observations of new-particle formation in two different power-plant plumes and reproduces the major features of the observations. We show how the downwind plume aerosols can be greatly modified by both meteorological and background aerosol conditions. In general, new-particle formation and growth is greatly reduced during polluted conditions due to the large pre-existing aerosol surface area for H2SO4 condensation and particle coagulation. The new-particle formation and growth rates are also a strong function of the amount of sunlight and NOx since both control OH concentrations. The results of this study highlight the importance for improved sub-grid particle formation schemes in regional and global aerosol models.
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Prisle, N. L., M. Dal Maso, and H. Kokkola. "A simple representation of surface active organic aerosol in cloud droplet formation." Atmospheric Chemistry and Physics Discussions 10, no. 10 (October 11, 2010): 23601–25. http://dx.doi.org/10.5194/acpd-10-23601-2010.
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Abstract. Atmospheric aerosols often contain surface active organics. Surface activity can affect cloud droplet formation through both surface partitioning and surface tension reduction in activating droplets. However, a comprehensive thermodynamic account for these effects in Köhler modeling is computationally demanding and requires knowledge of both droplet composition and component molecular properties, which is generally unavailable. Here, a simple representation of activation properties for surface active organics is introduced and compared against detailed model predictions and laboratory measurements of CCN activity for mixed surfactant-salt particles from the literature. This simple organic representation is seen to work well for aerosol organic-inorganic composition ranges typically found in the atmosphere, and agreement with both experiments and detailed model predictions increases with surfactant strength. The simple representation does not require resolution of the organic aerosol composition and relies solely on properties of the organic fraction that can be measured directly with available techniques. Thus, it has high potential for application to complex and ambient aerosol. It is not computationally demanding, and therefore also has potential for implementation to atmospheric models accounting for cloud microphysics.
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Mironova, I. A., and I. G. Usoskin. "Possible effect of extreme solar energetic particle events of September–October 1989 on polar stratospheric aerosols: a case study." Atmospheric Chemistry and Physics 13, no. 17 (September 2, 2013): 8543–50. http://dx.doi.org/10.5194/acp-13-8543-2013.
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Abstract. The main ionization source of the middle and low Earth's atmosphere is related to energetic particles coming from outer space. Usually it is ionization from cosmic rays that is always present in the atmosphere. But in a case of a very strong solar eruption, some solar energetic particles (SEPs) can reach middle/low atmosphere increasing the ionization rate up to some orders of magnitude at polar latitudes. We continue investigating such a special class of solar events and their possible applications for natural variations of the aerosol content. After the case study of the extreme SEP event of January 2005 and its possible effect upon polar stratospheric aerosols, here we analyze atmospheric applications of the sequence of several events that took place over autumn 1989. Using aerosol data obtained over polar regions from two satellites with space-borne optical instruments SAGE II and SAM II that were operating during September–October 1989, we found that an extreme major SEP event might have led to formation of new particles and/or growth of preexisting ultrafine particles in the polar stratospheric region. However, the effect of the additional ambient air ionization on the aerosol formation is minor, in comparison with temperature effect, and can take place only in the cold polar atmospheric conditions. The extra aerosol mass formed under the temperature effect allows attributing most of the changes to the "ion–aerosol clear sky mechanism".
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Snow-Kropla, E. J., J. R. Pierce, D. M. Westervelt, and W. Trivitayanurak. "Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties." Atmospheric Chemistry and Physics 11, no. 8 (April 29, 2011): 4001–13. http://dx.doi.org/10.5194/acp-11-4001-2011.
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Abstract. The flux of cosmic rays to the atmosphere has been reported to correlate with cloud and aerosol properties. One proposed mechanism for these correlations is the "ion-aerosol clear-air" mechanism where the cosmic rays modulate atmospheric ion concentrations, ion-induced nucleation of aerosols and cloud condensation nuclei (CCN) concentrations. We use a global chemical transport model with online aerosol microphysics to explore the dependence of CCN concentrations on the cosmic-ray flux. Expanding upon previous work, we test the sensitivity of the cosmic-ray/CCN connection to several uncertain parameters in the model including primary emissions, Secondary Organic Aerosol (SOA) condensation and charge-enhanced condensational growth. The sensitivity of CCN to cosmic rays increases when simulations are run with decreased primary emissions, but show location-dependent behavior from increased amounts of secondary organic aerosol and charge-enhanced growth. For all test cases, the change in the concentration of particles larger than 80 nm between solar minimum (high cosmic ray flux) and solar maximum (low cosmic ray flux) simulations is less than 0.2 %. The change in the total number of particles larger than 10 nm was larger, but always less than 1 %. The simulated change in the column-integrated Ångström exponent was negligible for all test cases. Additionally, we test the predicted aerosol sensitivity to week-long Forbush decreases of cosmic rays and find that the maximum change in aerosol properties for these cases is similar to steady-state aerosol differences between the solar maximum and solar minimum. These results provide evidence that the effect of cosmic rays on CCN and clouds through the ion-aerosol clear-sky mechanism is limited by dampening from aerosol processes.
