scholarly journals Cloud condensation nuclei closure study on summer arctic aerosol

2011 ◽  
Vol 11 (3) ◽  
pp. 8801-8840
Author(s):  
M. Martin ◽  
R. Y.-W. Chang ◽  
B. Sierau ◽  
S. Sjogren ◽  
E. Swietlicki ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
High Arctic ◽  
Number Concentration ◽  
The Arctic ◽  
Mass Composition ◽  
Condensation Nuclei ◽  
Aerosol Mass ◽  
Arctic Aerosol ◽  
Kohler Theory ◽  
Ocean Study

Abstract. We present an aerosol – cloud condensation nuclei CCN) closure study on summer high Arctic aerosol based on measurements that were carried out in summer 2008 during the Arctic Summer Cloud Ocean Study (ASCOS) on board the Swedish ice breaker Oden. The data presented here were collected during a three-week time period in the pack ice (>85° N) when the icebreaker Oden was moored to an ice floe and drifted passively during the most biological active period into autumn freeze up conditions. CCN number concentrations were obtained using two CCN counters measuring at different supersaturations. The directly measured CCN number concentration is then compared with a CCN number concentration calculated using both bulk aerosol mass composition data from an aerosol mass spectrometer and aerosol number size distributions obtained from a differential mobility particle sizer, assuming κ-Köhler theory and an internally mixed aerosol. For the two highest measured supersaturations, 0.73 and 0.41%, closure could not be achieved with the investigated settings concerning hygroscopicity and density. The calculated CCN number concentration was always higher than the measured one. One possible explanation is that the smaller particles that activate at these supersaturations have a relative larger insoluble organic mass fraction and thus are less good CCN than the larger particles. At 0.20, 0.15 and 0.10% supersaturation, the measured CCN number can be represented with different parameters for the hygroscopicity and density of the particles. For the best agreement of the calculated CCNnumber concentration with the measured one the organic fraction of the aerosol needs to be nearly insoluble (қorg=0.02). However, this is not unambigious and қorg=0.2 is found as an upper limit at 0.1% supersaturation.

scholarly journals Cloud condensation nuclei closure study on summer arctic aerosol

2011 ◽  
Vol 11 (22) ◽  
pp. 11335-11350 ◽  
Author(s):  
M. Martin ◽  
R. Y.-W. Chang ◽  
B. Sierau ◽  
S. Sjogren ◽  
E. Swietlicki ◽  
...  
Keyword(s):  
Mass Fraction ◽  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
The Arctic ◽  
Mass Composition ◽  
Organic Mass ◽  
Condensation Nuclei ◽  
Differential Mobility ◽  
Aerosol Mass ◽  
Arctic Aerosol

Abstract. We present an aerosol – cloud condensation nuclei (CCN) closure study on summer high Arctic aerosol based on measurements that were carried out in 2008 during the Arctic Summer Cloud Ocean Study (ASCOS) on board the Swedish ice breaker Oden. The data presented here were collected during a three-week time period in the pack ice (>85° N) when the icebreaker Oden was moored to an ice floe and drifted passively during the most biological active period into autumn freeze up conditions. CCN number concentrations were obtained using two CCN counters measuring at different supersaturations. The directly measured CCN number concentration was then compared with a CCN number concentration calculated using both bulk aerosol mass composition data from an aerosol mass spectrometer (AMS) and aerosol number size distributions obtained from a differential mobility particle sizer, assuming κ-Köhler theory, surface tension of water and an internally mixed aerosol. The last assumption was supported by measurements made with a hygroscopic tandem differential mobility analyzer (HTDMA) for particles >70 nm. For the two highest measured supersaturations, 0.73 and 0.41%, closure could not be achieved with the investigated settings concerning hygroscopicity and density. The calculated CCN number concentration was always higher than the measured one for those two supersaturations. This might be caused by a relative larger insoluble organic mass fraction of the smaller particles that activate at these supersaturations, which are thus less good CCN than the larger particles. On average, 36% of the mass measured with the AMS was organic mass. At 0.20, 0.15 and 0.10% supersaturation, closure could be achieved with different combinations of hygroscopic parameters and densities within the uncertainty range of the fit. The best agreement of the calculated CCN number concentration with the observed one was achieved when the organic fraction of the aerosol was treated as nearly water insoluble (κorg=0.02), leading to a mean total κ, κtot, of 0.33 ± 0.13. However, several settings led to closure and κorg=0.2 is found to be an upper limit at 0.1% supersaturation. κorg≤0.2 leads to a κtot range of 0.33 ± 013 to 0.50 ± 0.11. Thus, the organic material ranges from being sparingly soluble to effectively insoluble. These results suggest that an increase in organic mass fraction in particles of a certain size would lead to a suppression of the Arctic CCN activity.

