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Sökning: WFRF:(Tunved Peter)

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1.
  • Ahn, Seo H., et al. (författare)
  • Relationship between cloud condensation nuclei (CCN) concentration and aerosol optical depth in the Arctic region
  • 2021
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 267
  • Tidskriftsartikel (refereegranskat)abstract
    • To determine the direct and indirect effects of aerosols on climate, it is important to know the spatial and temporal variations in cloud condensation nuclei (CCN) concentrations. Although many types of CCN measurements are available, extensive CCN measurements are challenging because of the complexity and high operating cost, especially in remote areas. As aerosol optical depth (AOD) can be readily observed by remote sensing, many attempts have been made to estimate CCN concentrations from AOD. In this study, the CCN-AOD relationship is parameterized based on CCN ground measurements from the Zeppelin Observatory (78.91 degrees N, 11.89 degrees E, 474 m asl) in the Arctic region. The AOD measurements were obtained from the Ny-Alesund site (78.923 degrees N, 11.928 degrees E) and Modern-Era Retrospective Analysis for Research and Applications, Version 2 reanalysis. Our results show a CCN-AOD correlation with a coefficient of determination R-2 of 0.59. Three additional estimation models for CCN were presented based on the following data: (i) in situ aerosol chemical composition, (ii) in situ aerosol optical properties, and (iii) chemical composition of AOD obtained from reanalysis data. The results from the model using in situ aerosol optical properties reproduced the observed CCN concentration most efficiently, suggesting that the contribution of BC to CCN concentration should be considered along with that of sulfate.
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2.
  • Artaxo, Paulo, et al. (författare)
  • Tropical and Boreal Forest – Atmosphere Interactions : A Review
  • 2022
  • Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 74:1, s. 24-163
  • Forskningsöversikt (refereegranskat)abstract
    • This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiäla in Finland. The review is complemented by short-term observations from networks and large experiments.The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction.Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink.It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.
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3.
  • Asmi, A., et al. (författare)
  • Number size distributions and seasonality of submicron particles in = rope 2008-2009
  • 2011
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:11, s. 5505-5538
  • Tidskriftsartikel (refereegranskat)abstract
    • Two years of harmonized aerosol number size distribution data from 24 = ropean field monitoring sites have been analysed. The results give a = mprehensive overview of the European near surface aerosol particle = mber concentrations and number size distributions between 30 and 500 = of dry particle diameter. Spatial and temporal distribution of = rosols in the particle sizes most important for climate applications = e presented. We also analyse the annual, weekly and diurnal cycles of = e aerosol number concentrations, provide log-normal fitting parameters = r median number size distributions, and give guidance notes for data = ers. Emphasis is placed on the usability of results within the aerosol = delling community.
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4.
  • Backman, John, et al. (författare)
  • On Aethalometer measurement uncertainties and an instrument correction factor for the Arctic
  • 2017
  • Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 10:12, s. 5039-5062
  • Tidskriftsartikel (refereegranskat)abstract
    • Several types of filter-based instruments are used to estimate aerosol light absorption coefficients. Two significant results are presented based on Aethalometer measurements at six Arctic stations from 2012 to 2014. First, an alternative method of post-processing the Aethalometer data is presented, which reduces measurement noise and lowers the detection limit of the instrument more effectively than box-car averaging. The biggest benefit of this approach can be achieved if instrument drift is minimised. Moreover, by using an attenuation threshold criterion for data post-processing, the relative uncertainty from the electronic noise of the instrument is kept constant. This approach results in a time series with a variable collection time (Delta t) but with a constant relative uncertainty with regard to electronic noise in the instrument. An additional advantage of this method is that the detection limit of the instrument will be lowered at small aerosol concentrations at the expense of temporal resolution, whereas there is little to no loss in temporal resolution at high aerosol concentrations (>2.1-6.7Mm(-1) as measured by the Aethalometers). At high aerosol concentrations, minimising the detection limit of the instrument is less critical. Additionally, utilising co-located filter-based absorption photometers, a correction factor is presented for the Arctic that can be used in Aethalometer corrections available in literature. The correction factor of 3.45 was calculated for low-elevation Arctic stations. This correction factor harmonises Aethalometer attenuation coefficients with light absorption coefficients as measured by the co-located light absorption photometers. Using one correction factor for Arctic Aethalometers has the advantage that measurements between stations become more inter-comparable.
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5.
  • Beddows, D. C. S., et al. (författare)
  • Variations in tropospheric submicron particle size distributions across the European continent 2008-2009
  • 2014
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:8, s. 4327-4348
  • Tidskriftsartikel (refereegranskat)abstract
    • Cluster analysis of particle number size distributions from background sites across Europe is presented. This generated a total of nine clusters of particle size distributions which could be further combined into two main groups, namely: a south-to-north category (four clusters) and a west-to-east category (five clusters). The first group was identified as most frequently being detected inside and around northern Germany and neighbouring countries, showing clear evidence of local afternoon nucleation and growth events that could be linked to movement of air masses from south to north arriving ultimately at the Arctic contributing to Arctic haze. The second group of particle size spectra proved to have narrower size distributions and collectively showed a dependence of modal diameter upon the longitude of the site (west to east) at which they were most frequently detected. These clusters indicated regional nucleation (at the coastal sites) growing to larger modes further inland. The apparent growth rate of the modal diameter was around 0.6-0.9 nm h(-1). Four specific air mass back-trajectories were successively taken as case studies to examine in real time the evolution of aerosol size distributions across Europe. While aerosol growth processes can be observed as aerosol traverses Europe, the processes are often obscured by the addition of aerosol by emissions en route. This study revealed that some of the 24 stations exhibit more complex behaviour than others, especially when impacted by local sources or a variety of different air masses. Overall, the aerosol size distribution clustering analysis greatly simplifies the complex data set and allows a description of aerosol aging processes, which reflects the longer-term average development of particle number size distributions as air masses advect across Europe.
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6.
  • Bisht, D. S., et al. (författare)
  • Tethered balloon-born and ground-based measurements. of black carbon and particulate profiles within the lower troposphere during the foggy period in Delhi, India
  • 2016
  • Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 573, s. 894-905
  • Tidskriftsartikel (refereegranskat)abstract
    • The ground and vertical profiles of particulate matter (PM) were mapped as part of a pilot study using a Tethered balloon within the lower troposphere (1000 m) during the foggy episodes in the winter season of 2015-16 in New Delhi, India. Measurements of black carbon (BC) aerosol and PM <2.5 and 10 mu m (PM2.5 &PM-10 respectively) concentrations and their associated particulate optical properties along with meteorological parameters were made. The mean concentrations of PM2.5, PM10, BC370 (nm), and BC880 nm were observed to be 146.8 +/- 42.1, 245.4 +/- 65.4, 30.3 +/- 122, and 24.1 +/- 103 mu g m(-3), respectively. The mean value of PM2.5 was similar to 12 times higher than the annual US-EPA air quality standard. The fraction of BC in PM2.5 that contributed to absorption in the shorter visible wavelengths (BC370 nm) was-21%. Compared to clear days, the ground level mass concentrations of PM2.5 and BC370 nm particles were substantially increased (59% and 24%, respectively) during the foggy episode. The aerosol light extinction coefficient (sigma(ext)) value was much higher (mean: 610 Mm(-1)) during the lower visibility (foggy) condition. Higher concentrations of PM2.5 (89 mu g m(-3)) and longer visible wavelength absorbing BC880 am (25.7 mu g m(-3)) particles were observed up to 200 m. The BC880 nm and PM2.5 aerosol concentrations near boundary layer (1 km) were significantly higher (similar to 1.9 and 12 mu g m(-3)), respectively. The BC (i.e BCtot) aerosol direct radiative forcing (DRF) values were estimated at the top of the atmosphere (TOA), surface (SFC), and atmosphere (ATM) and its resultant forcing were- 75.5 Wm(-2) at SFC indicating the cooling effect at the surface. A positive value (20.9 Wm(-2)) of BC aerosol DRF at TOA indicated the warming effect at the top of the atmosphere over the study region. The net DRF value due to BC aerosol was positive (96.4 Wm(-2)) indicating a net warming effect in the atmosphere. The contribution of fossil and biomass fuels to the observed BC aerosol DRF values was -78% and-22%, respectively. The higher mean atmospheric heating rate (2.71 K clay(-1)) by BC aerosol in the winter season would probably strengthen the temperature inversion leading to poor dispersion and affecting the formation of clouds. Serious detrimental impacts on regional climate due to the high concentrations of BC and PM (especially PM2.5) aerosol are likely based on this study and suggest the need for immediate, stringent measures to improve the regional air quality in the northern India.
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7.