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Suni, T., L. Sogacheva, J. Lauros, H. Hakola, J. Bäck, T. Kurtén, H. Cleugh, et al. "Cold oceans enhance terrestrial new-particle formation in near-coastal forests." Atmospheric Chemistry and Physics Discussions 9, no. 3 (June 11, 2009): 13093–122. http://dx.doi.org/10.5194/acpd-9-13093-2009.
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Abstract. The world's forests produce atmospheric aerosol by emitting volatile organic compounds (VOC) which, after being oxidized in the atmosphere, readily condense on the omnipresent nanometer-sized nuclei and grow them to climatically relevant sizes. The cooling effect of aerosols is the greatest uncertainty in current climate models and estimates of radiative forcing. Therefore, identifying the environmental factors influencing the biogenic formation of aerosols is crucial. We show that, in addition to local meteorological factors in the forest, the magnitude of evaporation from oceans hundreds of kilometers upwind can effectively suppress or enhance new-particle formation. Our findings indicate that, unlike warm waters, the cold polar oceans provide excellent clean and dry background air that enhances aerosol formation above near-coastal forests in Fennoscandia and South-East Australia.
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Trivitayanurak, W., and P. J. Adams. "Does the POA–SOA split matter for global CCN formation?" Atmospheric Chemistry and Physics 14, no. 2 (January 28, 2014): 995–1010. http://dx.doi.org/10.5194/acp-14-995-2014.
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Abstract. A model of carbonaceous aerosols has been implemented in the TwO-Moment Aerosol Sectional (TOMAS) microphysics module in the GEOS-Chem chemical transport model (CTM), a model driven by assimilated meteorology. Inclusion of carbonaceous emissions alongside pre-existing treatments of sulfate and sea-salt aerosols increases the number of emitted primary aerosol particles by a factor of 2.5 and raises annual-average global cloud condensation nuclei at 0.2% supersaturation (CCN(0.2%)) concentrations by a factor of two. Compared to the prior model without carbonaceous aerosols, this development improves the model prediction of condensation nuclei with dry diameter larger than 10 nm (CN10) number concentrations significantly from −45% to −7% bias when compared to long-term observations. Inclusion of carbonaceous particles also largely eliminates a tendency for the model to underpredict higher cloud condensation nuclei (CCN) concentrations. Similar to other carbonaceous models, the model underpredicts organic carbon (OC) and elemental carbon (EC) mass concentrations by a factor of 2 when compared to EMEP and IMPROVE observations. Because primary organic aerosol (POA) and secondary organic aerosol (SOA) affect aerosol number size distributions via different microphysical processes, we assess the sensitivity of CCN production, for a fixed source of organic aerosol (OA) mass, to the assumed POA–SOA split in the model. For a fixed OA budget, we found that CCN(0.2%) decreases nearly everywhere as the model changes from a world dominated by POA emissions to one dominated by SOA condensation. POA is about twice as effective per unit mass at CCN production compared to SOA. Changing from a 100% POA scenario to a 100% SOA scenario, CCN(0.2%) concentrations in the lowest model layer decrease by about 20%. In any scenario, carbonaceous aerosols contribute significantly to global CCN. The SOA–POA split has a significant effect on global CCN, and the microphysical implications of POA emissions versus SOA condensation appear to be at least as important as differences in chemical composition as expressed by the hygroscopicity of OA. These findings stress the need to better understand carbonaceous aerosols loadings, the global SOA budget, microphysical pathways of OA formation (emissions versus condensation) as well as chemical composition to improve climate modeling.
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Lu, Dawei, Jihua Tan, Xuezhi Yang, Xu Sun, Qian Liu, and Guibin Jiang. "Unraveling the role of silicon in atmospheric aerosol secondary formation: a new conservative tracer for aerosol chemistry." Atmospheric Chemistry and Physics 19, no. 5 (March 5, 2019): 2861–70. http://dx.doi.org/10.5194/acp-19-2861-2019.
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Abstract. Aerosol particles are ubiquitous in the atmosphere and affect the quality of human life through their climatic and health effects. The formation and growth of aerosol particles involve extremely complex reactions and processes. Due to limited research tools, the sources and chemistry of aerosols are still not fully understood, and until now have normally been investigated by using chemical species of secondary aerosols (e.g., NH4+, NO3-, SO42-, SOC) as tracers. Here we investigated the role of silicon (Si), an ubiquitous but relatively inert element, during the secondary aerosol formation process. We analyzed the correlation of Si in airborne fine particles (PM2.5) collected in Beijing – a typical pollution region – with the secondary chemical species and secondary particle precursors (e.g., SO2 and NOx). The total mass of Si in PM2.5 was found to be uncorrelated with the secondary aerosol formation process, which suggested that Si is a new conservative tracer for the amount of primary materials in PM2.5 and can be used to estimate the relative amount of secondary and primary compounds in PM2.5. This finding enables the accurate estimation of secondary aerosol contribution to PM2.5 by using Si as a single tracer rather than the commonly used multiple chemical tracers. In addition, we show that the correlation analysis of secondary aerosols with the Si isotopic composition of PM2.5 can further reveal the sources of the precursors of secondary aerosols. Therefore, Si may provide a new tool for aerosol chemistry studies.