scholarly journals Simultaneous measurements of aerosol size distributions at three sites in the European high Arctic

2019 ◽  
Vol 19 (11) ◽  
pp. 7377-7395 ◽  
Author(s):  
Manuel Dall'Osto ◽  
David C. S. Beddows ◽  
Peter Tunved ◽  
Roy M. Harrison ◽  
Angelo Lupi ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Cloud Condensation Nuclei ◽  
High Arctic ◽  
The Arctic ◽  
Research Station ◽  
Size Distributions ◽  
Aerosol Formation ◽  
Condensation Nuclei ◽  
Main Mode ◽  
Accumulation Mode

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-range-transported – 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 (2013–2015). 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 north-eastern Greenland. The GRU site is included in an inter-site comparison for the first time. K-means cluster analysis provided 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.

scholarly journals Closure between measured and modeled cloud condensation nuclei (CCN) using size-resolved aerosol compositions in downtown Toronto

2005 ◽  
Vol 5 (4) ◽  
pp. 6263-6293 ◽  
Author(s):  
K. Broekhuizen ◽  
R. Y.-W. Chang ◽  
W. R. Leaitch ◽  
S.-M. Li ◽  
J. P. D. Abbatt
Keyword(s):  
Cloud Condensation Nuclei ◽  
Compositional Analysis ◽  
Diffusion Chamber ◽  
Aerosol Size Distribution ◽  
Condensation Nuclei ◽  
Aerosol Composition ◽  
Average Value ◽  
Aerosol Mass ◽  
Gradient Diffusion ◽  
Kohler Theory

Abstract. Measurements of cloud condensation nuclei (CCN) were made in downtown Toronto during August and September, 2003. CCN measurements were performed at 0.58% supersaturation using a thermal-gradient diffusion chamber, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and APS system and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. Aerosol composition data shows that the particles were predominately organic in nature, in particular for those with a vacuum aerodynamic diameter of <25 μm. In this study, the largest contribution to CCN concentrations came from this size range, suggesting that the CCN are also organic-rich. Using the size and composition information, a detailed CCN closure analysis was performed. In all analyses, the particles were assumed to be internally mixed, the organic fraction was assumed to be insoluble, and the inorganic fraction was assumed to be ammonium sulfate. The AMS time-of-flight data were used for Köhler theory predictions for each particle size and composition to obtain the dry diameter required for activation. By so doing, this closure analysis yielded an average value of CCNpredicted/CCNobserved= 1.04 (R2=0.87). Several other closure analyses were performed to mimic other methods of aerosol compositional analysis. In all cases, by assuming uniform aerosol composition across a wider range of particle sizes, significant overprediction of CCN concentrations resulted.

scholarly journals Apportioning aerosol natural and anthropogenic sources thorough simultaneous aerosol size distributions and chemical composition in the European high Arctic

2018 ◽  
Author(s):  
Manuel Dall'Osto ◽  
David C. S. Beddows ◽  
Peter Tunved ◽  
Roy M. Harrison ◽  
Angelo Lupi ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Cloud Condensation Nuclei ◽  
High Arctic ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Research Station ◽  
Size Distributions ◽  
Condensation Nuclei ◽  
Main Mode ◽  
Accumulation Mode