  • Boyer, Matthew, et al. (författare)
  • A full year of aerosol size distribution data from the central Arctic under an extreme positive Arctic Oscillation : insights from the Multidisciplinarydrifting Observatory for the Study of Arctic Climate (MOSAiC) expedition
  • 2023
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 23:1, s. 389-415
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic environment is rapidly changing due to accelerated warming in the region. The warming trend is driving a decline in sea ice extent, which thereby enhances feedback loops in the surface energy budget in the Arctic. Arctic aerosols play an important role in the radiative balance and hence the climate response in the region, yet direct observations of aerosols over the Arctic Ocean are limited. In this study, we investigate the annual cycle in the aerosol particle number size distribution (PNSD), particle number concentration (PNC), and black carbon (BC) mass concentration in the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. This is the first continuous, year-long data set of aerosol PNSD ever collected over the sea ice in the central Arctic Ocean. We use a k-means cluster analysis, FLEXPART simulations, and inverse modeling to evaluate seasonal patterns and the influence of different source regions on the Arctic aerosol population. Furthermore, we compare the aerosol observations to land-based sites across the Arctic, using both long-term measurements and observations during the year of the MOSAiC expedition (2019–2020), to investigate interannual variability and to give context to the aerosol characteristics from within the central Arctic. Our analysis identifies that, overall, the central Arctic exhibits typical seasonal patterns of aerosols, including anthropogenic influence from Arctic haze in winter and secondary aerosol processes in summer. The seasonal pattern corresponds to the global radiation, surface air temperature, and timing of sea ice melting/freezing, which drive changes in transport patterns and secondary aerosol processes. In winter, the Norilsk region in Russia/Siberia was the dominant source of Arctic haze signals in the PNSD and BC observations, which contributed to higher accumulation-mode PNC and BC mass concentrations in the central Arctic than at land-based observatories. We also show that the wintertime Arctic Oscillation (AO) phenomenon, which was reported to achieve a record-breaking positive phase during January–March 2020, explains the unusual timing and magnitude of Arctic haze across the Arctic region compared to longer-term observations. In summer, the aerosol PNCs of the nucleation and Aitken modes are enhanced; however, concentrations were notably lower in the central Arctic over the ice pack than at land-based sites further south. The analysis presented herein provides a current snapshot of Arctic aerosol processes in an environment that is characterized by rapid changes, which will be crucial for improving climate model predictions, understanding linkages between different environmental processes, and investigating the impacts of climate change in future Arctic aerosol studies.
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8.
  • Brean, James, et al. (författare)
  • Collective geographical ecoregions and precursor sources driving Arctic new particle formation
  • 2023
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 23:3, s. 2183-2198
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic is a rapidly changing ecosystem, with complex ice–ocean–atmosphere feedbacks. An important process is new particle formation (NPF), from gas-phase precursors, which provides a climate forcing effect. NPF has been studied comprehensively at different sites in the Arctic, ranging from those in the High Arctic and those at Svalbard to those in the continental Arctic, but no harmonised analysis has been performed on all sites simultaneously, with no calculations of key NPF parameters available for some sites. Here, we analyse the formation and growth of new particles from six long-term ground-based stations in the Arctic (Alert, Villum, Tiksi, Zeppelin Mountain, Gruvebadet, and Utqiaġvik). Our analysis of particle formation and growth rates in addition to back-trajectory analysis shows a summertime maxima in the frequency of NPF and particle formation rate at all sites, although the mean frequency and particle formation rates themselves vary greatly between sites, with the highest at Svalbard and lowest in the High Arctic. The summertime growth rate, condensational sinks, and vapour source rates show a slight bias towards the southernmost sites, with vapour source rates varying by around an order of magnitude between the northernmost and southernmost sites. Air masses back-trajectories during NPF at these northernmost sites are associated with large areas of sea ice and snow, whereas events at Svalbard are associated with more sea ice and ocean regions. Events at the southernmost sites are associated with large areas of land and sea ice. These results emphasise how understanding the geographical variation in surface type across the Arctic is key to understanding secondary aerosol sources and providing a harmonised analysis of NPF across the Arctic.
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9.
  • Cirino, Glauber, et al. (författare)
  • Observations of Manaus urban plume evolution and interaction with biogenic emissions in GoAmazon 2014/5
  • 2018
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 191, s. 513-524
  • Tidskriftsartikel (refereegranskat)abstract
    • As part of the Observations and Modeling of the Green Ocean Amazon (GoAmazon 2014/5) Experiment, detailed aerosol and trace gas measurements were conducted near Manaus, a metropolis located in the central Amazon Basin. Measurements of aerosol particles and trace gases were done downwind Manaus at the sites T2 (Tiwa Hotel) and T3 (Manacapuru), at a distance of 8 and 70 km from Manaus, respectively. Based on in-plume measurements closer to Manaus (site T2), the chemical signatures of city emissions were used to improve the interpretation of pollutant levels at the T3 site. We derived chemical and physical properties for the city's atmospheric emission ensemble, taking into account only air masses impacted by the Manaus plume at both sites, during the wet and dry season Intensive Operating Periods (IOPs). At T2, average concentrations of aerosol number (CN), CO and SO2 were 5500 cm(-3) (between 10 and 490 nm), 145 ppb and 0.60 ppb, respectively, with a typical ratio ACN/ACO of 60-130 particles cm(-3) ppb(-1). The aerosol scattering (at RH < 60%) and absorption at 637 nm at T2 ranged from 10 to 50 M m(-1) and 5-10 M m(-1), respectively, leading to a mean single scattering albedo (SSA) of 0.70. In addition to identifying periods dominated by Manaus emissions at both T2 and T3, the plume transport between the two sampling sites was studied using back trajectory calculations. Results show that the presence of the Manaus plume at site T3 was important mainly during the daytime and at the end of the afternoons. During time periods directly impacted by Manaus emissions, an average aerosol number concentration of 3200 cm(-3) was measured at T3. Analysis of plume evolution between T2 and T3 indicates a transport time of 4-5 h. Changes of submicron organic and sulfate aerosols ratios relative to CO (Delta OA/Delta CO and Delta SO4/Delta CO, respectively) indicate significant production of secondary organic aerosol (SOA), corresponding to a 40% mass increase in OA and a 30% in SO4 mass concentration. Similarly, during air mass arrival at T3 the SSA increased to 0.83 from 0.70 at T2, mainly associated with an increase in organic aerosol concentration. Aerosol particle size distributions show a strong decrease in the Aitken nuclei mode (10-100 nm) during the transport from T2 to T3, in particular above 30 nm, as a result of efficient coagulation processes into larger particles. A decrease of 30% in the particle number concentration and an increase of about 50 nm in geometric mean diameter were observed from T2 to T3 sites. The study of the evolution of aerosol properties downwind of the city of Manaus improves our understanding of how coupling of anthropogenic and biogenic sources may be impacting the sensitive Amazonian atmosphere.
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10.
  • Cremer, Roxana S., et al. (författare)
  • Airmass Analysis of Size-Resolved Black Carbon Particles Observed in the Arctic Based on Cluster Analysis
  • 2022
  • Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 13:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Here we apply new analysis methods and approaches to existing long-term measurement series that provide additional insights into the atmospheric processes that control black carbon (BC) in the Arctic. Based on clustering size distribution data from Zeppelin Observatory for the years 2002–2010, observations classified as ‘Polluted’ were further investigated based on BC properties. The data were split into two subgroups, and while the microphysical and chemical fingerprints of the two subgroups are very similar, they show larger differences in BC concentration and correlation with the particle size distribution. Therefore, a source–receptor analysis was performed with HYSPLIT 10-days backward trajectories for both subsets. We demonstrate that within this ‘Polluted’ category, the airmasses that contributed to the largest BC signal at the Zeppelin station are not necessarily associated with traditional transport pathways from Eurasia. Instead, the strongest signal is from a region east of the Ural Mountains across the continent to the Kamchatka Peninsula.
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11.
  • Cremer, Roxana S., 1993- (författare)
  • Lifecycle of Black Carbon in the Arctic
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This PhD thesis investigates the atmospheric life cycle of Black Carbon (BC) in the Arctic. The Arctic region has been rapidly changing in the last decades and the role of BC aerosols in this is still uncertain. BC aerosols are mainly produced by incomplete combustion of biomass burning and fossil fuel and stand out from other aerosol species due to their strong ability to absorb solar radiation. The impact of BC on the Earth’s radiation budget is estimated to be overall warming. While the indirect effect, interactions with clouds, is estimated to be negative, the direct radiation effect is positive because of the absorption ability of the BC. These estimates are uncertain, especially for aerosol-cloud interactions. To estimate the role of BC in the Arctic, it is necessary to know the size distribution of BC, the transport pattern and the loss processes that affect the BC concentration. In this thesis, in-situ observations from the Zeppelin observatory in the Arctic, as well as global modelling tools, are used to answer the following research questions: 1. What kind of new insights about BC size distributions can be gained from simultaneous long-term measurements of absorption and aerosol number size distributions? 2. How do source regions impact BC size distributions measured at Zeppelin? 3. How are observations of biomass burning tracers at Zeppelin connected to transport from source regions with active fires? 4. How do emissions, as well as, wet and dry removal pathways drive the diversity of the BC life cycle in General Circulation Models (GCMs)?A statistical method to derive BC size distributions from filter-based absorption measurements was developed and applied to long-term data from the Arctic measurement station Zeppelin on Svalbard. Promising results were obtained for inferring BC number size distributions from absorption and size distribution data, except for the most polluted conditions with the air masses arriving from Northern Eurasia and Russia - as identified from an analysis using back trajectories. Trajectory analysis was also used to link events with elevated biomass burning tracers and BC at Zeppelin to fire activity measured by satellites on the continents around the Arctic. To investigate the interplay of emissions and removal processes of BC in models and to understand the diversity in model representation of BC in the Arctic, a detailed analysis of processes in four GCMs was performed. The BC concentrations in the Arctic were compared and their response to removal processes during long-range transport to Zeppelin. The results underline the importance of BC sources and processing far away from the Arctic.The knowledge gained about the BC life cycle will facilitate a better assessment of the large-scale influence of BC on the Arctic climate and environment.
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12.