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Hohaus, T., D. Trimborn, A. Kiendler-Scharr, I. Gensch, W. Laumer, B. Kammer, S. Andres, et al. "A new aerosol collector for on-line analysis of particulate organic matter: the Aerosol Collection Module (ACM)." Atmospheric Measurement Techniques Discussions 3, no. 2 (March 31, 2010): 1361–98. http://dx.doi.org/10.5194/amtd-3-1361-2010.
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Abstract. In many environments organic matter significantly contributes to the composition of atmospheric aerosol particles influencing its properties. Detailed chemical characterization of ambient aerosols is critical in order to understand the formation process, composition, and properties of aerosols in the atmosphere. However, current analytical methods are far from full speciation of organic aerosols and often require long sampling times. Offline methods are also subjected to artifacts during aerosol collection and storage. In the present work a new technique for quasi-online compound specific measurements of organic aerosol particles was developed. The Aerosol Collection Module (ACM) is designed to sample, collect and transfer gasified atmospheric aerosol particles. The system focuses particles into a beam which is directed to a cooled sampling surface. The sampling takes places in a high vacuum environment where the gas phase from the sample volume is removed. After collection the particle sample is evaporated from the collection surface through heating and transferred to a detector. For laboratory characterization the ACM was interfaced with a Gas Chromatograph Mass Spectrometer system (GC-MS). The particle collection efficiency, gas phase transfer efficiency, and linearity of the ACM-GC-MS were determined using laboratory generated octadecane aerosols. The ACM-GC-MS is linear over the investigated mass range of 10 to 100 ng and a recovery rate of 100% was found for octadecane particles. The ACM-GC-MS was applied to investigate secondary organic aerosol (SOA) formed from β-pinene oxidation. Nopinone, myrtanal, myrtenol, 1-hydroxynopinone, 3-oxonopinone, 3,7-dihydroxynopinone, and bicyclo[3,1,1]hept-3-ene-2-one were found as products in the SOA. The ACM results are compared to quartz filter samples taken in parallel to the ACM measurements. First measurements of ambient atmospheric aerosols are presented.
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LAAKSONEN, ARI. "NUCLEATION THEORIES AND ATMOSPHERIC AEROSOL FORMATION." Journal of Aerosol Science 32 (September 2001): 323–24. http://dx.doi.org/10.1016/s0021-8502(21)00153-1.
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KERMINEN, V.-M., T. ANTTILA, K. LEHTINEN, and M. KULMALA. "A PARAMETERIZATION FOR ATMOSPHERIC AEROSOL FORMATION." Journal of Aerosol Science 35 (July 2004): S1221—S1222. http://dx.doi.org/10.1016/s0021-8502(19)30335-0.
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Beaver, M. R., M. J. Elrod, R. M. Garland, and M. A. Tolbert. "Ice nucleation in sulfuric acid/organic aerosols: implications for cirrus cloud formation." Atmospheric Chemistry and Physics 6, no. 11 (August 4, 2006): 3231–42. http://dx.doi.org/10.5194/acp-6-3231-2006.
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Abstract. Using an aerosol flow tube apparatus, we have studied the effects of aliphatic aldehydes (C3 to C10) and ketones (C3 and C9) on ice nucleation in sulfuric acid aerosols. Mixed aerosols were prepared by combining an organic vapor flow with a flow of sulfuric acid aerosols over a small mixing time (~60 s) at room temperature. No acid-catalyzed reactions were observed under these conditions, and physical uptake was responsible for the organic content of the sulfuric acid aerosols. In these experiments, aerosol organic content, determined by a Mie scattering analysis, was found to vary with the partial pressure of organic, the flow tube temperature, and the identity of the organic compound. The physical properties of the organic compounds (primarily the solubility and melting point) were found to play a dominant role in determining the inferred mode of nucleation (homogenous or heterogeneous) and the specific freezing temperatures observed. Overall, very soluble, low-melting organics, such as acetone and propanal, caused a decrease in aerosol ice nucleation temperatures when compared with aqueous sulfuric acid aerosol. In contrast, sulfuric acid particles exposed to organic compounds of eight carbons and greater, of much lower solubility and higher melting temperatures, nucleate ice at temperatures above aqueous sulfuric acid aerosols. Organic compounds of intermediate carbon chain length, C4-C7, (of intermediate solubility and melting temperatures) nucleated ice at the same temperature as aqueous sulfuric acid aerosols. Interpretations and implications of these results for cirrus cloud formation are discussed.
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Ortega, I. K., T. Suni, M. Boy, T. Grönholm, H. E. Manninen, T. Nieminen, M. Ehn, et al. "New insights into nocturnal nucleation." Atmospheric Chemistry and Physics 12, no. 9 (May 15, 2012): 4297–312. http://dx.doi.org/10.5194/acp-12-4297-2012.