Abstract. Understanding aerosol size distributions is crucial to our ability to predict aerosol number concentrations. When of favourable size and composition, both long range transported particles as well as locally formed ones may serve as Cloud Condensation Nuclei (CCN); small changes may have a large impact on the low CCN concentrations currently characteristic of the Arctic environment. Here, we present a cluster analysis of particle size distributions (PSD, size range 8–500 nm) simultaneously collected from three high Arctic sites across Europe during a three year period (2013–2015). Two sites are located in the Svalbard archipelago: Zeppelin research station (474 m above ground), and the nearby Gruvebadet Observatory (about 2 km distance from Zepplelin, 67 m above ground). The third site (Villum Research Station – Station Nord, 30 m above ground) is 600 km to the west-northwest of Zeppelin, at the tip of north-eastern Greenland. An inter-site comparison exercise is carried out for the first time including the Gruvebadet site. K-means analysis provided eight specific aerosol categories, further combined into broad PSD with similar characteristics, namely: pristine low concentrations (12–14 %), 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 shows PSD 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, associated with sea spray (largest detectable sizes), Arctic haze (main mode at 150 nm) and aged accumulation mode (main mode at 220 nm) aerosols. In contrast, locally produced and most likely of marine biogenic origin particles exhibit size distributions dominated by the nucleation and Atiken mode aerosol during summer months. The obtained data and analysis set now the stage for future studies; including apportioning the relative contribution of primary and secondary aerosol formation processes to the aerosol size distribution in high Arctic, and elucidating anthropogenic aerosol dynamics, transport and removal processes across the Greenland sea. In a region of enormous importance for future climate on Earth, it is imperative to continue strengthening international scientific cooperation, in order to address important research questions on scales beyond singular station or measurement events.

scholarly journals Closure between measured and modeled cloud condensation nuclei (CCN) using size-resolved aerosol compositions in downtown Toronto

2006 ◽  
Vol 6 (9) ◽  
pp. 2513-2524 ◽  
Author(s):  
K. Broekhuizen ◽  
R.Y.-W. Chang ◽  
W. R. Leaitch ◽  
S.-M. Li ◽  
J. P. D. Abbatt
Keyword(s):  
Cloud Condensation Nuclei ◽  
Diffusion Chamber ◽  
Droplet Surface ◽  
Aerosol Size Distribution ◽  
Condensation Nuclei ◽  
Aerosol Composition ◽  
Average Value ◽  
Aerosol Mass ◽  
Gradient Diffusion ◽  
Kohler Theory

Abstract. Measurements of cloud condensation nuclei (CCN) were made in downtown Toronto during August and September, 2003. CCN measurements were performed at 0.58% supersaturation using a thermal-gradient diffusion chamber, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and APS system and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. Aerosol composition data shows that the particles were predominately organic in nature, in particular for those with a vacuum aerodynamic diameter of <0.25 µm. In this study, the largest contribution to CCN concentrations came from this size range, suggesting that the CCN are also organic-rich. Using the size and composition information, detailed CCN closure analyses were performed. In the first analysis, the particles were assumed to be internally mixed, the organic fraction was assumed to be insoluble, and the inorganic fraction was assumed to be ammonium sulfate. The AMS time-of-flight data were used for Köhler theory predictions for each particle size and composition to obtain the dry diameter required for activation. By so doing, this closure analysis yielded an average value of CCNpredicted/CCNobserved=1.12±0.05. However, several sample days showed distinct bimodal distributions, and a closure analysis was performed after decoupling the two particle modes. This analysis yielded an average value of CCNpredicted/CCNobserved=1.03±0.05. A sensitivity analysis was also performed to determine the aerosol/CCN closure if the organic solubility, droplet surface tension, or chamber supersaturation were varied.

scholarly journals Aircraft-based measurements of High Arctic springtime aerosol show evidence for vertically varying sources, transport and composition

2019 ◽  
Vol 19 (1) ◽  
pp. 57-76 ◽  
Author(s):  
Megan D. Willis ◽  
Heiko Bozem ◽  
Daniel Kunkel ◽  
Alex K. Y. Lee ◽  
Hannes Schulz ◽  
...  
Keyword(s):  
Potential Temperature ◽  
High Arctic ◽  
The Arctic ◽  
Chemical Transformations ◽  
Aerosol Composition ◽  
Air Masses ◽  
Aerosol Mass ◽  
Arctic Aerosol ◽  
Show Evidence ◽  
Climate Interactions

