Arctic fog chemistry induces the unexpected growth of Aitken mode particles to CCN-active particles

2021 ◽  
Author(s):  
Erik H. Hoffmann ◽  
Andreas Tilgner ◽  
Simonas Kecorius ◽  
Hartmut Herrmann
Keyword(s):  
Growth Mechanism ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Methanesulfonic Acid ◽  
Particle Growth ◽  
High Water ◽  
The Arctic ◽  
Radiative Balance ◽  
Active Particles ◽  
Aitken Mode

<p>New particle formation (NPF) and early growth are efficient processes producing high concentrations of cloud condensation nuclei (CCNs) precursors in the Arctic marine boundary layer (AMBL). However, due to short lifetime and lack of condensable vapors, newly formed particles do often not grow beyond 50 nm and cause low CCN particle concentrations in the AMBL. Thus, even the smallest amount of Aitken mode particle growth is capable to significantly increase the CCN budget. However, the growth mechanism of Aitken-mode particles from NPF into CCN range in the Arctic is still rather unclear and was therefore investigated during the cruise campaign PASCAL in 2017.</p> <p>During PASCAL, aerosol particles measurements were performed and an unexpected rapid growth of Aitken mode particles was observed right after fog episodes. Combined field data analyses and detailed multiphase chemistry box model simulations with the CAPRAM mechanism were performed to study the underlying processes. Resulting, a new mechanism is proposed explaining how particles with d < 50 nm are able to grow into CCN size range in the Arctic without requiring high water vapor supersaturation (SS). The investigations demonstrated that the rapid post-fog particle growth of Aitken mode is related to chemical processes within the Arctic fog. The redistribution of semi-volatile acidic (e.g., methanesulfonic acid) and basic (e.g., ammonia) compounds from processed CCN-active particles to smaller CCN-inactive particles can cause a rapid particle growth of Aitken mode particles after fog evaporation enabling them to grow towards CCN size. Comparisons of the model results with Berner impactor measurements supports the proposed growth mechanism.</p> <p>Overall, this study provided new insights on how the increasing frequency of NPF and fog-related particle processing can increase in the number of CCNs and cloud droplets leading to an increased albedo of Arctic clouds and thus affect the radiative balance in the Arctic. Since fogs will occur more frequently in the Arctic as a result of climate change, this growth mechanism and a deeper knowledge on its feedbacks can be essential to understand Arctic warming.</p>

scholarly journals Characterization of aerosol growth events over Ellesmere Island during the summers of 2015 and 2016

2019 ◽  
Vol 19 (8) ◽  
pp. 5589-5604 ◽  
Author(s):  
Samantha Tremblay ◽  
Jean-Christophe Picard ◽  
Jill O. Bachelder ◽  
Erik Lutsch ◽  
Kimberly Strong ◽  
...  
Keyword(s):  
Dimethyl Sulfide ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Methanesulfonic Acid ◽  
Particle Growth ◽  
Temperature Inversion ◽  
Ellesmere Island ◽  
The Arctic ◽  
Aerosol Composition ◽  
Aerosol Mass

Abstract. The occurrence of frequent aerosol nucleation and growth events in the Arctic during summertime may impact the region's climate through increasing the number of cloud condensation nuclei in the Arctic atmosphere. Measurements of aerosol size distributions and aerosol composition were taken during the summers of 2015 and 2016 at Eureka and Alert on Ellesmere Island in Nunavut, Canada. These results provide a better understanding of the frequency and spatial extent of elevated Aitken mode aerosol concentrations as well as of the composition and sources of aerosol mass during particle growth. Frequent appearances of small particles followed by growth occurred throughout the summer. These particle growth events were observed beginning in June with the melting of the sea ice rather than with the polar sunrise, which strongly suggests that influence from the marine boundary layer was the primary cause of the events. Correlated particle growth events at the two sites, separated by 480 km, indicate conditions existing over large scales play a key role in determining the timing and the characteristics of the events. In addition, aerosol mass spectrometry measurements were used to analyze the size-resolved chemical composition of aerosols during two selected growth events. It was found that particles with diameters between 50 and 80 nm (physical diameter) during these growth events were predominately organic with only a small sulfate contribution. The oxidation of the organics also changed with particle size, with the fraction of organic acids increasing with diameter from 80 to 400 nm. The growth events at Eureka were observed most often when the temperature inversion between the sea and the measurement site (at 610 m a.s.l.) was non-existent or weak, presumably creating conditions with low aerosol condensation sink and allowing fresh marine emissions to be mixed upward to the observatory's altitude. While the nature of the gaseous precursors responsible for the growth events is still poorly understood, oxidation of dimethyl sulfide alone to produce particle-phase sulfate or methanesulfonic acid was inconsistent with the measured aerosol composition, suggesting the importance of other gas-phase organic compounds condensing for particle growth.

