| 1. |
- Gramlich, Yvette, 1993-, et al.
(författare)
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Revealing the chemical characteristics of Arctic low-level cloud residuals – in situ observations from a mountain site
- 2023
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Ingår i: Atmospheric Chemistry And Physics. - 1680-7316 .- 1680-7324. ; 23:12, s. 6813-6834
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Tidskriftsartikel (refereegranskat)abstract
- The role aerosol chemical composition plays in Arctic low-level cloud formation is still poorly understood. In this study we address this issue by combining in situ observations of the chemical characteristics of cloud residuals (dried liquid cloud droplets or ice crystals) and aerosol particles from the Zeppelin Observatory in Ny-Ålesund, Svalbard (approx. 480 m a.s.l.). These measurements were part of the 1-year-long Ny-Ålesund Aerosol and Cloud Experiment 2019–2020 (NASCENT). To obtain the chemical composition of cloud residuals at molecular level, we deployed a Filter Inlet for Gases and AEROsols coupled to a Chemical Ionization Mass Spectrometer (FIGAERO-CIMS) with iodide as the reagent ion behind a ground-based counterflow virtual impactor (GCVI). The station was enshrouded in clouds roughly 15 % of the time during NASCENT, out of which we analyzed 14 cloud events between December 2019 and December 2020. During the entire year, the composition of the cloud residuals shows contributions from oxygenated organic compounds, including organonitrates, and traces of the biomass burning tracer levoglucosan. In summer, methanesulfonic acid (MSA), an oxidation product of dimethyl sulfide (DMS), shows large contributions to the sampled mass, indicating marine natural sources of cloud condensation nuclei (CCN) and ice nucleating particle (INP) mass during the sunlit part of the year. In addition, we also find contributions of the inorganic acids nitric acid and sulfuric acid, with outstanding high absolute signals of sulfuric acid in one cloud residual sample in spring and one in late summer (21 May and 12 September 2020), probably caused by high anthropogenic sulfur emissions near the Barents Sea and Kara Sea. During one particular cloud event, on 18 May 2020, the air mass origin did not change before, during, or after the cloud. We therefore chose it as a case study to investigate cloud impact on aerosol physicochemical properties. We show that the overall chemical composition of the organic aerosol particles was similar before, during, and after the cloud, indicating that the particles had already undergone one or several cycles of cloud processing before being measured as residuals at the Zeppelin Observatory and/or that, on the timescales of the observed cloud event, cloud processing of the organic fraction can be neglected. Meanwhile, there were on average fewer particles but relatively more in the accumulation mode after the cloud. Comparing the signals of sulfur-containing compounds of cloud residuals with aerosols during cloud-free conditions, we find that sulfuric acid had a higher relative contribution to the cloud residuals than to aerosols during cloud-free conditions, but we did not observe an increase in particulate MSA due to the cloud. Overall, the chemical composition, especially of the organic fraction of the Arctic cloud residuals, reflected the overall composition of the general aerosol population well. Our results thus suggest that most aerosols can serve as seeds for low-level clouds in the Arctic.
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| 2. |
- Pereira Freitas, Gabriel, 1993-, et al.
(författare)
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Contribution of primary biological aerosol particles to low-level Arctic cloud condensation nuclei
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Mixed-phase clouds (MPC) are key players in the Arctic climate system due to their role in modulating solar and terrestrial radiation. Such radiative interactions critically rely on the ice content of MPC which, in turn, partly depends on the availability of ice nucleating particles (INP). INP sources and concentrations are poorly understood in the Arctic. Recently, INP active at high temperatures were linked to be primary biological aerosol particles (PBAP). Here, we investigated for a full year the PBAP abundance and variability within cloud residuals, directly sampled by a multiparameter bioaerosol spectrometer coupled to a ground-based counterflow virtual impactor inlet at the Zeppelin Observatory (475 m asl), Ny-Ålesund, Svalbard. PBAP concentrations (10−3–10−2L−1) and contributions to coarse-mode aerosol (1 in every 103–104) within cloud residuals were found to be close to those expected for concentrations of high-temperature INP. Transmission electron microscopy also confirmed the presence of PBAP, most likely bacteria, within the cloud residual samples. Seasonally, our results reveal an elevated presence of PBAP within cloud residuals during the summer. Parallel water vapor isotope measurements points towards a link between summer clouds and regionally sourced air masses. Low-level MPC were predominantly observed at the beginning and end of summer, and one explanation for their presence is the existence of high-temperature INP. In this study, we present observational evidence that PBAP might play a role in determining the phase of low-level Arctic clouds, with potential implications for the Arctic climate given ongoing changes in the hydrological and biogeochemical cycles that influence the PBAP flux in and towards the Arctic.
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| 3. |
- Pereira Freitas, Gabriel, 1993-, et al.