  • Croft, Betty, et al. (författare)
  • Processes controlling the annual cycle of Arctic aerosol number and size distributions
  • 2016
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:6, s. 3665-3682
  • Tidskriftsartikel (refereegranskat)abstract
    • Measurements at high-Arctic sites (Alert, Nunavut, and Mt. Zeppelin, Svalbard) during the years 2011 to 2013 show a strong and similar annual cycle in aerosol number and size distributions. Each year at both sites, the number of aerosols with diameters larger than 20 nm exhibits a minimum in October and two maxima, one in spring associated with a dominant accumulation mode (particles 100 to 500 nm in diameter) and a second in summer associated with a dominant Aitken mode (particles 20 to 100 nm in diameter). Seasonal-mean aerosol effective diameter from measurements ranges from about 180 in summer to 260 nm in winter. This study interprets these annual cycles with the GEOS-Chem-TOMAS global aerosol microphysics model. Important roles are documented for several processes (new-particle formation, coagulation scavenging in clouds, scavenging by precipitation, and transport) in controlling the annual cycle in Arctic aerosol number and size. Our simulations suggest that coagulation scavenging of interstitial aerosols in clouds by aerosols that have activated to form cloud droplets strongly limits the total number of particles with diameters less than 200 nm throughout the year. We find that the minimum in total particle number in October can be explained by diminishing new-particle formation within the Arctic, limited transport of pollution from lower latitudes, and efficient wet removal. Our simulations indicate that the summertime-dominant Aitken mode is associated with efficient wet removal of accumulation-mode aerosols, which limits the condensation sink for condensable vapours. This in turn promotes new-particle formation and growth. The dominant accumulation mode during spring is associated with build up of transported pollution from outside the Arctic coupled with less-efficient wet-removal processes at colder temperatures. We recommend further attention to the key processes of new-particle formation, interstitial coagulation, and wet removal and their delicate interactions and balance in size-resolved aerosol simulations of the Arctic to reduce uncertainties in estimates of aerosol radiative effects on the Arctic climate.
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13.
  • Dal Maso, Miikka, et al. (författare)
  • Annual and interannual variation in boreal forest aerosol particle number and volume concentration and their connection to particle formation
  • 2008
  • Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60:4, s. 495-508
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated size-resolved submicrometre aerosol particle number and volume concentration time series as well as aerosol dynamic parameters derived front Differential Mobility Particle Sizer (DMPS) measurements at five background stations in the Nordic boreal forest area. The stations in question were Aspvreten, Hyytiala and Uto in Southern Finland and Sweden, and Varrio and Pallas in the Finnish Lapland. The objective Of Our investigation was to identify and quantity annual and interannual variation observable in the time series. We found that the total number and mass concentrations were touch lower at the Lapland stations than at the southern stations and that the total particle number was strongly correlated to particle formation event frequency. The annual total number concentration followed the annual distribution of particle formation events at the Southern stations but much less clearly at the Lapland stations. The volume concentration was highest during summer, in line with higher condensation growth rates: this is in line with the assumption that a large part of the particle volume is produced by oxidized plant emissions. The decrease of sulphate emissions in Europe was not visible in our data set. Aerosol dynamic parameters such as condensation sink, condensation sink diameter and the power law exponent linking coagulation losses and condensation sink are presented to characterize the submicron Nordic background aerosol.
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14.
  • Dall' Osto, M., et al. (författare)
  • Arctic sea ice melt leads to atmospheric new particle formation
  • 2017
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • Atmospheric new particle formation (NPF) and growth significantly influences climate by supplying new seeds for cloud condensation and brightness. Currently, there is a lack of understanding of whether and how marine biota emissions affect aerosol-cloud-climate interactions in the Arctic. Here, the aerosol population was categorised via cluster analysis of aerosol size distributions taken at Mt Zeppelin (Svalbard) during a 11 year record. The daily temporal occurrence of NPF events likely caused by nucleation in the polar marine boundary layer was quantified annually as 18%, with a peak of 51% during summer months. Air mass trajectory analysis and atmospheric nitrogen and sulphur tracers link these frequent nucleation events to biogenic precursors released by open water and melting sea ice regions. The occurrence of such events across a full decade was anti-correlated with sea ice extent. New particles originating from open water and open pack ice increased the cloud condensation nuclei concentration background by at least ca. 20%, supporting a marine biosphere-climate link through sea ice melt and low altitude clouds that may have contributed to accelerate Arctic warming. Our results prompt a better representation of biogenic aerosol sources in Arctic climate models.
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15.
  • Dall'Osto, Manuel, et al. (författare)
  • Simultaneous measurements of aerosol size distributions at three sites in the European high Arctic
  • 2019
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:11, s. 7377-7395
  • Tidskriftsartikel (refereegranskat)abstract
    • Aerosols are an integral part of the Arctic climate system due to their direct interaction with radiation and indirect interaction through cloud formation. Understanding aerosol size distributions and their dynamics is crucial for the ability to predict these climate relevant effects. When of favourable size and composition, both long-rangetransported - and locally formed particles - may serve as cloud condensation nuclei (CCN). Small changes of composition or size may have a large impact on the low CCN concentrations currently characteristic of the Arctic environment. We present a cluster analysis of particle size distributions (PSDs; size range 8-500 nm) simultaneously collected from three high Arctic sites during a 3-year period (20132015). Two sites are located in the Svalbard archipelago: Zeppelin research station (ZEP; 474 m above ground) and the nearby Gruvebadet Observatory (GRU; about 2 km distance from Zeppelin, 67 m above ground). The third site (Villum Research Station at Station Nord, VRS; 30 m above ground) is 600 km west-northwest of Zeppelin, at the tip of northeastern Greenland. The GRU site is included in an inter-site comparison for the first time. K-means cluster analysis pro- vided eight specific aerosol categories, further combined into broad PSD classes with similar characteristics, namely pristine low concentrations (12 %-14 % occurrence), new particle formation (16 %-32 %), Aitken (21 %-35 %) and accumulation (20 %-50 %). Confined for longer time periods by consolidated pack sea ice regions, the Greenland site GRU shows PSDs with lower ultrafine-mode aerosol concentrations during summer but higher accumulation-mode aerosol concentrations during winter, relative to the Svalbard sites. By association with chemical composition and cloud condensation nuclei properties, further conclusions can be derived. Three distinct types of accumulation-mode aerosol are observed during winter months. These are associated with sea spray (largest detectable sizes, > 400 nm), Arctic haze (main mode at 150 nm) and aged accumulation-mode (main mode at 220 nm) aerosols. In contrast, locally produced particles, most likely of marine biogenic origin, exhibit size distributions dominated by the nucleation and Aitken mode during summer months. The obtained data and analysis point towards future studies, including apportioning the relative contribution of primary and secondary aerosol formation processes and elucidating anthropogenic aerosol dynamics and transport and removal processes across the Greenland Sea. In order to address important research questions in the Arctic on scales beyond a singular station or measurement events, it is imperative to continue strengthening international scientific cooperation.
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16.
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17.
  • Engvall, Ann-Christine, et al. (författare)
  • The radiative effect of an aged, internally mixed Arctic aerosol originating from lower-latitude biomass burning
  • 2009
  • Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 61:4, s. 677-684
  • Tidskriftsartikel (refereegranskat)abstract
    • Arctic-haze layers and their radiative effects have been investigated previously in numerous studies as they are known to have an impact on the regional climate. In this study, we report on an event of an elevated aerosol layer, notably consisting of high-absorbing soot particles, observed in the European Arctic free troposphere the 2007 April 14 during the ASTAR 2007 campaign. The ca. 0.5 km vertically thick aerosol layer located at an altitude of around 3 km had a particle-size distribution mode around 250 nm diameter. In this study, we quantify the radiative effect aerosol layers have on the Arctic atmosphere by using in situ observations. Measurements of particles size segregated temperature stability using thermal denuders, indicate that the aerosol in the optically active size range was chemically internally mixed. In the plume, maximum observed absorption and scattering coefficients were 3 x 10(-6) and 20 x 10(-6) m(-1), respectively. Observed microphysical and optical properties were used to constrain calculations of heating rates of an internally mixed aerosol assuming two different surface albedos that represent snow/ice covered and open ocean. The average profile resulted in a heating rate in the layer of 0.2 K d(-1) for the high-albedo case and 0.15 K d(-1) for the low albedo case. This calculated dependence on albedo based on actual observations corroborates previous numerical simulations. The heating within the plume resulted in a measurable signal shown as an enhancement in the temperature of a few tenths of a degree. Although the origin of the aerosol plume could not unambiguously be determined, the microphysical properties of the aerosol had strong similarities with previously reported biomass burning plumes. With a changing climate, short-lived pollutants such as biomass plumes may become more frequent in the Arctic and have important radiative effects at regional scale.
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18.
  • Evangeliou, N., et al. (författare)
  • Wildfires in northern Eurasia affect the budget of black carbon in the Arctic - a 12-year retrospective synopsis (2002-2013)
  • 2016
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:12, s. 7587-7604
  • Tidskriftsartikel (refereegranskat)abstract
    • In recent decades much attention has been given to the Arctic environment, where climate change is happening rapidly. Black carbon (BC) has been shown to be a major component of Arctic pollution that also affects the radiative balance. In the present study, we focused on how vegetation fires that occurred in northern Eurasia during the period of 2002-2013 influenced the budget of BC in the Arctic. For simulating the transport of fire emissions from northern Eurasia to the Arctic, we adopted BC fire emission estimates developed independently by GFED3 (Global Fire Emissions Database) and FEI-NE (Fire Emission Inventory - northern Eurasia). Both datasets were based on fire locations and burned areas detected by MODIS (Moderate resolution Imaging Spectroradiometer) instruments on NASA's (National Aeronautics and Space Administration) Terra and Aqua satellites. Anthropogenic sources of BC were adopted from the MACCity (Monitoring Atmospheric Composition and Climate and megacity Zoom for the Environment) emission inventory. During the 12-year period, an average area of 250aEuro-000aEuro-km(2)aEuro-yr(-1) was burned in northern Eurasia (FEI-NE) and the global emissions of BC ranged between 8.0 and 9.5aEuro-TgaEuro-yr(-1) (FEI-NE+MACCity). For the BC emitted in the Northern Hemisphere (based on FEI-NE+MACCity), about 70aEuro-% originated from anthropogenic sources and the rest from biomass burning (BB). Using the FEI-NE+MACCity inventory, we found that 102aEuro-+/- aEuro-29aEuro-ktaEuro-yr(-1) BC was deposited in the Arctic (defined here as the area north of 67A degrees aEuro-N) during the 12 years simulated, which was twice as much as when using the MACCity inventory (56aEuro-+/- aEuro-8aEuro-ktaEuro-yr(-1)). The annual mass of BC deposited in the Arctic from all sources (FEI-NE in northern Eurasia, MACCity elsewhere) is significantly higher by about 37aEuro-% in 2009 (78 vs. 57aEuro-ktaEuro-yr(-1)) to 181aEuro-% in 2012 (153 vs. 54aEuro-ktaEuro-yr(-1)), compared to the BC deposited using just the MACCity emission inventory. Deposition of BC in the Arctic from BB sources in the Northern Hemisphere thus represents 68aEuro-% of the BC deposited from all BC sources (the remaining being due to anthropogenic sources). Northern Eurasian vegetation fires (FEI-NE) contributed 85aEuro-% (79-91aEuro-%) to the BC deposited over the Arctic from all BB sources in the Northern Hemisphere. We estimate that about 46aEuro-% of the BC deposited over the Arctic from vegetation fires in northern Eurasia originated from Siberia, 6aEuro-% from Kazakhstan, 5aEuro-% from Europe, and about 1aEuro-% from Mongolia. The remaining 42aEuro-% originated from other areas in northern Eurasia. About 42aEuro-% of the BC released from northern Eurasian vegetation fires was deposited over the Arctic (annual average: 17aEuro-%) during spring and summer.