scholarly journals Growth of nucleation mode particles in the summertime Arctic: a case study

2016 ◽  
Vol 16 (12) ◽  
pp. 7663-7679 ◽  
Author(s):  
Megan D. Willis ◽  
Julia Burkart ◽  
Jennie L. Thomas ◽  
Franziska Köllner ◽  
Johannes Schneider ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Methanesulfonic Acid ◽  
Lower Troposphere ◽  
Atmospheric Conditions ◽  
Aerosol Formation ◽  
Radiative Balance ◽  
Nucleation Mode ◽  
Cloud Properties ◽  
Marine Influence

Abstract. The summertime Arctic lower troposphere is a relatively pristine background aerosol environment dominated by nucleation and Aitken mode particles. Understanding the mechanisms that control the formation and growth of aerosol is crucial for our ability to predict cloud properties and therefore radiative balance and climate. We present an analysis of an aerosol growth event observed in the Canadian Arctic Archipelago during summer as part of the NETCARE project. Under stable and clean atmospheric conditions, with low inversion heights, carbon monoxide less than 80 ppbv, and black carbon less than 5 ng m−3, we observe growth of small particles,  <  20 nm in diameter, into sizes above 50 nm. Aerosol growth was correlated with the presence of organic species, trimethylamine, and methanesulfonic acid (MSA) in particles ∼ 80 nm and larger, where the organics are similar to those previously observed in marine settings. MSA-to-sulfate ratios as high as 0.15 were observed during aerosol growth, suggesting an important marine influence. The organic-rich aerosol contributes significantly to particles active as cloud condensation nuclei (CCN, supersaturation  =  0.6 %), which are elevated in concentration during aerosol growth above background levels of ∼ 100 to ∼ 220 cm−3. Results from this case study highlight the potential importance of secondary organic aerosol formation and its role in growing nucleation mode aerosol into CCN-active sizes in this remote marine environment.

scholarly journals Frequent Ultrafine Particle Formation and Growth in the Canadian Arctic Marine Environment

2017 ◽  
Author(s):  
Douglas B. Collins ◽  
Julia Burkart ◽  
Rachel Y.-W. Chang ◽  
Martine Lizotte ◽  
Aude Boivin-Rioux ◽  
...  
Keyword(s):  
Marine Environment ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Ultrafine Particle ◽  
Canadian Arctic ◽  
Cloud Droplet ◽  
The Arctic ◽  
Arctic Regions ◽  
Lower Cloud ◽  
Marine Microbial Communities