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Abstract. Formation of new aerosol particles by nucleation and growth is a significant source of aerosols in the atmosphere. New particle formation events usually take place during daytime, but in some locations they have been observed also at night. In the present study we have combined chamber experiments, quantum chemical calculations and aerosol dynamics models to study nocturnal new particle formation. All our approaches demonstrate, in a consistent manner, that the oxidation products of monoterpenes play an important role in nocturnal nucleation events. By varying the conditions in our chamber experiments, we were able to reproduce the very different types of nocturnal events observed earlier in the atmosphere. The exact strength, duration and shape of the events appears to be sensitive to the type and concentration of reacting monoterpenes, as well as the extent to which the monoterpenes are exposed to ozone and potentially other atmospheric oxidants.
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Gassó, Santiago, and Kirk D. Knobelspiesse. "Circular polarization in atmospheric aerosols." Atmospheric Chemistry and Physics 22, no. 20 (October 20, 2022): 13581–605. http://dx.doi.org/10.5194/acp-22-13581-2022.
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Abstract. Recent technological advances have demonstrated the feasibility of deploying spaceborne optical detectors with full polarimetric capabilities. The measurement of all four Stokes coefficients opens significant new opportunities for atmospheric aerosol studies and applications. While considerable amounts of attention have been dedicated to sensors with sensitivity to the total intensity and linear polarization (represented by Stokes coefficients I, U, Q), there has been less attention to the additional information brought by measuring circular polarization (coefficient V). This report fills this gap in knowledge by providing an overview of aerosol sources of circular polarization in the atmosphere and discusses possible remote sensing signatures. In this paper, circularly polarized radiation that results from the interaction of incident unpolarized radiation is considered in three physical settings: optical activity originating in biogenic aerosols, alignment of non-spherical particles in the presence of electrical fields (such as dust, smoke, and volcanic ash), and aerosol multiple scattering effects. Observational and theoretical evidence of, and the settings and conditions for, non-zero aerosol circular polarization generated from incident unpolarized radiation are here gathered and discussed. In addition, novel radiative transfer simulations are shown to illustrate notable spectral and other features where circular polarization may provide additional information that is possibly independent from total intensity and linear polarization-only observations. Current techniques for the detection of aerosol composition (also referred as aerosol type) from space provide limited information. Remote identification of aerosols such as smoke, volcanic ash, and dust particles can only be accomplished with some degree of confidence for moderate to high concentrations. When the same aerosols are found at lower concentrations (but still high enough to be of importance for air quality and cloud formation), these methods often produce ambiguous results. The circular polarization of aerosols is rarely utilized, and we explore its value for improved determination aerosol composition. This study is presented as an overview with a goal to provide a new perspective on an overlooked optical property and to trigger interest in further exploration of this subject.
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Lewellen, David C. "A Large-Eddy Simulation Study of Contrail Ice Number Formation." Journal of the Atmospheric Sciences 77, no. 7 (July 1, 2020): 2585–604. http://dx.doi.org/10.1175/jas-d-19-0322.1.
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AbstractIce crystal number is a critical ingredient in the potential climate impact of persistent contrails and contrail-induced cirrus. We perform an extensive set of large-eddy simulations (LES) of ice nucleation and growth within aircraft exhaust jets with an emphasis on assessing the importance of detailed plume mixing on the effective ice-number emission index (EIiceno) produced for different conditions. Parameter variations considered include ambient temperature, pressure, and humidity; initial aerosol origin (exhaust or ambient), number, and properties; and aircraft engine size. The LES are performed in a temporal representation with binned microphysics including the basics of activation of underlying aerosol, droplet growth, and freezing. We find that a box-model approach reproduces EIiceno from LES well for sufficiently low aerosol numbers or when crystal production is predominantly on ambient aerosol. For larger exhaust aerosol number the box model generally overestimates EIiceno and can underestimate the fraction from ultrafine aerosol. The effects of different parameters on EIiceno can largely be understood with simpler analytic models that are formulated in low and high aerosol-number limits. The simulations highlight the potential importance of “cold” contrails, ambient ultrafine aerosols, crystal loss due to competition between different-sized crystals, and limitations on reducing EIiceno. We find EIiceno insensitive to engine size for lower aerosol numbers, but decreasing with increasing engine size for higher aerosol numbers. Temporal versus spatial representations for jet LES are compared in an appendix.
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Riipinen, I., J. R. Pierce, T. Yli-Juuti, T. Nieminen, S. Häkkinen, M. Ehn, H. Junninen, et al. "Organic condensation – a vital link connecting aerosol formation to climate forcing." Atmospheric Chemistry and Physics Discussions 11, no. 1 (January 6, 2011): 387–423. http://dx.doi.org/10.5194/acpd-11-387-2011.