Abstract. The sources, chemical transformations and removal mechanisms of aerosol transported to the Arctic are key factors that control Arctic aerosol–climate interactions. Our understanding of sources and processes is limited by a lack of vertically resolved observations in remote Arctic regions. We present vertically resolved observations of trace gases and aerosol composition in High Arctic springtime, made largely north of 80∘ N, during the NETCARE campaign. Trace gas gradients observed on these flights defined the polar dome as north of 66–68∘ 30′ N and below potential temperatures of 283.5–287.5 K. In the polar dome, we observe evidence for vertically varying source regions and chemical processing. These vertical changes in sources and chemistry lead to systematic variation in aerosol composition as a function of potential temperature. We show evidence for sources of aerosol with higher organic aerosol (OA), ammonium and refractory black carbon (rBC) content in the upper polar dome. Based on FLEXPART-ECMWF calculations, air masses sampled at all levels inside the polar dome (i.e., potential temperature <280.5 K, altitude <∼3.5 km) subsided during transport over transport times of at least 10 days. Air masses at the lowest potential temperatures, in the lower polar dome, had spent long periods (>10 days) in the Arctic, while air masses in the upper polar dome had entered the Arctic more recently. Variations in aerosol composition were closely related to transport history. In the lower polar dome, the measured sub-micron aerosol mass was dominated by sulfate (mean 74 %), with lower contributions from rBC (1 %), ammonium (4 %) and OA (20 %). At higher altitudes and higher potential temperatures, OA, ammonium and rBC contributed 42 %, 8 % and 2 % of aerosol mass, respectively. A qualitative indication for the presence of sea salt showed that sodium chloride contributed to sub-micron aerosol in the lower polar dome, but was not detectable in the upper polar dome. Our observations highlight the differences in Arctic aerosol chemistry observed at surface-based sites and the aerosol transported throughout the depth of the Arctic troposphere in spring.

scholarly journals Method to retrieve cloud condensation nuclei number concentrations using lidar measurements

2019 ◽  
Vol 12 (7) ◽  
pp. 3825-3839 ◽  
Author(s):  
Wangshu Tan ◽  
Gang Zhao ◽  
Yingli Yu ◽  
Chengcai Li ◽  
Jian Li ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
New Method ◽  
Cloud Base ◽  
Chemical Compositions ◽  
Condensation Nuclei ◽  
Aerosol Cloud ◽  
Lidar Measurements ◽  
Kohler Theory ◽  
Aerosol Cloud Interactions

Abstract. Determination of cloud condensation nuclei (CCN) number concentrations at cloud base is important to constrain aerosol–cloud interactions. A new method to retrieve CCN number concentrations using backscatter and extinction profiles from multiwavelength Raman lidars is proposed. The method implements hygroscopic enhancements of backscatter and extinction with relative humidity to derive dry backscatter and extinction and humidogram parameters. Humidogram parameters, Ångström exponents, and lidar extinction-to-backscatter ratios are then linked to the ratio of CCN number concentration to dry backscatter and extinction coefficient (ARξ). This linkage is established based on the datasets simulated by Mie theory and κ-Köhler theory with in-situ-measured particle size distributions and chemical compositions. CCN number concentration can thus be calculated with ARξ and dry backscatter and extinction. An independent theoretical simulated dataset is used to validate this new method and results show that the retrieved CCN number concentrations at supersaturations of 0.07 %, 0.10 %, and 0.20 % are in good agreement with theoretical calculated values. Sensitivity tests indicate that retrieval error in CCN arises mostly from uncertainties in extinction coefficients and RH profiles. The proposed method improves CCN retrieval from lidar measurements and has great potential in deriving scarce long-term CCN data at cloud base, which benefits aerosol–cloud interaction studies.

scholarly journals New particle formation and its effect on cloud condensation nuclei abundance in the summer Arctic: a case study in the Fram Strait and Barents Sea