Abstract. The source strength and capability of aerosol particles in the Arctic to act as cloud condensation nuclei have important implications for understanding the indirect aerosol-cloud effect within the polar climate system. It has been shown in several Arctic regions that ultrafine particle (UFP) formation and growth is a key contributor to aerosol number concentrations during the summer. This study uses aerosol number size distribution measurements from ship-board measurement expeditions aboard the research icebreaker CCGS Amundsen in the summers of 2014 and 2016 throughout the Canadian Arctic to gain a deeper understanding of the drivers of UFP formation and growth within this marine boundary layer. UFP number concentrations (diameter > 4 nm) in the range of 101–104 cm−3 were observed across the two seasons, with concentrations greater than 103 cm−3 occurring more frequently in 2016. Higher concentrations in 2016 were associated with UFP formation and growth, with events occurring on 41 % of days, while events were only observed on 6 % of days in 2014. Assessment of relevant parameters for aerosol nucleation showed that the median condensation sink in this region was approximately 1.2 h−1 in 2016 and 2.2 h−1 in 2014, which lie at the lower end of ranges observed at even the most remote stations reported in the literature. Apparent growth rates of all observed events in both expeditions averaged 4.3 ± 4.1 nm h−1, in general agreement with other recent studies at similar latitudes. Higher solar radiation, lower cloud fractions, and lower sea ice concentrations combined with differences in the developmental stage and activity of marine microbial communities within the Canadian Arctic were documented and help explain differences between the aerosol measurements made during the 2014 and 2016 expeditions. These findings help to motivate further studies of biosphere-atmosphere interactions within the Arctic marine environment to explain the production of UFP and their growth to sizes relevant for cloud droplet activation.

scholarly journals Frequent ultrafine particle formation and growth in Canadian Arctic marine and coastal environments

2017 ◽  
Vol 17 (21) ◽  
pp. 13119-13138 ◽  
Author(s):  
Douglas B. Collins ◽  
Julia Burkart ◽  
Rachel Y.-W. Chang ◽  
Martine Lizotte ◽  
Aude Boivin-Rioux ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Ultrafine Particle ◽  
Canadian Arctic ◽  
Cloud Droplet ◽  
The Arctic ◽  
Polar Climate ◽  
Arctic Regions ◽  
Lower Cloud ◽  
Marine Microbial Communities

Abstract. The source strength and capability of aerosol particles in the Arctic to act as cloud condensation nuclei have important implications for understanding the indirect aerosol–cloud effect within the polar climate system. It has been shown in several Arctic regions that ultrafine particle (UFP) formation and growth is a key contributor to aerosol number concentrations during the summer. This study uses aerosol number size distribution measurements from shipboard expeditions aboard the research icebreaker CCGS Amundsen in the summers of 2014 and 2016 throughout the Canadian Arctic to gain a deeper understanding of the drivers of UFP formation and growth within this marine boundary layer. UFP number concentrations (diameter > 4 nm) in the range of 101–104 cm−3 were observed during the two seasons, with concentrations greater than 103 cm−3 occurring more frequently in 2016. Higher concentrations in 2016 were associated with UFP formation and growth, with events occurring on 41 % of days, while events were only observed on 6 % of days in 2014. Assessment of relevant parameters for aerosol nucleation showed that the median condensation sink in this region was approximately 1.2 h−1 in 2016 and 2.2 h−1 in 2014, which lie at the lower end of ranges observed at even the most remote stations reported in the literature. Apparent growth rates of all observed events in both expeditions averaged 4.3 ± 4.1 nm h−1, in general agreement with other recent studies at similar latitudes. Higher solar radiation, lower cloud fractions, and lower sea ice concentrations combined with differences in the developmental stage and activity of marine microbial communities within the Canadian Arctic were documented and help explain differences between the aerosol measurements made during the 2014 and 2016 expeditions. These findings help to motivate further studies of biosphere–atmosphere interactions within the Arctic marine environment to explain the production of UFP and their growth to sizes relevant for cloud droplet activation.

scholarly journals Characterization of aerosol growth events over Ellesmere Island during the summers of 2015 and 2016

2018 ◽  
Author(s):  
Samantha Tremblay ◽  
Jean-Christophe Picard ◽  
Jill O. Bachelder ◽  
Erik Lutsch ◽  
Kimberly Strong ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Particle Growth ◽  
Temperature Inversion ◽  
Nucleation And Growth ◽  
Ellesmere Island ◽  
The Arctic ◽  
Particle Nucleation ◽  
Particle Phase ◽  
Aerosol Composition ◽  
Aerosol Mass