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Abstract. Atmospheric aerosol particles influence global climate as well as impair air quality through their effects on atmospheric visibility and human health. Ultrafine (<100 nm) particles often dominate aerosol numbers, and nucleation of atmospheric vapors is an important source of these particles. To have climatic relevance, however, the freshly-nucleated particles need to grow in size. We combine observations from two continental sites (Egbert, Canada and Hyytiälä, Finland) to show that condensation of organic vapors is a crucial factor governing the lifetimes and climatic importance of the smallest atmospheric particles. We demonstrate that state-of-the-science organic gas-particle partitioning models fail to reproduce the observations, and propose a modeling approach that is consistent with the measurements. We demonstrate the large sensitivity of climatic forcing of atmospheric aerosols to these interactions between organic vapors and the smallest atmospheric nanoparticles – highlighting the need for representing this process in global climate models.
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Lampilahti, Janne, Katri Leino, Antti Manninen, Pyry Poutanen, Anna Franck, Maija Peltola, Paula Hietala, et al. "Aerosol particle formation in the upper residual layer." Atmospheric Chemistry and Physics 21, no. 10 (May 25, 2021): 7901–15. http://dx.doi.org/10.5194/acp-21-7901-2021.
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Abstract. According to current estimates, atmospheric new particle formation (NPF) produces a large fraction of aerosol particles and cloud condensation nuclei in the Earth's atmosphere, which have implications for health and climate. Despite recent advances, atmospheric NPF is still insufficiently understood in the lower troposphere, especially above the mixed layer (ML). This paper presents new results from co-located airborne and ground-based measurements in a boreal forest environment, showing that many NPF events (∼42 %) appear to start in the topmost part of the residual layer (RL). The freshly formed particles may be entrained into the growing mixed layer (ML) where they continue to grow in size, similar to the aerosol particles formed within the ML. The results suggest that in the boreal forest environment, NPF in the upper RL has an important contribution to the aerosol load in the boundary layer (BL).
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Hatzianastassiou, N., C. Matsoukas, A. Fotiadi, E. Drakakis, P. W. Stackhouse, P. Koepke, K. G. Pavlakis, D. Hatzidimitriou, and I. Vardavas. "Modelling the direct effect of aerosols in the solar near-infrared on a planetary scale." Atmospheric Chemistry and Physics Discussions 6, no. 5 (September 25, 2006): 9151–85. http://dx.doi.org/10.5194/acpd-6-9151-2006.
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Abstract. We used a spectral radiative transfer model to compute the direct radiative effect (DRE) of natural plus anthropogenic aerosols in the solar near-infrared (IR), between 0.85–10 µm, namely, their effect on the outgoing near-IR radiation at the top of atmosphere (TOA, ΔFTOA), on the atmospheric absorption of near-IR radiation (ΔFatmab) and on the surface downward and absorbed near-IR radiation (ΔFsurf, and ΔFsurfnet, respectively). The computations were performed on a global scale (over land and ocean) under all-sky conditions, using spectral aerosol optical properties taken from the Global Aerosol Data Set (GADS) supplemented by realistic data for the rest of surface and atmospheric parameters. The computed aerosol DRE, averaged over the 12-year period 1984–1995 for January and July, shows that aerosols produce a planetary cooling by increasing the scattered near-IR radiation back to space (by up to 6 Wm−2), they warm the atmosphere (by up to 7 Wm−2) and cool the surface (by up to 12 Wm−2). However, they can also slightly warm the Earth-atmosphere system or cool the atmosphere (by less than 1 Wm−2) over limited areas. The magnitude of the near-IR aerosol DRE is smaller than that of the combined ultraviolet (UV) and visible DRE, but it is still energetically important, since it contributes to the total shortwave (SW) DRE by 22–31%. On a global mean basis, the DREs ΔFTOA, ΔFatmab, ΔFsurf, and ΔFsurfnet are equal to about 0.48, 0.37, −1.03 and −0.85 Wm−2, i.e. their magnitude is similar to that of climate forcing associated with increasing concentrations of greenhouse gases. The aerosol induced near-IR surface cooling combined with the atmospheric warming, affects the thermal dynamics of the Earth-atmosphere system, by increasing the atmospheric stability, decreasing thus cloud formation, and precipitation, especially over desertification threatened regions such as the Mediterranean basin. This, together with the fact that the sign of near-IR aerosol DRE is sometimes opposite to that of UV-visible DRE, demonstrates the importance of performing detailed spectral computations to provide estimates of the climatic role of aerosols for the Earth-atmosphere system.
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Cao, Li-Ming, Xiao-Feng Huang, Yuan-Yuan Li, Min Hu, and Ling-Yan He. "Volatility measurement of atmospheric submicron aerosols in an urban atmosphere in southern China." Atmospheric Chemistry and Physics 18, no. 3 (February 6, 2018): 1729–43. http://dx.doi.org/10.5194/acp-18-1729-2018.