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19.
  • Franke, Vera, et al. (författare)
  • Chemical composition and source analysis of carbonaceous aerosol particles at a mountaintop site in central Sweden
  • 2017
  • Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 69
  • Tidskriftsartikel (refereegranskat)abstract
    • The chemical composition of atmospheric particulate matter at Mt. angstrom reskutan, a mountaintop site in central Sweden, was analysed with a focus on its carbonaceous content. Filter samples taken during the Cloud and Aerosol Experiment at angstrom re (CAEsAR 2014) were analysed by means of a thermo-optical method and ion chromatography. Additionally, the particle light absorption and particle number size distribution measurements for the entire campaign were added to the analysis. Mean airborne concentrations of organic and elemental carbon during CAEsAR 2014 were OC= 0.85 +/- 0.8 mu gm(-3) and EC = 0.06 +/- 0.06 mu gm(-3), respectively. Elemental to organic carbon ratios varied between EC/OC = 0.02 and 0.19. During the study a large wildfire occurred in Vastmanland, Sweden, with the plume reaching our study site. This led to significant increases in OC and EC concentrations (OC = 3.04 +/- 0.03 mu gm(-3) and EC = 0.24 +/- 0.00 mu gm(-3)). The mean mass-specific absorption coefficient observed during the campaign was sigma(BC)(abs) = 9.1 +/- 7.3 m(2)g(-1) (at wavelength lambda= 637 nm). In comparison to similarly remote European sites, Mt. angstrom reskutan experienced significantly lower carbonaceous aerosol loadings with a clear dominance of organic carbon. A mass closure study revealed a missing chemical mass fraction that likely originated from mineral dust. Potential regional source contributions of the carbonaceous aerosol were investigated using modelled air mass back trajectories. This source apportionment pointed to a correlation between high EC concentrations and air originating from continental Europe. Particles rich in organic carbon most often arrived from highly vegetated continental areas. However, marine regions were also a source of these aerosol particles. The source contributions derived during this study were compared to emission inventories of an Earth system model. This comparison highlighted a lack of OC and EC point-sources in the model's emission inventory which could potentially lead to an underestimation of the carbonaceous aerosol reaching Mt. angstrom reskutan in the simulation of this Earth system model.
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20.
  • Fredricsson, Malin, et al. (författare)
  • Nationell luftövervakning Sakrapport med data från övervakning inom Programområde Luft t.o.m 2019
  • 2021
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Naturvårdsverket ansvarar för den nationella luftövervakningen i bakgrundsmiljö i Sverige. I rapporten redovisas resultat från verksamheten inom Programområde Luft avseende mätningar (genomförda av IVL, SU, SLU och SMHI) till och med 2019 och regionala modellberäkningar (utförda av SMHI) till och med 2018.För flertalet av de luftföroreningskomponenter som övervakas inom den nationella miljöövervakningen har det, sedan mätningarna startade för mellan 20 och 40 år sedan, generellt sett skett en avsevärd förbättring avseende såväl halter i luft som deposition i bakgrundsmiljö. Utvecklingen har dock varierat i något olika utsträckning beroende på komponenter och lokalisering i landet. Föroreningsbelastningen är oftast lägre ju längre norrut i landet man kommer.För de flesta ämnen som det finns miljökvalitetsnormer (MKN) respektive miljömål för ligger halterna i regional bakgrund avsevärt lägre än angivna gräns- och målvärden. Halterna av ozon överskrider dock i dagsläget (2019) MKN för hälsa.
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21.
  • Freud, E., et al. (författare)
  • Anthropogenic aerosol effects on convective cloud microphysical properties in southern Sweden
  • 2008
  • Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60:2, s. 286-297
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we look for anthropogenic aerosol effects in southern Scandinavia's clouds under the influence of moderate levels of pollution and relatively weak dynamic forcing. This was done by comparing surface aerosol measurements with convective cloud microphysical profiles produced from satellite image analyses. The results show that the clouds associated with the anthropogenic-affected air with high PM0.5, had to acquire a vertical development of similar to 3.5 km before forming precipitation-sized particles, compared to less than 1 km for the clouds associated with low PM0.5 air-masses. Additionally, a comparison of profiles with precipitation was done with regard to different potentially important parameters. For precipitating clouds the variability of the cloud thickness needed to produce the precipitation (Delta h(14)) is directly related to PM0.5 concentrations, even without considering atmospheric stability, the specific aerosol size distribution or the aerosols' chemical composition. Each additional 1 mu g m(-3) of PM0.5 was found to increase Delta h(14) by similar to 200-250 m. Our conclusion is that it is indeed possible to detect the effects of anthropogenic aerosol on the convective clouds in southern Scandinavia despite modest aerosol masses. It also emphasizes the importance of including aerosol processes in climate-radiation models and in numerical weather prediction models.
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22.
  • Freud, Eyal, et al. (författare)
  • Pan-Arctic aerosol number size distributions : seasonality and transport patterns
  • 2017
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:13, s. 8101-8128
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic environment has an amplified response to global climatic change. It is sensitive to human activities that mostly take place elsewhere. For this study, a multi-year set of observed aerosol number size distributions in the diameter range of 10 to 500 nm from five sites around the Arctic Ocean (Alert, Villum Research Station - Station Nord, Zeppelin, Tiksi and Barrow) was assembled and analysed. A cluster analysis of the aerosol number size distributions revealed four distinct distributions. Together with Lagrangian air parcel back-trajectories, they were used to link the observed aerosol number size distributions with a variety of transport regimes. This analysis yields insight into aerosol dynamics, transport and removal processes, on both an intra- and an inter-monthly scale. For instance, the relative occurrence of aerosol number size distributions that indicate new particle formation (NPF) event is near zero during the dark months, increases gradually to similar to 40% from spring to summer, and then collapses in autumn. Also, the likelihood of Arctic haze aerosols is minimal in summer and peaks in April at all sites. The residence time of accumulation-mode particles in the Arctic troposphere is typically long enough to allow tracking them back to their source regions. Air flow that passes at low altitude over central Siberia and western Russia is associated with relatively high concentrations of accumulation-mode particles (N-acc) at all five sites - often above 150 cm(-3). There are also indications of air descending into the Arctic boundary layer after transport from lower latitudes. The analysis of the back-trajectories together with the meteorological fields along them indicates that the main driver of the Arctic annual cycle of N-acc, on the larger scale, is when atmospheric transport covers the source regions for these particles in the 10-day period preceding the observations in the Arctic. The scavenging of these particles by precipitation is shown to be important on a regional scale and it is most active in summer. Cloud processing is an additional factor that enhances the N-acc annual cycle. There are some consistent differences between the sites that are beyond the year-to-year variability. They are the result of differences in the proximity to the aerosol source regions and to the Arctic Ocean sea-ice edge, as well as in the exposure to free-tropospheric air and in precipitation patterns - to mention a few. Hence, for most purposes, aerosol observations from a single Arctic site cannot represent the entire Arctic region. Therefore, the results presented here are a powerful observational benchmark for evaluation of detailed climate and air chemistry modelling studies of aerosols throughout the vast Arctic region.
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23.
  • Giamarelou, Maria, et al. (författare)
  • Indirect evidence of the composition of nucleation mode atmospheric particles in the high Arctic
  • 2016
  • Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 121:2, s. 965-975
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous long-term observations have shown that nanoparticle formation events are common in the summer-time high Arctic and linked to local photochemical activity. However, current knowledge is limited with respect to the chemical precursors of resulting nanoparticles and the compounds involved in their subsequent growth. Here we report case-study measurements during new particle formation (NPF) events of the particle size distribution (diameter>7nm) and for the first time the volatility of monodisperse particles having diameter 40nm, providing indirect information about their composition. Volatility measurements provide indirect evidence that a predominant fraction of the 12nm particle population is ammoniated sulfates in the summertime high Arctic. Our observations further suggest that the majority of the sub-40nm particle population during NPF events does not exist in the form of sulfuric acid but rather as partly or fully neutralized ammoniated sulfates.
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24.
  • Grythe, Henrik, 1980-, et al. (författare)
  • A new aerosol wet removal scheme for the Lagrangian particle model FLEXPART
  • 2017
  • Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 10:4, s. 1447-1466
  • Tidskriftsartikel (refereegranskat)abstract
    • A new and more physically based treatment of how removal by precipitation is calculated by FLEXPART is introduced, to take into account more aspects of aerosol diversity. Also new, is the definition of clouds and cloud properties. Results from simulations show good agreement with observed atmospheric concentrations for distinctly different aerosols. Atmospheric lifetimes were found to vary from a few hours (large aerosol particles) up to a month (small non-soluble).
