| 1. |
- Drewnick, Frank, et al.
(författare)
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Measurement of ambient, interstitial, and residual aerosol particles on a mountaintop site in central Sweden using an aerosol mass spectrometer and a CVI
- 2007
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Ingår i: Journal of Atmospheric Chemistry. - : Springer Science and Business Media LLC. - 0167-7764 .- 1573-0662. ; 56:1, s. 1-20
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Tidskriftsartikel (refereegranskat)abstract
- The Aerodyne aerosol mass spectrometer (Q-AMS) was coupled with a counterflow virtual impactor (CVI) for the first time to measure cloud droplet residuals of warm tropospheric clouds on Mt. Areskutan in central Sweden in July 2003. Operating the CVI in different operational modes generated mass concentration and species-resolved mass distribution data for non-refractory species of the ambient, interstitial, and residual aerosol. The ambient aerosol measurements revealed that the aerosol at the site was mainly influenced by long-range transport and regional photochemical generation of nitrate and organic aerosol components. Four different major air masses were identified for the time interval of the experiment. While two air masses that approached the site from northeastern Europe via Finland showed very similar aerosol composition, the other two air masses from polar regions and the British Islands had a significantly different composition. During cloud events the larger aerosol particles were found to be activated into cloud droplets. On a mass basis the activation cut-off diameter was approximately 150 nm for nitrate and organics dominated particles and 200 nm for sulfate dominated particles. Generally nitrate and organics were found to be activated into cloud droplets with higher efficiency than sulfate. While a significant fraction of the nitrate in ambient particles was organic nitrates or nitrogen-containing organic species, the nitrate found in the cloud droplet residuals was mainly ammonium nitrate. After passage of clouds the ambient aerosol size distribution had shifted to smaller particle sizes due to the predominantly activation of larger aerosol particles without a significant change in the relative composition of the ambient aerosol.
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| 2. |
- Glantz, Paul, et al.
(författare)
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Trends in MODIS and AERONET derived aerosol optical thickness over Northern Europe
- 2019
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 71:1
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Tidskriftsartikel (refereegranskat)abstract
- Long-term Aqua and Terra MODIS (MODerate resolution Imaging Spectroradiometer) Collections 5.1 and 6.1 (c051 and c061, respectively) aerosol data have been combined with AERONET (AERosol RObotic NETwork) ground-based sun photometer observations to examine trends in aerosol optical thickness (AOT, at 550nm) over Northern Europe for the months April to September. For the 1927 and 1559 daily coincident measurements that were obtained for c051 and c061, respectively, MODIS AOT varied by 86 and 90%, respectively, within the predicted uncertainty of one standard deviation of the retrieval over land (AOT = +/- 0.05 +/- 0.15AOT). For the coastal AERONET site Gustav Dalen Tower (GDT), Sweden, larger deviations were found for MODIS c051 and c061 (79% and 75%, respectively, within predicted uncertainty). The Baltic Sea provides substantially better statistical representation of AOT than the surrounding land areas and therefore favours the investigations of trends in AOT over the region. Negative trends of 1.5% and 1.2% per year in AOT, based on daily averaging, were found for the southwestern Baltic Sea from MODIS c051 and c061, respectively. This is in line with a decrease of 1.2% per year in AOT at the AERONET station Hamburg. For the western Gotland Basin area, Sweden, negative trends of 1.5%, 1.1% and 1.6% per year in AOT have been found for MODIS c051, MODIS c061 and AERONET GDT, respectively. The strongest trend of -1.8% per year in AOT was found for AERONET Belsk, Poland, which can be compared to -1.5% per day obtained from MODIS c051 over central Poland. The trends in MODIS and AERONET AOT are nearly all statistically significant at the 95% confidence level. The strongest aerosol sources are suggested to be located southwest, south and southeast of the investigation area, although the highest prevalence of pollution events is associated with air mass transport from southwest.
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| 3. |
- Glantz, Paul, et al.
(författare)
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Unmasking the Effects of Aerosols on Greenhouse Warming Over Europe
- 2022
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 127:22
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Tidskriftsartikel (refereegranskat)abstract
- Aerosol optical thickness (AOT) has decreased substantially in Europe in the summer half year (April–September) since 1980, with almost a 50% reduction in Central and Eastern Europe, according to Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) reanalysis. At the same time, strong positive trends in ERA5 reanalysis surface solar radiation downward for all-sky and clear-sky conditions (SSRD and SSRDc, respectively) and temperature at 2 m are found for Europe in summer during the period 1979–2020. The GEBA observations show as well strong increases in SSRD during the latest four decades. Estimations of changes in SSRDc, using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model, show similarly strong increases when fed by MERRA-2 AOT. The estimates of warming in this study, caused by increases in SSRD and SSRDc, are based on energy budget approximations and the Stefan Boltzmann law. The increases in near surface temperature, estimated both for clear-sky and all-sky conditions, are up to about 1°C for Central and Eastern Europe. The total warming over large parts of this region for clear-sky conditions is however nearly double the global mean temperature increase of 1.1°C, while somewhat less for all-sky conditions. The effects of aerosols on warming over the southerly Iberian Peninsula are weaker compared to countries further north. The rapid total warming over the Iberian Peninsula is probably caused by greenhouse warming, drier surface conditions, and to some degree decline in aerosols. Reduced cloud cover is found for large parts of Europe in summer during the latest four decades.