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Abstract. Aerosol pollution has been a very serious environmental problem in China for many years. The volatility of aerosols can affect the distribution of compounds in the gas and aerosol phases, the atmospheric fates of the corresponding components, and the measurement of the concentration of aerosols. Compared to the characterization of chemical composition, few studies have focused on the volatility of aerosols in China. In this study, a thermodenuder aerosol mass spectrometer (TD-AMS) system was deployed to study the volatility of non-refractory submicron particulate matter (PM1) species during winter in Shenzhen. To our knowledge, this paper is the first report of the volatilities of aerosol chemical components based on a TD-AMS system in China. The average PM1 mass concentration during the experiment was 42.7±20.1 µg m−3, with organic aerosol (OA) being the most abundant component (43.2 % of the total mass). The volatility of chemical species measured by the AMS varied, with nitrate showing the highest volatility, with a mass fraction remaining (MFR) of 0.57 at 50 ∘C. Organics showed semi-volatile characteristics (the MFR was 0.88 at 50 ∘C), and the volatility had a relatively linear correlation with the TD temperature (from the ambient temperature to 200 ∘C), with an evaporation rate of 0.45 %∘C-1. Five subtypes of OA were resolved from total OA using positive matrix factorization (PMF) for data obtained under both ambient temperature and high temperatures through the TD, including a hydrocarbon-like OA (HOA, accounting for 13.5 %), a cooking OA (COA, 20.6 %), a biomass-burning OA (BBOA, 8.9 %), and two oxygenated OAs (OOAs): a less-oxidized OOA (LO-OOA, 39.1 %) and a more-oxidized OOA (MO-OOA, 17.9 %). Different OA factors presented different volatilities, and the volatility sequence of the OA factors at 50 ∘C was HOA (MFR of 0.56) > LO-OOA (0.70) > COA (0.85) ≈ BBOA (0.87) > MO-OOA (0.99), which was not completely consistent with the sequence of their O ∕ C ratios. The high volatility of HOA implied that it had a high potential to be oxidized to secondary species in the gas phase. The aerosol volatility measurement results in this study provide useful parameters for the modeling work of aerosol evolution in China and are also helpful in understanding the formation mechanisms of secondary aerosols.
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Liu, Lixia, Yafang Cheng, Siwen Wang, Chao Wei, Mira L. Pöhlker, Christopher Pöhlker, Paulo Artaxo, et al. "Impact of biomass burning aerosols on radiation, clouds, and precipitation over the Amazon: relative importance of aerosol–cloud and aerosol–radiation interactions." Atmospheric Chemistry and Physics 20, no. 21 (November 10, 2020): 13283–301. http://dx.doi.org/10.5194/acp-20-13283-2020.
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Abstract. Biomass burning (BB) aerosols can influence regional and global climate through interactions with radiation, clouds, and precipitation. Here, we investigate the impact of BB aerosols on the energy balance and hydrological cycle over the Amazon Basin during the dry season. We performed simulations with a fully coupled meteorology–chemistry model, the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), for a range of different BB emission scenarios to explore and characterize nonlinear effects and individual contributions from aerosol–radiation interactions (ARIs) and aerosol–cloud interactions (ACIs). The ARIs of BB aerosols tend to suppress low-level liquid clouds by local warming and increased evaporation and to facilitate the formation of high-level ice clouds by enhancing updrafts and condensation at high altitudes. In contrast, the ACIs of BB aerosol particles tend to enhance the formation and lifetime of low-level liquid clouds by providing more cloud condensation nuclei (CCN) and to suppress the formation of high-level ice clouds by reducing updrafts and condensable water vapor at high altitudes (>8 km). For scenarios representing the lower and upper limits of BB emission estimates for recent years (2002–2016), we obtained total regional BB aerosol radiative forcings of −0.2 and 1.5 W m−2, respectively, showing that the influence of BB aerosols on the regional energy balance can range from modest cooling to strong warming. We find that ACIs dominate at low BB emission rates and low aerosol optical depth (AOD), leading to an increased cloud liquid water path (LWP) and negative radiative forcing, whereas ARIs dominate at high BB emission rates and high AOD, leading to a reduction of LWP and positive radiative forcing. In all scenarios, BB aerosols led to a decrease in the frequency of occurrence and rate of precipitation, caused primarily by ACI effects at low aerosol loading and by ARI effects at high aerosol loading. The dependence of precipitation reduction on BB aerosol loading is greater in a strong convective regime than under weakly convective conditions. Overall, our results show that ACIs tend to saturate at high aerosol loading, whereas the strength of ARIs continues to increase and plays a more important role in highly polluted episodes and regions. This should hold not only for BB aerosols over the Amazon, but also for other light-absorbing aerosols such as fossil fuel combustion aerosols in industrialized and densely populated areas. The importance of ARIs at high aerosol loading highlights the need for accurately characterizing aerosol optical properties in the investigation of aerosol effects on clouds, precipitation, and climate.
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Kulmala, M., T. Suni, K. E. J. Lehtinen, M. Dal Maso, M. Boy, A. Reissell, Ü. Rannik, et al. "A new feedback mechanism linking forests, aerosols, and climate." Atmospheric Chemistry and Physics 4, no. 2 (March 30, 2004): 557–62. http://dx.doi.org/10.5194/acp-4-557-2004.