Abstract. The occurrence of frequent aerosol nucleation and growth events in the Arctic during summertime may impact the region’s climate through increasing the number of cloud condensation nuclei in the Arctic atmosphere. Measurements of aerosol size distributions and aerosol composition were taken during the summers of 2015 and 2016 at Eureka and Alert on Ellesmere Island in Nunavut, Canada. The corresponding results provide a better understanding of the frequency and spatial extent of these nucleation and growth events as well as of the composition and sources of aerosol mass during particle growth. These events are observed beginning in June with the melting of the sea ice rather than with polar sunrise, which strongly suggests emissions from marine sources are the primary cause of the events. Frequent particle nucleation followed by growth occurs throughout the summer. Correlated particle growths events at the two sites, separated by 480 km, indicate conditions existing over such large scales play a key role in determining the timing and the characteristics of the events. In addition, aerosol mass spectrometry measurements are used to analyze the size-resolved chemical composition of aerosols during two selected growth events. It is found that particles with diameters smaller than 100 nm are predominately organic with only a small sulphate contribution. The oxidation of the organic fraction also changes with particle size with larger particles containing a greater fraction of organic acids relative to other non-acid oxygenates (e.g. alcohols or aldehydes). It is also observed that the relative amount of m / z 44 in the measured mass spectra increases during the growth events suggesting increases in organic acid concentrations in the particle phase. The nucleation and growth events at Eureka are observed most often when the temperature inversion between the sea and the measurement site (at 610 m a.s.l.) is non-existent or weak allowing presumably fresh marine emissions to be mixed upward to the observatory altitude. While the nature of the gaseous precursors responsible for the growth events are poorly understood, oxidation of dimethyl sulphide alone to produce particle phase sulphate or methanesulphonic acid is not consistent with the measured aerosol composition, suggesting the importance of condensation of other gas phase organic compounds for particle growth.

scholarly journals Large contribution of organics to condensational growth and formation of cloud condensation nuclei (CCN) in remote marine boundary layer

2020 ◽  
Author(s):  
Guangjie Zheng ◽  
Chongai Kuang ◽  
Janek Uin ◽  
Thomas Watson ◽  
Jian Wang
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Global Climate ◽  
Biological Activities ◽  
Cloud Condensation Nuclei ◽  
Particle Growth ◽  
Large Contribution ◽  
Condensation Nuclei ◽  
Condensational Growth

Abstract. Marine low clouds strongly influence global climate, and their radiative effects are particularly susceptible to the concentration of cloud condensation nuclei (CCN). One major source of CCN is condensational growth of pre-CCN particles, and sulfate has long been considered the major condensing species in remote marine boundary layer. While some studies suggested that secondary organic species can contribute to the particle growth, its importance remains unclear. Here we present the first long-term observational evidence that organics play an important role in particle growth over remote oceans. To the contrary of traditional thinking, sulfate dominated condensational growth for only a small (∼18 %) fraction of the 62 observed growth events, even fewer than the organic-dominated events (24 %). During most (58 %) growth events, the major condensing species included both organics and sulfate. Potential precursors of the secondary organics are volatile organic compounds from ocean biological activities and those produced by the air-sea interfacial oxidation. Our results indicate that the condensation of secondary organics contributes strongly to the growth of pre-CCN particles, and thereby the CCN population over remote oceans.

scholarly journals Cloud condensation nuclei over the Southern Ocean: wind dependence and seasonal cycles

2017 ◽  
Vol 17 (7) ◽  
pp. 4419-4432 ◽  
Author(s):  
John L. Gras ◽  
Melita Keywood
Keyword(s):  
Wind Speed ◽  
Southern Ocean ◽  
Marine Boundary Layer ◽  
Numerical Models ◽  
Cloud Condensation Nuclei ◽  
Sea Salt ◽  
Aerosol Size Distribution ◽  
Condensation Nuclei ◽  
Coarse Mode ◽  
Aitken Mode