2019 ◽  
Vol 19 (22) ◽  
pp. 14339-14364 ◽  
Author(s):  
Simonas Kecorius ◽  
Teresa Vogl ◽  
Pauli Paasonen ◽  
Janne Lampilahti ◽  
Daniel Rothenberg ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Negative Ions ◽  
Particle Formation ◽  
Number Concentration ◽  
The Arctic ◽  
New Particle Formation ◽  
Condensation Nuclei ◽  
Nucleation Mode ◽  
Particle Formation And Growth

Abstract. In a warming Arctic the increased occurrence of new particle formation (NPF) is believed to originate from the declining ice coverage during summertime. Understanding the physico-chemical properties of newly formed particles, as well as mechanisms that control both particle formation and growth in this pristine environment, is important for interpreting aerosol–cloud interactions, to which the Arctic climate can be highly sensitive. In this investigation, we present the analysis of NPF and growth in the high summer Arctic. The measurements were made on-board research vessel Polarstern during the PS106 Arctic expedition. Four distinctive NPF and subsequent particle growth events were observed, during which particle (diameter in a range 10–50 nm) number concentrations increased from background values of approx. 40 up to 4000 cm−3. Based on particle formation and growth rates, as well as hygroscopicity of nucleation and the Aitken mode particles, we distinguished two different types of NPF events. First, some NPF events were favored by negative ions, resulting in more-hygroscopic nucleation mode particles and suggesting sulfuric acid as a precursor gas. Second, other NPF events resulted in less-hygroscopic particles, indicating the influence of organic vapors on particle formation and growth. To test the climatic relevance of NPF and its influence on the cloud condensation nuclei (CCN) budget in the Arctic, we applied a zero-dimensional, adiabatic cloud parcel model. At an updraft velocity of 0.1 m s−1, the particle number size distribution (PNSD) generated during nucleation processes resulted in an increase in the CCN number concentration by a factor of 2 to 5 compared to the background CCN concentrations. This result was confirmed by the directly measured CCN number concentrations. Although particles did not grow beyond 50 nm in diameter and the activated fraction of 15–50 nm particles was on average below 10 %, it could be shown that the sheer number of particles produced by the nucleation process is enough to significantly influence the background CCN number concentration. This implies that NPF can be an important source of CCN in the Arctic. However, more studies should be conducted in the future to understand mechanisms of NPF, sources of precursor gases and condensable vapors, as well as the role of the aged nucleation mode particles in Arctic cloud formation.

scholarly journals Method to retrieve cloud condensation nuclei number concentrations using lidar measurements

2019 ◽  
Author(s):  
Wangshu Tan ◽  
Gang Zhao ◽  
Yingli Yu ◽  
Chengcai Li ◽  
Jian Li ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
New Method ◽  
Cloud Base ◽  
Chemical Compositions ◽  
Condensation Nuclei ◽  
Aerosol Cloud ◽  
Lidar Measurements ◽  
Kohler Theory ◽  
Aerosol Cloud Interactions

Abstract. Determination of cloud condensation nuclei (CCN) number concentrations at cloud base is important to constrain aerosol-cloud interactions. A new method to retrieve CCN number concentrations using backscatter and extinction profiles from multiwavelength Raman lidars is proposed. The method implements hygroscopic enhancements of backscatter/extinction with relative humidity to derive dry backscatter/extinction and humidogram parameters. Humidogram parameters, Ångström exponents, and lidar extinction-to-backscatter ratios are then linked to the ratio of CCN number concentration to dry backscatter/extinction coefficient (ARξ). This linkage is established based on the datasets simulated by Mie theory and κ-Köhler theory with in situ measured particle size distributions and chemical compositions. CCN number concentration can thus be calculated with ARξ and dry backscatter/extinction. An independent theoretical simulated datasets is used to validate this new method and results show that the retrieved CCN number concentrations at supersaturations of 0.07 %, 0.10 %, and 0.20 % are in good agreement with theoretical calculated values. Sensitivity tests indicate that retrieval error in CCN arise mostly from uncertainties in extinction coefficients and RH profiles. The proposed method improves CCN retrieval from lidar measurements and has great potential in deriving scarce long-term CCN data at cloud base which benefits aerosol-cloud interaction studies.

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