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Abstract. The possible connections between the carbon balance of ecosystems and aerosol-cloud-climate interactions play a significant role in climate change studies. Carbon dioxide is a greenhouse gas, whereas the net effect of atmospheric aerosols is to cool the climate. Here, we investigated the connection between forest-atmosphere carbon exchange and aerosol dynamics in the continental boundary layer by means of multiannual data sets of particle formation and growth rates, of CO2 fluxes, and of monoterpene concentrations in a Scots pine forest in southern Finland. We suggest a new, interesting link and a potentially important feedback among forest ecosystem functioning, aerosols, and climate: Considering that globally increasing temperatures and CO2 fertilization are likely to lead to increased photosynthesis and forest growth, an increase in forest biomass would increase emissions of non-methane biogenic volatile organic compounds and thereby enhance organic aerosol production. This feedback mechanism couples the climate effect of CO2 with that of aerosols in a novel way.
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Chan, C. H., A. Y. S. Cheng, and A. Viseu. "A simplified empirical method for determination of aerosol hygroscopicity and composition." Atmospheric Chemistry and Physics Discussions 10, no. 10 (October 12, 2010): 23627–56. http://dx.doi.org/10.5194/acpd-10-23627-2010.
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Abstract. Atmospheric aerosols have substantial influence on the Earth's radiation budget, visibility, cloud formation and precipitation. The aerosol hygroscopicity and the composition of aerosols are of vital importance for solar radiation budget calculation, cloud formation mechanism, and measurement of aerosol spatiotemporal distribution through remote sensing, such as Lidar, MODIS and sun/star photometer. In this paper, hourly averaged records of humidity, visibility and aerosol concentration, conducted in Macao, P.R.C. from 1 February 2006 to 31 December 2008 (LT), are used to estimate aerosol hygroscopicity and composition with a simplified empirical method. The result of monthly variation of aerosol hygroscopicity indicates the important role of aerosol composition on optical properties, which is in agreement with the previous study. This aerosol composition pattern is also consistent with the Asiatic Monsoon pattern and vicinity, such as Hong Kong. The monthly variation of aerosol hygroscopicity and composition also shows the necessity to consider such a factor for the aerosols monitoring by remote system and aerosols forcing simulated by climate model.
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Kim, Youngseob, Karine Sartelet, and Florian Couvidat. "Modeling the effect of non-ideality, dynamic mass transfer and viscosity on SOA formation in a 3-D air quality model." Atmospheric Chemistry and Physics 19, no. 2 (January 31, 2019): 1241–61. http://dx.doi.org/10.5194/acp-19-1241-2019.
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Abstract. In this study, assumptions (ideality and thermodynamic equilibrium) commonly made in three-dimensional (3-D) air quality models were reconsidered to evaluate their impacts on secondary organic aerosol (SOA) formation over Europe. To investigate the effects of non-ideality, dynamic mass transfer and aerosol viscosity on the SOA formation, the Secondary Organic Aerosol Processor (SOAP) model was implemented in the 3-D air quality model Polyphemus. This study presents the first 3-D modeling simulation which describes the impact of aerosol viscosity on the SOA formation. The model uses either the equilibrium approach or the dynamic approach with a method specially designed for 3-D air quality models to efficiently solve particle-phase diffusion when particles are viscous. Sensitivity simulations using two organic aerosol models implemented in Polyphemus to represent mass transfer between gas and particle phases show that the computation of the absorbing aerosol mass strongly influences the SOA formation. In particular, taking into account the concentrations of inorganic aerosols and hydrophilic organic aerosols in the absorbing mass of the aqueous phase increases the average SOA concentration by 5 % and 6 %, respectively. However, inorganic aerosols influence the SOA formation not only because they constitute an absorbing mass for hydrophilic SOA, but also because they interact with organic compounds. Non-ideality (short-, medium- and long-range interactions) was found to influence SOA concentrations by about 30 %. Concerning the dynamic mass transfer for the SOA formation, if the viscosity of SOA is not taken into account and if ideality of aerosols is assumed, the dynamic approach is found to give generally similar results to the equilibrium approach (indicating that equilibrium is an efficient hypothesis for inviscid and ideal aerosols). However, when a non-ideal aerosol is assumed, taking into account the dynamic mass transfer leads to a decrease of concentrations of the hydrophilic compounds (compared to equilibrium). This decrease is due to differences in the values of activity coefficients, which are different between values computed for bulk aerosols and those for each size section. This result indicates the importance of non-ideality on the dynamic evolution of SOA. For viscous aerosols, assuming a highly viscous organic phase leads to an increase in SOA concentrations during daytime (by preventing the evaporation of the most volatile organic compounds). The partitioning of nonvolatile compounds is not affected by viscosity, but the aging of more volatile compounds (that leads to the formation of the less volatile compounds) slows down as the evaporation of those compounds is stopped due to the viscosity of the particle. These results imply that aerosol concentrations may deviate significantly from equilibrium as the gas–particle partitioning could be higher than predicted by equilibrium. Furthermore, although a compound evaporates in the simulation using the equilibrium approach, the same compound can condense in the simulation using the dynamic approach if the particles are viscous. The results of this study emphasize the need for 3-D air quality models to take into account the effect of non-ideality on SOA formation and the effect of aerosol viscosity for the more volatile fraction of semi-volatile organic compounds.