Abstract. Multi-decadal observations of aerosol microphysical properties from regionally representative sites can be used to challenge regional or global numerical models that simulate atmospheric aerosol. Presented here is an analysis of multi-decadal observations at Cape Grim (Australia) that characterise production and removal of the background marine aerosol in the Southern Ocean marine boundary layer (MBL) on both short-term weather-related and underlying seasonal scales.A trimodal aerosol distribution comprises Aitken nuclei (< 100 nm), cloud condensation nuclei (CCN)/accumulation (100–350 nm) and coarse-particle (> 350 nm) modes, with the Aitken mode dominating number concentration. Whilst the integrated particle number in the MBL over the clean Southern Ocean is only weakly dependent on wind speed, the different modes in the aerosol size distribution vary in their relationship with wind speed. The balance between a positive wind dependence in the coarse mode and negative dependence in the accumulation/CCN mode leads to a relatively flat wind dependence in summer and moderately strong positive wind dependence in winter. The changeover in wind dependence of these two modes occurs in a very small size range at the mode intersection, indicative of differences in the balance of production and removal in the coarse and accumulation/CCN modes.Whilst a marine biological source of reduced sulfur appears to dominate CCN concentration over the summer months (December to February), other components contribute to CCN over the full annual cycle. Wind-generated coarse-mode sea salt is an important CCN component year round and is the second-most-important contributor to CCN from autumn through to mid-spring (March to November). A portion of the non-seasonally dependent contributor to CCN can clearly be attributed to wind-generated sea salt, with the remaining part potentially being attributed to long-range-transported material. Under conditions of greater supersaturation, as expected in more convective cyclonic systems and their associated fronts, Aitken mode particles become increasingly important as CCN.

scholarly journals Ion-induced sulfuric acid–ammonia nucleation drives particle formation in coastal Antarctica

2018 ◽  
Vol 4 (11) ◽  
pp. eaat9744 ◽  
Author(s):  
T. Jokinen ◽  
M. Sipilä ◽  
J. Kontkanen ◽  
V. Vakkari ◽  
P. Tisler ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Particle Growth ◽  
Field Studies ◽  
Particle Formation ◽  
New Particle Formation ◽  
Aerosol Formation ◽  
Radiative Balance ◽  
Secondary Aerosol

Formation of new aerosol particles from trace gases is a major source of cloud condensation nuclei (CCN) in the global atmosphere, with potentially large effects on cloud optical properties and Earth’s radiative balance. Controlled laboratory experiments have resolved, in detail, the different nucleation pathways likely responsible for atmospheric new particle formation, yet very little is known from field studies about the molecular steps and compounds involved in different regions of the atmosphere. The scarcity of primary particle sources makes secondary aerosol formation particularly important in the Antarctic atmosphere. Here, we report on the observation of ion-induced nucleation of sulfuric acid and ammonia—a process experimentally investigated by the CERN CLOUD experiment—as a major source of secondary aerosol particles over coastal Antarctica. We further show that measured high sulfuric acid concentrations, exceeding 107 molecules cm−3, are sufficient to explain the observed new particle growth rates. Our findings show that ion-induced nucleation is the dominant particle formation mechanism, implying that galactic cosmic radiation plays a key role in new particle formation in the pristine Antarctic atmosphere.

scholarly journals Aitken mode particles as CCN in aerosol- and updraft-sensitive regimes of cloud droplet formation

2021 ◽  
Author(s):  
Mira L. Pöhlker ◽  
Minghui Zhang ◽  
Ramon Campos Braga ◽  
Ovid O. Krüger ◽  
Ulrich Pöschl ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Threshold Level ◽  
Droplet Formation ◽  
Global Scale ◽  
Number Concentration ◽  
The Arctic ◽  
Accumulation Mode ◽  
Aerosol Cloud ◽  
Aitken Mode