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25.
  • Hamburger, Thomas, et al. (författare)
  • Long-term in situ observations of biomass burning aerosol at a high altitude station in Venezuela - sources, impacts and interannual variability
  • 2013
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 13:19, s. 9837-9853
  • Tidskriftsartikel (refereegranskat)abstract
    • First long-term observations of South American biomass burning aerosol within the tropical lower free troposphere are presented. The observations were conducted between 2007 and 2009 at a high altitude station (4765 m a.s.l.) on the Pico Espejo, Venezuela. Sub-micron particle volume, number concentrations of primary particles and particle absorption were observed. Orographic lifting and shallow convection leads to a distinct diurnal cycle at the station. It enables measurements within the lower free troposphere during night-time and observations of boundary layer air masses during daytime and at their transitional regions. The seasonal cycle is defined by a wet rainy season and a dry biomass burning season. The particle load of biomass burning aerosol is dominated by fires in the Venezuelan savannah. Increases of aerosol concentrations could not be linked to long-range transport of biomass burning plumes from the Amazon basin or Africa due to effective wet scavenging of particles. Highest particle concentrations were observed within boundary layer air masses during the dry season. Ambient sub-micron particle volume reached 1.4 +/- 1.3 mu m(3) cm(-3), refractory particle number concentrations (at 300 degrees C) 510+/-420 cm(-3) and the absorption coefficient 0.91+/-1.2 Mm(-1). The respective concentrations were lowest within the lower free troposphere during the wet season and averaged at 0.19+/-0.25 mu m(3) cm-3, 150+/-94 cm(-3) and 0.15+/-0.26 Mm(-1). A decrease of particle concentrations during the dry seasons from 2007-2009 could be connected to a decrease in fire activity in the wider region of Venezuela using MODIS satellite observations. The variability of biomass burning is most likely linked to the El Nino-Southern Oscillation (ENSO). Low biomass burning activity in the Venezuelan savannah was observed to follow La Nina conditions, high biomass burning activity followed El Nino conditions.
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26.
  • Hansen, A. M. K., et al. (författare)
  • Organosulfates and organic acids in Arctic aerosols : speciation, annual variation and concentration levels
  • 2014
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:15, s. 7807-7823
  • Tidskriftsartikel (refereegranskat)abstract
    • Sources, composition and occurrence of secondary organic aerosols in the Arctic were investigated at Zeppelin Mountain, Svalbard, and Station Nord, northeastern Greenland, during the full annual cycle of 2008 and 2010, respectively. Speciation of organic acids, organosulfates and nitrooxy organosulfates - from both anthropogenic and biogenic precursors were in focus. A total of 11 organic acids (terpenylic acid, benzoic acid, phthalic acid, pinic acid, suberic acid, azelaic acid, adipic acid, pimelic acid, pinonic acid, diaterpenylic acid acetate and 3-methyl-1,2,3-butanetricarboxylic acid), 12 organosulfates and 1 nitrooxy organosulfate were identified in aerosol samples from the two sites using a high-performance liquid chromatograph (HPLC) coupled to a quadrupole Time-of-Flight mass spectrometer. At Station Nord, compound concentrations followed a distinct annual pattern, where high mean concentrations of organosulfates (47 +/- 14 ng m(-3)) and organic acids (11.5 +/- 4 ng m(-3)) were observed in January, February and March, contrary to considerably lower mean concentrations of organosulfates (2 +/- 3 ng m(3-)) and organic acids (2.2 +/- 1 ng m(-3)) observed during the rest of the year. At Zeppelin Mountain, organosulfate and organic acid concentrations remained relatively constant during most of the year at a mean concentration of 15 +/- 4 ng m(-3) and 3.9 +/- 1 ng m(-3), respectively. However during four weeks of spring, remarkably higher concentrations of total organosulfates (23-36 ng m(-3)) and total organic acids (7-10 ngm(-3)) were observed. Elevated organosulfate and organic acid concentrations coincided with the Arctic haze period at both stations, where northern Eurasia was identified as the main source region. Air mass transport from northern Eurasia to Zeppelin Mountain was associated with a 100% increase in the number of detected organosulfate species compared with periods of air mass transport from the Arctic Ocean, Scandinavia and Greenland. The results from this study suggested that the presence of organic acids and organosulfates at Station Nord was mainly due to long-range transport, whereas indications of local sources were found for some compounds at Zeppelin Mountain. Furthermore, organosulfates contributed significantly to organic matter throughout the year at Zeppelin Mountain (annual mean of 13 +/- 8 %) and during Arctic haze at Station Nord (7 +/- 2 %), suggesting organosulfates to be important compounds in Arctic aerosols.
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27.
  • Hansson, Hans-Christen, et al. (författare)
  • The Atmospheric Aerosol over Western Greece-Six Years of Aerosol Observations at the Navarino Environmental Observatory
  • 2021
  • Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 12:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The Eastern Mediterranean is a highly populated area with air quality problems. It is also where climate change is already noticed by higher temperatures and s changing precipitation pattern. The anthropogenic aerosol affects health and changing concentrations and properties of the atmospheric aerosol affect radiation balance and clouds. Continuous long-term observations are essential in assessing the influence of anthropogenic aerosols on climate and health. We present six years of observations from Navarino Environmental Observatory (NEO), a new station located at the south west tip of Peloponnese, Greece. The two sites at NEO, were evaluated to show the influence of the local meteorology and to assess the general background aerosol possible. It was found that the background aerosol was originated from aged European aerosols and was strongly influenced by biomass burning, fossil fuel combustion, and industry. When subsiding into the boundary layer, local sources contributed in the air masses moving south. Mesoscale meteorology determined the diurnal variation of aerosol properties such as mass and number by means of typical sea breeze circulation, giving rise to pronounced morning and evening peaks in pollutant levels. While synoptic scale meteorology, mainly large-scale air mass transport and precipitation, strongly influenced the seasonality of the aerosol properties.
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28.
  • Heintzenberg, Jost, et al. (författare)
  • New particle formation in the Svalbard region 2006-2015
  • 2017
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:10, s. 6153-6175
  • Tidskriftsartikel (refereegranskat)abstract
    • Events of new particle formation (NPF) were analyzed in a 10-year data set of hourly particle size distributions recorded on Mt. Zeppelin, Spitsbergen, Svalbard. Three different types of NPF events were identified through objective search algorithms. The first and simplest algorithm utilizes short-term increases in particle concentrations below 25 nm (PCT (percentiles) events). The second one builds on the growth of the sub-50 nm diameter median (DGR (diameter growth) events) and is most closely related to the classical banana type of event. The third and most complex, multiple-size approach to identifying NPF events builds on a hypothesis suggesting the concurrent production of polymer gel particles at several sizes below ca. 60 nm (MEV (multisize growth) events). As a first and general conclusion, we can state that NPF events are a summer phenomenon and not related to Arctic haze, which is a late winter to early spring feature. The occurrence of NPF events appears to be somewhat sensitive to the available data on precipitation. The seasonal distribution of solar flux suggests some photochemical control that may affect marine biological processes generating particle precursors and/or atmospheric photochemical processes that generate condensable vapors from precursor gases. Notably, the seasonal distribution of the biogenic methanesulfonate (MSA) follows that of the solar flux although it peaks before the maxima in NPF occurrence. A host of ancillary data and findings point to varying and rather complex marine biological source processes. The potential source regions for all types of new particle formation appear to be restricted to the marginal-ice and open-water areas between northeastern Greenland and eastern Svalbard.Depending on conditions, yet to be clarified new particle formation may become visible as short bursts of particles around 20 nm (PCT events), longer events involving condensation growth (DGR events), or extended events with elevated concentrations of particles at several sizes below 100 nm (MEV events). The seasonal distribution of NPF events peaks later than that of MSA and DGR, and in particular than that of MEV events, which reach into late summer and early fall with open, warm, and biologically active waters around Svalbard. Consequently, a simple model to describe the seasonal distribution of the total number of NPF events can be based on solar flux and sea surface temperature, representing environmental conditions for marine biological activity and condensation sink, controlling the balance between new particle nucleation and their condensational growth. Based on the sparse knowledge about the seasonal cycle of gel-forming marine microorganisms and their controlling factors, we hypothesize that the seasonal distribution of DGR and, more so, MEV events reflect the seasonal cycle of the gel-forming phytoplankton.
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29.
  • Heintzenberg, J., et al. (författare)
  • Potential source regions and processes of aerosol in the summer Arctic
  • 2015
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 15:11, s. 6487-6502
  • Tidskriftsartikel (refereegranskat)abstract
    • Sub-micrometer particle size distributions measured during four summer cruises of the Swedish icebreaker Oden 1991, 1996, 2001, and 2008 were combined with dimethyl sulfide gas data, back trajectories, and daily maps of pack ice cover in order to investigate source areas and aerosol formation processes of the boundary layer aerosol in the central Arctic. With a clustering algorithm, potential aerosol source areas were explored. Clustering of particle size distributions together with back trajectories delineated five potential source regions and three different aerosol types that covered most of the Arctic Basin: marine, newly formed and aged particles over the pack ice. Most of the pack ice area with <15% of open water under the trajectories exhibited the aged aerosol type with only one major mode around 40 nm. For newly formed particles to occur, two conditions had to be fulfilled over the pack ice: the air had spent 10 days while traveling over ever more contiguous ice and had traveled over less than 30% open water during the last 5 days. Additionally, the air had experienced more open water (at least twice as much as in the cases of aged aerosol) during the last 4 days before arrival in heavy ice conditions at Oden. Thus we hypothesize that these two conditions were essential factors for the formation of ultrafine particles over the central Arctic pack ice. In a comparison the Oden data with summer size distribution data from Alert, Nunavut, and Mt. Zeppelin, Spitsbergen, we confirmed the Oden findings with respect to particle sources over the central Arctic. Future more frequent broken-ice or open water patches in summer will spur biological activity in surface water promoting the formation of biological particles. Thereby low clouds and fogs and subsequently the surface energy balance and ice melt may be affected.