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Wang, Jiandong, Jia Xing, Shuxiao Wang, Rohit Mathur, Jiaping Wang, Yuqiang Zhang, Chao Liu, et al. "The pathway of impacts of aerosol direct effects on secondary inorganic aerosol formation." Atmospheric Chemistry and Physics 22, no. 8 (April 20, 2022): 5147–56. http://dx.doi.org/10.5194/acp-22-5147-2022.
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Abstract. Airborne aerosols reduce surface solar radiation through light scattering and absorption (aerosol direct effects, ADEs), influence regional meteorology, and further affect atmospheric chemical reactions and aerosol concentrations. The inhibition of turbulence and the strengthened atmospheric stability induced by ADEs increases surface primary aerosol concentration, but the pathway of ADE impacts on secondary aerosol is still unclear. In this study, the online coupled meteorological and chemistry model (WRF–CMAQ; Weather Research and Forecasting–Community Multiscale Air Quality) with integrated process analysis was applied to explore how ADEs affect secondary aerosol formation through changes in atmospheric dynamics and photolysis processes. The meteorological condition and air quality in the Jing-Jin-Ji area (denoted JJJ, including Beijing, Tianjin, and Hebei Province in China) in January and July 2013 were simulated to represent winter and summer conditions, respectively. Our results show that ADEs through the photolysis pathway inhibit sulfate formation during winter in the JJJ region and promote sulfate formation in July. The differences are attributed to the alteration of effective actinic flux affected by single-scattering albedo (SSA). ADEs through the dynamics pathway act as an equally or even more important route compared with the photolysis pathway in affecting secondary aerosol concentration in both summer and winter. ADEs through dynamics traps formed sulfate within the planetary boundary layer (PBL) which increases sulfate concentration in winter. Meanwhile, the impact of ADEs through dynamics is mainly reflected in the increase of gaseous-precursor concentrations within the PBL which enhances secondary aerosol formation in summer. For nitrate, reduced upward transport of precursors restrains the formation at high altitude and eventually lowers the nitrate concentration within the PBL in winter, while such weakened vertical transport of precursors increases nitrate concentration within the PBL in summer, since nitrate is mainly formed near the surface ground.
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Bhawar, R. L., and P. C. S. Devara. "Study of successive contrasting monsoons (2001–2002) in terms of aerosol variability over a tropical station Pune, India." Atmospheric Chemistry and Physics 10, no. 1 (January 5, 2010): 29–37. http://dx.doi.org/10.5194/acp-10-29-2010.
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Abstract. The present study suggests that aerosols play a major role in cloud formation and affect significantly the precipitation over a regional scale. The study reveals that there is a high variability of aerosol index during a bad monsoon year 2002, indicating an extension of cycle to more than 100 days from a normal 50 day cycle of absorbing and non-absorbing aerosols over a tropical urban station Pune. Pre-monsoon of 2002 shows a high loading of coarse-mode aerosols (absorbing dust aerosols) which indicate vertical and horizontal temperature variations in turn affecting the seasonal rainfall at a regional scale. Cloud formation highly depends on aerosol concentration, but the activation process is not monotonic. The surface meteorological features help to initiate the cloud process. The surface temperatures were high during the pre-monsoon of 2002 leading to increase of aerosol optical depth as compared to 2001. The effect of surface wind speed, though, complicated to understand, results in low values in 2002 with high aerosol optical depth and vice-versa in 2001.
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Woo, J. L., and V. F. McNeill. "simpleGAMMA – a reduced model of secondary organic aerosol formation in the aqueous aerosol phase (aaSOA)." Geoscientific Model Development Discussions 8, no. 1 (January 22, 2015): 463–82. http://dx.doi.org/10.5194/gmdd-8-463-2015.
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Abstract. There is increasing evidence that the uptake and aqueous processing of water-soluble volatile organic compounds (VOCs) by wet aerosols or cloud droplets is an important source of secondary organic aerosol (SOA). We recently developed GAMMA (Gas–Aerosol Model for Mechanism Analysis), a zero-dimensional kinetic model that couples gas-phase and detailed aqueous-phase atmospheric chemistry for speciated prediction of SOA and organosulfate formation in cloudwater or aqueous aerosols. Results from GAMMA simulations of SOA formation in aerosol water (McNeill et al., 2012) indicate that it is dominated by two pathways: isoprene epoxydiol (IEPOX) uptake followed by ring-opening chemistry (under low-NOx conditions) and glyoxal uptake. This suggested that it is possible to model the majority of aqueous aerosol phase SOA mass using a highly simplified reaction scheme. We have therefore developed a reduced version of GAMMA, simpleGAMMA. Close agreement in predicted aaSOA mass is observed between simpleGAMMA and GAMMA under all conditions tested (between pH 1–4 and RH 40–80%) after 12 h of simulation. simpleGAMMA is computationally efficient and suitable for coupling with larger-scale atmospheric chemistry models.