Abstract. The high variability of aerosol particle concentrations, sizes and chemical composition makes their description challenging in atmospheric models. Aerosol-cloud interaction studies are usually focused on the activation of accumulation mode particles as cloud condensation nuclei (CCN). However, under specific conditions also Aitken mode particles can contribute to the number concentration of cloud droplets (Nd), leading to large uncertainties in predicted cloud properties on a global scale. We perform sensitivity studies with an adiabatic cloud parcel model to constrain conditions, under which Aitken mode particles contribute to Nd. The simulations cover wide ranges of aerosol properties, such as total particle number concentration, hygroscopicity (κ) and mode diameters for accumulation and Aitken mode particles. Building upon the previously suggested concept of updraft (w)- and aerosol-limited regimes of cloud droplet formation, we show that activation of Aitken mode particles does not occur in w-limited regimes of accumulation mode particles. The transitional range between the regimes is broadened when Aitken mode particles contribute to Nd as aerosol-limitation requires much higher w than for aerosol size distributions with accumulation mode particles only. In the transitional regime, Nd is similarly dependent on w and κ. Therefore, we analyze the sensitivity of Nd to κ, ξ(κ), as a function of w to identify the value combinations, above which Aitken mode particles can affect Nd. As ξ(κ) shows a minimum when the smallest activated particle size is in the range of the Hoppel minimum (0.06 μm ≤ Dmin ≤ 0.08 μm), the corresponding (w,κ) pairs can be considered a threshold level, above which Aitken mode particles have significant impact on Nd. This threshold is largely determined by the number concentration of accumulation mode particles and by the Aitken mode diameter. Our analysis of these thresholds results in a simple parametric framework and criterion to identify aerosol and updraft conditions, under which Aitken mode particles are expected to affect aerosol-cloud interactions. Our results confirm that Aitken mode particles likely do not contribute to Nd in polluted air masses (urban, biomass burning) at moderate updraft velocities (w ≤ 3 m s−1), but may be important in deep convective clouds. Under clean conditions, such as in the Amazon, the Arctic, and remote ocean regions, hygroscopic Aitken mode particles can act as CCN at updrafts of w 

scholarly journals Intercomparison and evaluation of aerosol microphysical properties among AeroCom global models of a range of complexity

2013 ◽  
Vol 13 (11) ◽  
pp. 30841-30928 ◽  
Author(s):  
G. W. Mann ◽  
K. S. Carslaw ◽  
C. L. Reddington ◽  
K. J. Pringle ◽  
M. Schulz ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Climate Models ◽  
Global Climate ◽  
Cloud Condensation Nuclei ◽  
Global Climate Models ◽  
The Arctic ◽  
Global Variation ◽  
Aitken Mode

Abstract. Many of the next generation of global climate models will include aerosol schemes which explicitly simulate the microphysical processes that determine the particle size distribution. These models enable aerosol optical properties and cloud condensation nuclei (CCN) concentrations to be determined by fundamental aerosol processes, which should lead to a more physically based simulation of aerosol direct and indirect radiative forcings. This study examines the global variation in particle size distribution simulated by twelve global aerosol microphysics models to quantify model diversity and to identify any common biases against observations. Evaluation against size distribution measurements from a new European network of aerosol supersites shows that the mean model agrees quite well with the observations at many sites on the annual mean, but there are some seasonal biases common to many sites. In particular, at many of these European sites, the accumulation mode number concentration is biased low during winter and Aitken mode concentrations tend to be overestimated in winter and underestimated in summer. At high northern latitudes, the models strongly underpredict Aitken and accumulation particle concentrations compared to the measurements, consistent with previous studies that have highlighted the poor performance of global aerosol models in the Arctic. In the marine boundary layer, the models capture the observed meridional variation in the size distribution, which is dominated by the Aitken mode at high latitudes, with an increasing concentration of accumulation particles with decreasing latitude. Considering vertical profiles, the models reproduce the observed peak in total particle concentrations in the upper troposphere due to new particle formation, although modelled peak concentrations tend to be biased high over Europe. Overall, the multi-model-mean dataset simulates the global variation of the particle size distribution with a good degree of skill, suggesting that most of the individual global aerosol microphysics models are performing well, although the large model diversity indicates that some models are in poor agreement with the observations. Further work is required to better constrain size-resolved primary and secondary particle number sources, and an improved understanding of nucleation and growth (e.g. the role of nitrate and secondary organics) will improve the fidelity of simulated particle size distributions.

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