(författare)
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Regionally sourced bioaerosols drive high-temperature ice nucleating particles in the Arctic
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Primary biological aerosol particles (PBAP) play an important role in the climate system, facilitating the formation of ice within clouds, consequently PBAP may be important in understanding the rapidly changing Arctic. Within this work, we use single-particle fluorescence spectroscopy to identify and quantify PBAP at an Arctic mountain site, with transmission electronic microscopy analysis supporting the presence of PBAP. We find that PBAP concentrations range between 10−3–10−1 L−1 and peak in summer. Evidences suggest that the terrestrial Arctic biosphere is an important regional source of PBAP, given the high correlation to air temperature, surface albedo, surface vegetation and PBAP tracers. PBAP clearly correlate with high-temperature ice nucleating particles (INP) (>-15 °C), of which a high a fraction (>90%) are proteinaceous in summer, implying biological origin. These findings will contribute to an improved understanding of sources and characteristics of Arctic PBAP and their links to INP.
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| 4. |
- Adachi, Kouji, et al.
(författare)
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Composition and mixing state of Arctic aerosol and cloud residual particles from long-term sinale-particle observations at Zeppelin Observatory, Svalbard
- 2022
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:21, s. 14421-14439
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic region is sensitive to climate change and is warming faster than the global average. Aerosol particles change cloud properties by acting as cloud condensation nuclei and ice-nucleating particles, thus influencing the Arctic climate system. Therefore, understanding the aerosol particle properties in the Arctic is needed to interpret and simulate their influences on climate. In this study, we collected ambient aerosol particles using whole-air and PM10 inlets and residual particles of cloud droplets and ice crystals from Arctic low-level clouds (typically, all-liquid or mixed-phase clouds) using a counterflow virtual impactor inlet at the Zeppelin Observatory near Ny-Ålesund, Svalbard, within a time frame of 4 years. We measured the composition and mixing state of individual fine-mode particles in 239 samples using transmission electron microscopy. On the basis of their composition, the aerosol and cloud residual particles were classified as mineral dust, sea salt, K-bearing, sulfate, and carbonaceous particles. The number fraction of aerosol particles showed seasonal changes, with sulfate dominating in summer and sea salt increasing in winter. There was no measurable difference in the fractions between ambient aerosol and cloud residual particles collected at ambient temperatures above 0 ∘C. On the other hand, cloud residual samples collected at ambient temperatures below 0 ∘C had several times more sea salt and mineral dust particles and fewer sulfates than ambient aerosol samples, suggesting that sea spray and mineral dust particles may influence the formation of cloud particles in Arctic mixed-phase clouds. We also found that 43 % of mineral dust particles from cloud residual samples were mixed with sea salt, whereas only 18 % of mineral dust particles in ambient aerosol samples were mixed with sea salt. This study highlights the variety in aerosol compositions and mixing states that influence or are influenced by aerosol–cloud interactions in Arctic low-level clouds.
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| 5. |
- Motos, Ghislain, et al.
(författare)
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Aerosol and dynamical contributions to cloud droplet formation in Arctic low-level clouds
- 2023
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Ingår i: Atmospheric Chemistry And Physics. - 1680-7316 .- 1680-7324. ; 23:21, s. 13941-13956
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic is one of the most rapidly warming regions of the globe. Low-level clouds and fog modify the energy transfer from and to space and play a key role in the observed strong Arctic surface warming, a phenomenon commonly termed “Arctic amplification”. The response of low-level clouds to changing aerosol characteristics throughout the year is therefore an important driver of Arctic change that currently lacks sufficient constraints. As such, during the NASCENT campaign (Ny-Ålesund AeroSol Cloud ExperimeNT) extending over a full year from October 2019 to October 2020, microphysical properties of aerosols and clouds were studied at the Zeppelin station (475 m a.s.l.), Ny-Ålesund, Svalbard, Norway. Particle number size distributions obtained from differential mobility particle sizers as well as chemical composition derived from filter samples and an aerosol chemical speciation monitor were analyzed together with meteorological data, in particular vertical wind velocity. The results were used as input to a state-of-the-art cloud droplet formation parameterization to investigate the particle sizes that can activate to cloud droplets, the levels of supersaturation that can develop, the droplet susceptibility to aerosol and the role of vertical velocity. We evaluate the parameterization and the droplet numbers calculated through a droplet closure with in-cloud in situ measurements taken during nine flights over 4 d. A remarkable finding is that, for the clouds sampled in situ, closure is successful in mixed-phase cloud conditions regardless of the cloud glaciation fraction. This suggests that ice production through ice–ice collisions or droplet shattering may have explained the high ice fraction, as opposed to rime splintering that would have significantly reduced the cloud droplet number below levels predicted by warm-cloud activation theory. We also show that pristine-like conditions during fall led to clouds that formed over an aerosol-limited regime, with high levels of supersaturation (generally around 1 %, although highly variable) that activate particles smaller than 20 nm in diameter. Clouds formed in the same regime in late spring and summer, but aerosol activation diameters were much larger due to lower cloud supersaturations (ca. 0.5 %) that develop because of higher aerosol concentrations and lower vertical velocities. The contribution of new particle formation to cloud formation was therefore strongly limited, at least until these newly formed particles started growing. However, clouds forming during the Arctic haze period (winter and early spring) can be limited by updraft velocity, although rarely, with supersaturation levels dropping below 0.1 % and generally activating larger particles (20 to 200 nm), including pollution transported over a long range. The relationship between updraft velocity and the limiting cloud droplet number agrees with previous observations of various types of clouds worldwide, which supports the universality of this relationship.