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30.
  • Heslin-Rees, Dominic, et al. (författare)
  • From a polar to a marine environment : has the changing Arctic led to a shift in aerosol light scattering properties?
  • 2020
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:21, s. 13671-13686
  • Tidskriftsartikel (refereegranskat)abstract
    • The study of long-term trends in aerosol optical properties is an important task to understand the underlying aerosol processes influencing the change of climate. The Arctic, as the place where climate change manifests most, is an especially sensitive region of the world. Within this work, we use a unique long-term data record of key aerosol optical properties from the Zeppelin Observatory, Svalbard, to ask the question of whether the environmental changes of the last 2 decades in the Arctic are reflected in the observations. We perform a trend analysis of the measured particle light scattering and backscattering coefficients and the derived scattering Angstrom exponent and hemispheric backscattering fraction. In contrast to previous studies, the effect of in-cloud scavenging and of potential sampling losses at the site are taken explicitly into account in the trend analysis. The analysis is combined with a back trajectory analysis and satellite-derived sea ice data to support the interpretation of the observed trends. We find that the optical properties of aerosol particles have undergone clear and significant changes in the past 2 decades. The scattering Angstrom exponent exhibits statistically significant decreasing of between -4.9 % yr(-1) and -6.5 % yr(-1) (using wavelengths of lambda = 450 and 550 nm), while the particle light scattering coefficient exhibits statistically significant increasing trends of between 2.6 % yr(-1) and 2.9 % yr(-1) (at a wavelength of lambda = 550 nm). The magnitudes of the trends vary depending on the season. These trends indicate a shift to an aerosol dominated more by coarse-mode particles, most likely the result of increases in the relative amount of sea spray aerosol. We show that changes in air mass circulation patterns, specifically an increase in air masses from the south-west, are responsible for the shift in aerosol optical properties, while the decrease of Arctic sea ice in the last 2 decades only had a marginal influence on the observed trends.
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31.
  • Heslin-Rees, Dominic, 1993-, et al. (författare)
  • Increase in precipitation scavenging contributes to long-term reductions of light-absorbing aerosol in the Arctic
  • 2024
  • Ingår i: Atmospheric Chemistry And Physics. - 1680-7316 .- 1680-7324. ; 24:4, s. 2059-2075
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated long-term changes using a harmonised 22-year data set of aerosol light absorption measurements, in conjunction with air mass history and aerosol source analysis. The measurements were performed at Zeppelin Observatory, Svalbard, from 2002 to 2023. We report a statistically significant decreasing long-term trend for the light absorption coefficient. However, the last 8 years of 2016–2023 showed a slight increase in the magnitude of the light absorption coefficient for the Arctic haze season. In addition, we observed an increasing trend in the single-scattering albedo from 2002 to 2023. Five distinct source regions, representing different transport pathways, were identified. The trends involving air masses from the five regions showed decreasing absorption coefficients, except for the air masses from Eurasia. We show that the changes in the occurrences of each transport pathway cannot explain the reductions in the absorption coefficient observed at the Zeppelin station. An increase in contributions of air masses from more marine regions, with lower absorption coefficients, is compensated for by an influence from high-emission regions. The proportion of air masses en route to Zeppelin, which have been influenced by active fires, has undergone a noticeable increase starting in 2015. However, this increase has not impacted the long-term trends in the concentration of light-absorbing aerosol. Along with aerosol optical properties, we also show an increasing trend in accumulated surface precipitation experienced by air masses en route to the Zeppelin Observatory. We argue that the increase in precipitation, as experienced by air masses arriving at the station, can explain a quarter of the long-term reduction in the light absorption coefficient. We emphasise that meteorological conditions en route to the Zeppelin Observatory are critical for understanding the observed trends.
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32.
  • Hoffmann, Anne, et al. (författare)
  • Remote sensing and in situ measurements of tropospheric aerosol, a pamarcmip case study
  • 2012
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 52, s. 56-66
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, a closure experiment for tropospheric aerosol is presented. Aerosol size distributions and single scattering albedo from remote sensing data are compared to those measured in-situ. An aerosol pollution event on 4 April 2009 was observed by ground based and airborne lidar and photometer in and around Ny-Alesund, Spitsbergen, as well as by DMPS, nephelometer and particle soot absorption photometer at the nearby Zeppelin Mountain Research Station. The presented measurements were conducted in an area of 40 x 20 km around Ny-Alesund as part of the 2009 Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project (PAMARCMiP). Aerosol mainly in the accumulation mode was found in the lower troposphere, however, enhanced backscattering was observed up to the tropopause altitude. A comparison of meteorological data available at different locations reveals a stable multi-layer-structure of the lower troposphere. It is followed by the retrieval of optical and microphysical aerosol parameters. Extinction values have been derived using two different methods, and it was found that extinction (especially in the UV) derived from Raman lidar data significantly surpasses the extinction derived from photometer AOD profiles. Airborne lidar data shows volume depolarization values to be less than 2.5% between 500 m and 2.5 km altitude, hence, particles in this range can be assumed to be of spherical shape. In-situ particle number concentrations measured at the Zeppelin Mountain Research Station at 474 m altitude peak at about 0.18 mu m diameter, which was also found for the microphysical inversion calculations performed at 850 m and 1500 m altitude. Number concentrations depend on the assumed extinction values, and slightly decrease with altitude as well as the effective particle diameter. A low imaginary part in the derived refractive index suggests weakly absorbing aerosols, which is confirmed by low black carbon concentrations, measured at the Zeppelin Mountain as well as on board the Polar 5 aircraft.
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33.
  • Hussein, T., et al. (författare)
  • Time span and spatial scale of regional new particle formation events over Finland and Southern Sweden
  • 2009
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9:14, s. 4699-4716
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated the time span and spatial scale of regional new particle formation (NPF) events in Finland and Southern Sweden using measured particle number size distributions at five background stations. We define the time span of a NPF event as the time period from the first moment when the newly formed mode of aerosol particles is observable below 25 nm until the newly formed mode is not any more distinguishable from other background modes of aerosol particles after growing to bigger sizes. We identify the spatial scale of regional NPF events based on two independent approaches. The first approach is based on the observation within a network of stationary measurement stations and the second approach is based on the time span and the history of air masses back-trajectories. According to the second approach, about 60% and 28% of the events can be traced to distances longer than 220 km upwind from where the events were observed in Southern Finland (Hyytiälä) and Northern Finland (Värriö), respectively. The analysis also showed that the observed regional NPF events started over the continents but not over the Atlantic Ocean. The first approach showed that although large spatial scale NPF events are frequently observed at several locations simultaneously, they are rarely identical (similar characteristics and temporal variations) due to differences in the initial meteorological and geographical conditions between the stations. The growth of the newly formed particles during large spatial scale events can be followed for more than 30 h where the newly formed aerosol particles end up in the Aitken mode (diameter 25–100 nm) and accumulation mode size ranges (diameter 0.1–1 μm). This study showed clear evidence that regional NPF events can pose a significant source for accumulation mode particles over the Scandinavian continent provided that these findings can be generalized to many of the air masses traveling over the European continent.
  •  
34.
  • Jung, Chang Hoon, et al. (författare)
  • The seasonal characteristics of cloud condensation nuclei (CCN) in the arctic lower troposphere
  • 2018
  • Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 70:1, s. 1-13
  • Tidskriftsartikel (refereegranskat)abstract
    • Cloud Condensation Nuclei (CCN) concentration and aerosol size distributions in the Arctic were collected during the period 2007-2013 at the Zeppelin observatory (78.91 degrees N, 11.89 degrees E, 474 masl). Annual median CCN concentration at a supersaturation (SS) of 0.4% show the ranges of 45 approximate to 81cm(-3). The monthly median CCN number density varied between 17cm(-3) in October 2007 and 198cm(-3) in March, 2008. The CCN spectra parameters C (83cm(-3)) and k (0.23) were derived. In addition, calculated annual median value of hygroscopicity parameter is 0.46 at SS of 0.4%. Particle number concentration of accumulation mode from aerosol size distribution measurements are well correlated with CCN concentration. The CCN to CN>10 nm (particle number concentration larger than 10nm in diameter) ratio shows a maximum during March and minimum during July. The springtime high CCN concentration is attributed to high load of accumulation mode aerosol transported from the mid-latitudes, known as Arctic Haze. CCN concentration remains high also during Arctic summer due to the source of new CCN through particle formation followed by consecutive aerosol growth. Lowest aerosol as well as CCN number densities were observed during Arctic autumn and early winter when aerosol formation in the Arctic and long-range transport into the Arctic are not effective.
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35.
  • Khadir, Théodore, 1996-, et al. (författare)
  • Sink, Source or Something In-Between? Net Effects of Precipitation on Aerosol Particle Populations
  • 2023
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 50:19
  • Tidskriftsartikel (refereegranskat)abstract
    • Interactions between atmospheric aerosols, clouds, and precipitation impact Earth's radiative balance and air quality, yet remain poorly constrained. Precipitating clouds serve as major sinks for particulate matter, but recent studies suggest that precipitation may also act as a particle source. The magnitude of the sources versus sinks, particularly for cloud condensation nuclei (CCN) numbers, remain unquantified. This study analyzes multi-year in situ observations from tropical and boreal forests, as well as Arctic marine environment, showing links between recent precipitation and enhanced particle concentrations, including CCN-sized particles. In some cases, the magnitude of precipitation-related source equals or surpasses corresponding removal effect. Our findings highlight the importance of cloud-processed material in determining near-surface particle concentrations and the value of long-term in situ observations for understanding aerosol particle life cycle. Robust patterns emerge from sufficiently long data series, allowing for quantitative assessment of the large-scale significance of new phenomena observed in case studies.