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| 4. |
- Gonzalez, N. J. D., et al.
(författare)
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Primary and secondary organics in the tropical Amazonian rainforest aerosols : chiral analysis of 2-methyltetraols
- 2014
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Ingår i: ENVIRON SCI-PROC IMP. - : Royal Society of Chemistry (RSC). - 2050-7887 .- 2050-7895. ; 16:6, s. 1413-1421
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the application of a new method to facilitate the distinction between biologically produced (primary) and atmospherically produced (secondary) organic compounds in ambient aerosols based on their chirality. The compounds chosen for this analysis were the stereomers of 2-methyltetraols, (2R, 3S)- and (2S, 3R)-methylerythritol, (L- and D-form, respectively), and (2S, 3S)- and (2R, 3R)-methylthreitol (L- and D-form), shown previously to display some enantiomeric excesses in atmospheric aerosols, thus to have at least a partial biological origin. In this work PM10 aerosol fractions were collected in a remote tropical rainforest environment near Manaus, Brazil, between June 2008 and June 2009 and analysed. Both 2-methylerythritol and 2-methylthreitol displayed a net excess of one enantiomer (either the L- or the D-form) in 60 to 72% of these samples. These net enantiomeric excesses corresponded to compounds entirely biological but accounted for only about 5% of the total 2-methyltetrol mass in all the samples. Further analysis showed that, in addition, a large mass of the racemic fractions (equal mixtures of D- and L-forms) was also biological. Estimating the contribution of secondary reactions from the isomeric ratios measured in the samples (=ratios 2-methylthreitol over 2-methylerythritol), the mass fraction of secondary methyltetrols in these samples was estimated to a maximum of 31% and their primary fraction to a minimum of 69%. Such large primary fractions could have been expected in PM10 aerosols, largely influenced by biological emissions, and would now need to be investigated in finer aerosols. This work demonstrates the effectiveness of chiral and isomeric analyses as the first direct tool to assess the primary and secondary fractions of organic aerosols.
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| 5. |
- Karlsson, Nélida Jocelyn Donají, 1980-
(författare)
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Primary and secondary organics in biogenic atmospheric aerosol : The chiral study of 2-methyltetrols from method development to application
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Distinguishing between the primary and secondary origin of the organic components in atmospheric aerosols is one of the key parameters in assessing the relevance and role of different chemical species in the overall chemistry of the atmosphere. Currently available methods used in field measurements are not able to fully discriminate between the primary or secondary origin of compounds detected in atmospheric aerosols. This thesis presents a new analytical method for examining the primary and secondary origin of certain organic constituents, 2-methyltetrols, in biogenic atmospheric aerosol based on chirality. Chirality is a molecular structure property that makes a pair of compounds to be mirror images of each other. Consequently, compounds with chirality represent challenges for their study as individual species. This is of importance because 2-methyltetrols have been studied so far solely as two diastereomeric constituents, 2-methylerythritol and 2-methylthreitol, when in reality they are four different compounds: (2R,3S)-methylerythritol, (2S,3R)-methylerythritol, (2S,3S)-methylthreitol and (2R,3R)-mehtylthreitol. Furthermore, 2-methylerythritol and 2-methylthreitol are currently used as the main tracers for the contribution of isoprene to the formation of secondary organic aerosols in the atmosphere. Therefore, a new method directed to the chiral analysis of 2-methyltetrols was developed and applied to atmospheric samples collected at Aspvreten, Sweden, the Amazon, Brazil, and Hyytiälä, Finland. The results indicate that 2-methyltetrols in samples from the three sites have both primary and secondary origins with variability among sites as well as seasons. The estimates of the minimum primary origin contribution represent a significant fraction of the total mass of 2-methyltetrols in the samples. In some samples the contribution was as high as 30% of the total mass of these compounds. Even though 2-methyltetrols have secondary origin, their use as tracers for the atmospheric oxidation of isoprene should be discouraged, unless relative primary contributions are considered, as this study has demonstrated that they have primary origin as well. Moreover, the development and application of chiral analytical methods should be prioritized in order to improve the prevailing understanding of the real chemical composition and origin of chiral compounds in atmospheric aerosols.
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| 6. |
- Leung, Wing -Y. H., et al.