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| 6. |
- Pereira Freitas, Gabriel, 1993-
(författare)
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Bioaerosols and their importance for low-level Arctic clouds
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bioaerosols are microorganisms or functional parts of them or other biological matter suspended in air. Examples are bacteria, viruses, pollen, spores, or smaller plant debris. In the atmosphere, bioaerosols can play various functional roles, such as facilitating the spread of genetic material. Moreover, they can play an important role in climate by serving as ice nucleating particles and thus participating in cloud formation. Bioaerosols might play a significant role in a changing Arctic, where aerosol concentrations can be very low, and where natural as well as anthropogenic aerosol sources are subject to drastic changes due to climate change. In the Arctic, aerosols and clouds are prominent actors in climate by mediating short- and long-wave radiation interactions, which are further complicated by the presence of high-albedo surfaces such as sea ice. Thus, constraining the sources of aerosols and their interaction with clouds is key to understanding the Arctic climate and the changes it has been and will undergo.In this work, we used a single-particle instrument to differentiate bioaerosols from other particles on the basis of their fluorescence and light-scattering signal. In the Baltic Sea, we found that bioaerosols are at least 1 in every 104 coarse particles emitted by sea spray. Their temporal emission pattern was not directly correlated with biological tracers, such as chlorophyll; instead, their emission was modulated by the transition between different water masses.The same technique was then applied to a one-year measurement campaign at an Arctic mountain top observatory as part of a greater aerosol-cloud interaction campaign. The recorded seasonal cycle of bioaerosol concentrations peaked in summer and was most likely related to regional terrestrial sources, as its appearance coincided with a decrease in snow cover and an increase in vegetation activity. Moreover, bioaerosols were found to drive the concentration of high-temperature ice nucleating particles, even in winter. In the third study, the importance of bioaerosols serving as cloud seeds was investigated by directly measuring the concentration of bioaerosols within cloud residuals.The presented findings help to elucidate the contribution of bioaerosols to coarse-mode particles for marine and Arctic environments, while also providing a direct link between bioaerosols and clouds. Furthermore, we also provide the first direct observations of bioaerosols involved in cloud formation in the Arctic, along with their possible contribution to the prevalence of mixed-phase clouds in the beginning and end of summer. Thus, these results contribute to a better understanding of atmospheric (bio-)aerosol-cloud-interactions processes in the vulnerable Arctic environment but are also valuable for further developments of Earth system models that include ice nucleating and/or bioaerosol particles.
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| 7. |
- Pereira Freitas, Gabriel, 1993-, et al.
(författare)
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Emission of primary bioaerosol particles from Baltic seawater
- 2022
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Ingår i: Environmental Science. - : Royal Society of Chemistry (RSC). - 2634-3606. ; 2:5, s. 1170-1182
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Tidskriftsartikel (refereegranskat)abstract
- Bioaerosols are particles of biological origin with various important atmospheric implications, for example, within cloud formation where bioaerosols can act as cloud condensation or ice nuclei. Their sources and properties, however, are poorly understood. We conducted a controlled sea spray experiment to determine the properties and emission of primary biological aerosol particles (PBAP) originating from Baltic seawater. Using a single-particle fluorescence and light-scattering instrument, the Multiparameter Bioaerosol Spectrometer (MBS), we differentiated PBAP within sea spray aerosol (SSA). Overall, approximately 1 in 104 particles larger than 0.8 μm in diameter were classified as PBAP. The optically-determined morphology of the nascent and fluorescent SSA particles showed a clear transition in symmetry and elongation most likely due to changes in the biogeochemical properties of the surface water. These shifts were also reflected in a clear change of the bacterial community composition of the aerosol and seawater as determined by 16S rRNA-gene analysis, which were significantly distinct from each other, suggesting a preferential emission of specific bacteria to the atmosphere. Our results demonstrate the capability of the MBS to identify and count PBAP within SSA on a single-particle basis and will help to better constrain the emission of marine PBAP and their dependence on the seawater's biogeochemical properties.
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