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36.
  • Koike, M., et al. (författare)
  • Year-Round In Situ Measurements of Arctic Low-Level Clouds : Microphysical Properties and Their Relationships With Aerosols
  • 2019
  • Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 124:3, s. 1798-1822
  • Tidskriftsartikel (refereegranskat)abstract
    • Two years of continuous in situ measurements of Arctic low-level clouds have been made at the Mount Zeppelin Observatory (78 degrees 56N, 11 degrees 53E), in Ny-angstrom lesund, Spitsbergen. The monthly median value of the cloud particle number concentration (N-c) showed a clear seasonal variation: Its maximum appeared in May-July (658cm(-3)), and it remained low between October and March (87cm(-3)). At temperatures warmer than 0 degrees C, a clear correlation was found between the hourly N-c values and the number concentrations of aerosols with dry diameters larger than 70nm (N-70), which are proxies for cloud condensation nuclei (CCN). When clouds were detected at temperatures colder than 0 degrees C, some of the data followed the summertime N-c to N-70 relationship, while other data showed systematically lower N-c values. The lidar-derived depolarization ratios suggested that the former (CCN-controlled) and latter (CCN-uncontrolled) data generally corresponded to clouds consisting of supercooled water droplets and those containing ice particles, respectively. The CCN-controlled data persistently appeared throughout the year at Zeppelin. The aerosol-cloud interaction index (ACI=dlnN(c)/(3dlnN(70))) for the CCN-controlled data showed high sensitivities to aerosols both in the summer (clean air) and winter-spring (Arctic haze) seasons (0.220.03 and 0.250.02, respectively). The air parcel model calculations generally reproduced these values. The threshold diameters of aerosol activation (D-act), which account for the N-c of the CCN-controlled data, were as low as 30-50nm when N-70 was less than 30cm(-3), suggesting that new particle formation can affect Arctic cloud microphysics.
  •  
37.
  • Kulmala, M., et al. (författare)
  • General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales
  • 2011
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:24, s. 13061-13143
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.
  •  
38.
  • Kulmala, Markku, et al. (författare)
  • Overview of the biosphere-aerosol-cloud-climate interactions (BACCI) studies
  • 2008
  • Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60:3, s. 300-317
  • Forskningsöversikt (refereegranskat)abstract
    • Here we present research methods and results obtained by the Nordic Centre of Excellence Biosphere-Aerosol-Cloud-Climate Interactions (BACCI) between 1 January 2003 and 31 December 2007. The centre formed an integrated attempt to understand multiple, but interlinked, biosphere-atmosphere interactions applying inter and multidisciplinary approaches in a coherent manner. The main objective was to study the life cycle of aerosol particles and their importance on climate change. The foundation in BACCI was a thorough understanding of physical, meteorological, chemical and ecophysiological processes, providing a unique possibility to study biosphere-aerosol-cloud-climate interactions. Continuous measurements of atmospheric concentrations and fluxes of aerosol particles and precursors and, CO2/aerosol trace gas interactions in different field stations (e.g. SMEAR) were supported by models of particle thermodynamics, transport and dynamics, atmospheric chemistry, boundary layer meteorology and forest growth. The main progress was related to atmospheric new particle formation, existence of clusters, composition of nucleation mode aerosol particles, chemical precursors of fresh aerosol particles, the contribution of biogenic aerosol particles on the global aerosol load, transport, transformation and deposition of aerosol particles, thermodynamics related to aerosol particles and cloud droplets, and the microphysics and chemistry of cloud droplet formation.
  •  
39.
  • Laj, Paolo, et al. (författare)
  • A global analysis of climate-relevant aerosol properties retrieved from the network of Global Atmosphere Watch (GAW) near-surface observatories
  • 2020
  • Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 13:8, s. 4353-4392
  • Tidskriftsartikel (refereegranskat)abstract
    • Aerosol particles are essential constituents of the Earth's atmosphere, impacting the earth radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. In contrast to most greenhouse gases, aerosol particles have short atmospheric residence times, resulting in a highly heterogeneous distribution in space and time. There is a clear need to document this variability at regional scale through observations involving, in particular, the in situ near-surface segment of the atmospheric observation system. This paper will provide the widest effort so far to document variability of climate-relevant in situ aerosol properties (namely wavelength dependent particle light scattering and absorption coefficients, particle number concentration and particle number size distribution) from all sites connected to the Global Atmosphere Watch network. High-quality data from almost 90 stations worldwide have been collected and controlled for quality and are reported for a reference year in 2017, providing a very extended and robust view of the variability of these variables worldwide. The range of variability observed worldwide for light scattering and absorption coefficients, single-scattering albedo, and particle number concentration are presented together with preliminary information on their long-term trends and comparison with model simulation for the different stations. The scope of the present paper is also to provide the necessary suite of information, including data provision procedures, quality control and analysis, data policy, and usage of the ground-based aerosol measurement network. It delivers to users of the World Data Centre on Aerosol, the required confidence in data products in the form of a fully characterized value chain, including uncertainty estimation and requirements for contributing to the global climate monitoring system.
  •  
40.
  • Lihavainen, Heikki, et al. (författare)
  • Observational signature of the direct radiative effect by natural boreal forest aerosols and its relation to the corresponding first indirect effect
  • 2009
  • Ingår i: Journal of Geophysical Research. - : American Geophysical Union. - 0148-0227 .- 2156-2202. ; 114
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • By using a screened set of long-term aerosol measurement data, the contribution of natural boreal forest aerosols to the direct radiative effect (DRE) was observed at a remote continental site in northern Finland. Averaged over the summer season, the magnitude of this effect at the top of the atmosphere was estimated to be in the range -(0.37-0.74) W m(-2) in our study region and possibly somewhat higher over the whole boreal forest region. Globally, the DRE owing to boreal forest aerosols is much smaller than that owing to natural sea salt or dust aerosols, as well as direct radiative forcing by anthropogenic aerosols. We also updated the earlier estimates of the first indirect radiative effect (IRE) by natural boreal forest aerosols. We found that this IRE is likely to be substantially higher, perhaps more than an order of magnitude, than the corresponding DRE
  •  
41.
  • Lupi, Angelo, et al. (författare)
  • Multi-seasonal ultrafine aerosol particle number concentration measurements at the Gruvebadet observatory, Ny-lesund, Svalbard Islands
  • 2016
  • Ingår i: Rendiconti lincei scienze fisiche e naturali. - : Springer Science and Business Media LLC. - 2037-4631. ; 27, s. 59-71
  • Tidskriftsartikel (refereegranskat)abstract
    • The object of this study was to investigate the different modal behavior of ultrafine aerosol particles collected at the Gruvebadet observatory located in Ny-lesund (Svalbard Islands, 78A degrees 55'N, 11A degrees 56'E). Aerosol particle size distribution was measured in the size range from 10 to 470 nm typically from the beginning of spring to the beginning of fall during four (non-consecutive) years (2010, 2011, 2013 and 2014). The median concentration for the whole period taken into account was 214 particles cm(-3), oscillating between the median maximum in July with a concentration of 257 particles cm(-3) and a median minimum in April with 197 particles cm(-3). The median total number concentration did not present a well-defined seasonal behavior, as shown by contrast looking at the sub/modal number concentration, where distinct trends appeared in the predominant accumulation concentration recorded during April/May and the preponderant concentration of Aitken particles during the summer months. Lastly, the short side-by-side spring 2013 campaign performed at the Zeppelin observatory with a differential mobility particle sizer was characterized by an aerosol concentration mean steady difference between the two instruments of around 14 %, thereby supporting the reliability of the device located at Gruvebadet.
  •  
42.
  • Matisans, Modris, et al. (författare)
  • New Aerosol Particle Formation in Amazonia
  • 2013
  • Ingår i: NUCLEATION AND ATMOSPHERIC AEROSOLS. - : American Institute of Physics (AIP). - 9780735411524 ; , s. 571-574
  • Konferensbidrag (refereegranskat)abstract
    • Particle nucleation in Amazonia has been an enigma throughout decades of active scrutiny of natural nucleation processes; however, measurements have so far been thought to fail capturing an actual new particle formation (NPF) event. In this study we have analyzed latest measurements of ultra-fine particle size distributions alongside with air ion spectra and revealed a diurnal pattern of ultra-fine particle apparent growth. The revealed growth pattern is preceded by diurnal precipitation probability maxima, and simultaneous abundant ion production as detected by Neutral cluster and Air Ion Spectrometer (NAIS) data. Thus, we claim that by implementing statistical analysis of scanning mobility particle sizer (SMPS) data and combining with independent observations from Neutral cluster and Air Ion Spectrometer (NAIS) we can observe a consistent signal of NPF events in Amazonia.
  •  
43.
  • Moroni, B., et al. (författare)
  • Individual Particle Characteristics, Optical Properties and Evolution of an Extreme Long-Range Transported Biomass Burning Event in the European Arctic (Ny-angstrom lesund, Svalbard Islands)
  • 2020
  • Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 125:5
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper reports an exceptional biomass burning (BB) advection event from Alaska registered at Ny‐Ålesund from 10 to 17 July 2015 with particular interest on the influence of the airborne particle characteristics on the optical properties of the aerosol during the event. To this purpose we considered two DEKATI 12‐stage aerosol samples spanning the entire advection and analyzed them by scanning electron microscopy techniques. Aerosol chemical data and microphysical properties were also evaluated in order to correlate any change of individual particle characteristics with the bulk properties of the aerosol. The results of individual particle analysis depict a complex event characterized by a first phase (P1) of massive input of BB carbonaceous particles (i.e., tar balls, popcorn refractory particles, and organic particles), and by a second phase (P2) dominated by inorganic salts. The peculiar feature of this BB event is the exceptionally large grain size of the subspherical organic particles at the beginning of the event with respect to the background. At these conditions a significant increase of the scattering efficiency may occur even for a small increase of the size parameter. Results of the simulation of the complex refractive indices (n‐ik) confirm this evaluation. Aerosol evolution during the event resulted from the combination of three distinct occurrences: (a) progressive rotation of air mass circulation toward non‐BB source areas, (b) development of a thick fog layer in the planetary boundary layer, and (c) sea salt spray direct advection of local/regional provenance.