(författare)
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Sensitivity of a continental night-time stratocumulus-topped boundary layer to varying environmental conditions
- 2016
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Ingår i: Quarterly Journal of the Royal Meteorological Society. - : Wiley. - 0035-9009 .- 1477-870X. ; 142:700, s. 2911-2924
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Tidskriftsartikel (refereegranskat)abstract
- Large-eddy simulation of a nocturnal stratocumulus-topped boundary layer in a continental midlatitude environment has been performed to examine the sensitivity of the cloud to a number of different environmental parameters. The simulations showed that the stratocumulus cloud was strongly affected by the presence of an overlying free tropospheric cirrus cloud (FTC), in agreement with previous studies of marine nighttime stratocumulus. When introducing an FTC with an optical thickness of 2, stratocumulus liquid water path decreased by 30%. Enhancing the optical thickness of the FTC to 8 further decreased the liquid water path by almost 10%. The presence of an FTC decreased the cloud-top radiative cooling which decreased the turbulent mixing in the boundary layer, so that the liquid water content and cloud depth were reduced. The sensitivity of the stratocumulus cloud to an overlying FTC was found to be affected by the moisture content in the free troposphere. When a clear positive or negative moisture gradient above the inversion was imposed, and an overlying FTC with an optical thickness of 8 was introduced, the stratocumulus cloud LWP decreased by more than 40%. Furthermore, the effect of changes in free tropospheric moisture content and an overlying FTC on the stratocumulus cloud properties was found to be nonlinear; the combined response was in general weaker than the two responses added together. The modeled response to changes in cloud condensation nuclei (CCN) concentrations was found to be non-significant, unless the CCN concentrations were so low that drizzle was induced (similar to 50 cm(-3))
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| 7. |
- Martinsson, Bengt G., et al.
(författare)
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Elemental composition of fog interstitial particle size fractions and hydrophobic fractions related to fog droplet nucleation scavenging
- 1992
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509. ; 44:5, s. 593-603
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Tidskriftsartikel (refereegranskat)abstract
- The cloud nucleation scavenging process was studied during a joint campaign of the EUROTRAC sub‐project Ground‐based Cloud Experiment. It was found that the particle size has a strong influence on the partitioning of particles between the cloud droplet and the interstitial aerosol reservoirs. A new aerosol sampling unit, the relative humidity processing system, was employed for the extraction of particles with a low growth‐ability with respect to increased relative humidity. The system supplied tracer elements on the particle growth‐ability. These elements could be used to identify a factor related to particle hygroscopic properties, which was in effect as a selector of cloud condensation nuclei.
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| 8. |
- Modini, R. L., et al.
(författare)
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Primary marine aerosol-cloud interactions off the coast of California
- 2015
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 120:9, s. 4282-4303
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Tidskriftsartikel (refereegranskat)abstract
- Primary marine aerosol (PMA)-cloud interactions off the coast of California were investigated using observations of marine aerosol, cloud condensation nuclei (CCN), and stratocumulus clouds during the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) studies. Based on recently reported measurements of PMA size distributions, a constrained lognormal-mode-fitting procedure was devised to isolate PMA number size distributions from total aerosol size distributions and applied to E-PEACE measurements. During the 12 day E-PEACE cruise on the R/V Point Sur, PMA typically contributed less than 15% of total particle concentrations. PMA number concentrations averaged 12 cm(-3) during a relatively calmer period (average wind speed 12m/s(1)) lasting 8 days, and 71cm(-3) during a period of higher wind speeds (average 16m/s(1)) lasting 5 days. On average, PMA contributed less than 10% of total CCN at supersaturations up to 0.9% during the calmer period; however, during the higher wind speed period, PMA comprised 5-63% of CCN (average 16-28%) at supersaturations less than 0.3%. Sea salt was measured directly in the dried residuals of cloud droplets during the SOLEDAD study. The mass fractions of sea salt in the residuals averaged 12 to 24% during three cloud events. Comparing the marine stratocumulus clouds sampled in the two campaigns, measured peak supersaturations were 0.20.04% during E-PEACE and 0.05-0.1% during SOLEDAD. The available measurements show that cloud droplet number concentrations increased with >100 nm particles in E-PEACE but decreased in the three SOLEDAD cloud events.
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| 9. |
- Niemi, Maria, et al.
(författare)
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Lockdown Measures Which Reduced Greenhouse Gas Emissions With Little Negative Impact on Quality of Life
- 2021
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Ingår i: Earth's Future. - 2328-4277. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- Lockdown measures in response to the new Covid-19 virus have caused the largest ever fall of annual greenhouse gas emissions. A key question that we attempt to answer in this study is which, if any, of these measures can be productively encouraged post-lockdown in efforts to sustain at least part of this reduction in emissions. Sweden is uniquely suited for our study because the voluntary nature of lockdown in Sweden allowed us to assess the level of compliance to recommendations and its effects on greenhouse gas emissions. First, we assessed the change of perceived quality of life (QOL) among 746 individuals from Stockholm region due to adhering to lockdown measures. Second, we calculated the associated change of annual per capita greenhouse emissions. We found that avoiding travel for work, avoiding purchasing, and avoiding restaurants had the least negative effect on QOL, and at the same time the largest positive effect on carbon dioxide equivalent (CO(2)e) emission reductions. We conclude that these are potential leverage points for stimulating behavioral change that has a positive climatic impact.
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| 10. |
- Nobre, Carlos, et al.
(författare)
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ADDRESSING THE COMPLEXITY OF THE EARTH SYSTEM
- 2010
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - 0003-0007 .- 1520-0477. ; 91:10, s. 1389-1396
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Tidskriftsartikel (refereegranskat)
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