  •  
44.
  • Mårtensson, E. Monica, et al. (författare)
  • The role of sea-salt emissions in controlling the marine Aitken and accumulation mode aerosol : a model study
  • 2010
  • Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 62:4, s. 259-279
  • Tidskriftsartikel (refereegranskat)abstract
    • The remote marine aerosol and the cloud droplet number concentration (CDNC) are examined with an aerosol microphysics box model in an attempt to better understand the processes involved in the formation and transformation of the marine aerosol. Emission of submicrometre sea-salt and dimethylsulfide (DMS) have been included together with aerosol dynamics, gas and liquid phase chemistry and cloud processing representative for the marine boundary layer atmosphere. Our simulations are able to reproduce a bimodal submicrometre size distribution with realistic number concentrations even when new particle formation by nucleation is neglected. This indicates that ultrafine primary sea-salt flux is an important source of Aitken mode particles and CDNC. However, sulphate still constitutes 20-80% of the Aitken and accumulation mode masses. The temperature dependence of the sea-salt source function leads to a 23% decrease in total number concentration when the temperature increases from 12 to 20 degrees C. The influence of DMS emission on the aerosol and CDNC is minimal but the size distribution and mass concentration of sulphate is changed, mostly due to in-cloud processes. The wind speed is the dominant factor determining the CDNC, although entrainment of aerosols from free troposphere can have a substantial effect.
  •  
45.
  •  
46.
  • Nieminen, Tuomo, et al. (författare)
  • Global analysis of continental boundary layer new particle formation based on long-term measurements
  • 2018
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:19, s. 14737-14756
  • Tidskriftsartikel (refereegranskat)abstract
    • Atmospheric new particle formation (NPF) is an important phenomenon in terms of global particle number concentrations. Here we investigated the frequency of NPF, formation rates of 10 nm particles, and growth rates in the size range of 10-25 nm using at least 1 year of aerosol number size-distribution observations at 36 different locations around the world. The majority of these measurement sites are in the Northern Hemisphere. We found that the NPF frequency has a strong seasonal variability. At the measurement sites analyzed in this study, NPF occurs most frequently in March-May (on about 30 % of the days) and least frequently in December-February (about 10 % of the days). The median formation rate of 10 nm particles varies by about 3 orders of magnitude (0.01-10 cm(-3) s(-1)) and the growth rate by about an order of magnitude (1-10 nm h(-1)). The smallest values of both formation and growth rates were observed at polar sites and the largest ones in urban environments or anthropogenically influenced rural sites. The correlation between the NPF event frequency and the particle formation and growth rate was at best moderate among the different measurement sites, as well as among the sites belonging to a certain environmental regime. For a better understanding of atmospheric NPF and its regional importance, we would need more observational data from different urban areas in practically all parts of the world, from additional remote and rural locations in North America, Asia, and most of the Southern Hemisphere (especially Australia), from polar areas, and from at least a few locations over the oceans.
  •  
47.
  • Ohata, Sho, et al. (författare)
  • Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic
  • 2021
  • Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 14:10, s. 6723-6748
  • Tidskriftsartikel (refereegranskat)abstract
    • Long-term measurements of atmospheric mass concentrations of black carbon (BC) are needed to investigate changes in its emission, transport, and deposition. However, depending on instrumentation, parameters related to BC such as aerosol absorption coefficient (babs) have been measured instead. Most ground-based measurements of babs in the Arctic have been made by filter-based absorption photometers, including particle soot absorption photometers (PSAPs), continuous light absorption photometers (CLAPs), Aethalometers, and multi-angle absorption photometers (MAAPs). The measured babs can be converted to mass concentrations of BC (MBC) by assuming the value of the mass absorption cross section (MAC; MBC= babs/ MAC). However, the accuracy of conversion of babs to MBC has not been adequately assessed. Here, we introduce a systematic method for deriving MAC values from babs measured by these instruments and independently measured MBC. In this method, MBC was measured with a filter-based absorption photometer with a heated inlet (COSMOS). COSMOS-derived MBC (MBC (COSMOS)) is traceable to a rigorously calibrated single particle soot photometer (SP2), and the absolute accuracy of MBC (COSMOS) has been demonstrated previously to be about 15 % in Asia and the Arctic. The necessary conditions for application of this method are a high correlation of the measured babs with independently measured MBC and long-term stability of the regression slope, which is denoted as MACcor (MAC derived from the correlation). In general, babs–MBC (COSMOS) correlations were high (r2= 0.76–0.95 for hourly data) at Alert in Canada, Ny-Ålesund in Svalbard, Barrow (NOAA Barrow Observatory) in Alaska, Pallastunturi in Finland, and Fukue in Japan and stable for up to 10 years. We successfully estimated MACcor values (10.8–15.1 m2 g−1 at a wavelength of 550 nm for hourly data) for these instruments, and these MACcor values can be used to obtain error-constrained estimates of MBC from babs measured at these sites even in the past, when COSMOS measurements were not made. Because the absolute values of MBC at these Arctic sites estimated by this method are consistent with each other, they are applicable to the study of spatial and temporal variation in MBC in the Arctic and to evaluation of the performance of numerical model calculations.
  •  
48.
  • Pandolfi, Marco, et al. (författare)
  • A European aerosol phenomenology-6 : scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
  • 2018
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:11, s. 7877-7911
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (sigma(sp)) and hemispheric backscattering (sigma(bsp)) coefficients, scattering Angstrom exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of sigma(sp) is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, sigma(sp) also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intraannual variability. At mountain sites, higher sigma(sp) and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher sigma(sp) values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low sigma(sp) values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high sigma(sp) values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of sigma(sp) are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of sigma(sp) are consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.
  •  
49.
  • Park, Ki-Tae, et al. (författare)
  • Dimethyl Sulfide-Induced Increase in Cloud Condensation Nuclei in the Arctic Atmosphere
  • 2021
  • Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 35:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Oceanic dimethyl sulfide (DMS) emissions have been recognized as a biological regulator of climate by contributing to cloud formation. Despite decades of research, the climatic role of DMS remains ambiguous largely because of limited observational evidence for DMS-induced cloud condensation nuclei (CCN) enhancement. Here, we report concurrent measurement of DMS, physiochemical properties of aerosol particles, and CCN in the Arctic atmosphere during the phytoplankton bloom period of 2010. We encountered multiple episodes of new particle formation (NPF) and particle growth when DMS mixing ratios were both low and high. The growth of particles to sizes at which they can act as CCN accelerated in response to an increase in atmospheric DMS. Explicitly, the sequential increase in all relevant parameters (including the source rate of condensable vapor, the growth rate of particles, Aitken mode particles, hygroscopicity, and CCN) was pronounced at the DMS-derived NPF and particle growth events. This field study unequivocally demonstrates the previously unconfirmed roles of DMS in the growth of particles into climate-relevant size and eventual CCN activation.
  •  
50.
  • Partridge, Daniel, 1984-, et al. (författare)
  • A study of marine stratocumulus clouds using an inverse modelling approach
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • This paper presents a Bayesian inverse modelling approach to simultaneously assess the ability of a pseudo-adiabatic cloud parcel model to match in-situ measurements of the droplet size distribution in a cloud as well as model parameters describing the updraft and different aerosol microphysical properties (herein termed calibration parameters). Our methodology is tested using observations from two clean (average accumulation mode number concentration < 60 cm-3) and two polluted clouds (average accumulation mode number concentration > 100 cm-3) observed during the Marine Stratus/Stratocumulus Experiment (MASE II) campaign. Our framework capitalizes on recent developments in Markov Chain Monte Carlo (MCMC) simulation and retrieves the most likely parameter values and their underlying posterior probability density function. This distribution provides necessary information to efficiently and in a statistically robust manner, assess both the global sensitivity of aerosol physiochemical and meteorological parameters, and the suitability of cloud parcel models to comprehensively describe the evolution of cloud droplet size distributions in stratocumulus clouds. We demonstrate that the updraft velocity is the most important calibration parameter for describing the observed droplet distribution for each cloud case, corroborating previous findings. The accumulation mode number, shape and size are found to be more important than chemistry except for the most polluted conditions (average accumulation mode number concentration ~455 cm-3). This highlights that conditions exist for marine stratocumulus clouds in which an accurate description of the aerosol chemistry is a pre-requisite for the accurate representation of cloud microphysical properties. Overall, the MCMC algorithm successfully matches the observed droplet size distribution for each cloud case. In doing so, however, the subsequent agreement between the derived and measured calibration parameters is generally poor. An important result from this analysis is that for certain calibration parameters, consistent patterns of deviation were found in the posterior distributions for all the clouds included in this study. This finding indicates that either there is systematic sampling or averaging artefacts in our observations, or our pseudo-adiabatic cloud parcel model omits or consistently misrepresents processes and/or parameter(s) required to accurately simulate the droplet size distributions of the observed marine stratocumulus. By repeating our inverse methodology with more calibration parameters of which current measurements are uncertain (surface tension, mass accommodation coefficient), we find that it is likely that the process description within the current formulation of the pseudo-adiabatic cloud model used in this study misses a dynamical process rather than parameter(s).
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