scholarly journals Indoor Sources of Ultrafine and Accumulation Mode Particles: Size Distributions, Size-Resolved Concentrations, and Source Strengths

2006 ◽  
Vol 40 (5) ◽  
pp. 348-360 ◽  
Author(s):  
Lance Wallace
Keyword(s):  
Size Distributions ◽  
Accumulation Mode ◽  
Indoor Sources

scholarly journals Pan-Arctic aerosol number size distributions: seasonality and transport patterns

2017 ◽  
Vol 17 (13) ◽  
pp. 8101-8128 ◽  
Author(s):  
Eyal Freud ◽  
Radovan Krejci ◽  
Peter Tunved ◽  
Richard Leaitch ◽  
Quynh T. Nguyen ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Regional Scale ◽  
Arctic Region ◽  
The Arctic ◽  
Research Station ◽  
Size Distributions ◽  
Back Trajectories ◽  
Accumulation Mode ◽  
Source Regions ◽  
The Arctic Ocean

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  ∼ 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 (Nacc) 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 Nacc, 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 Nacc 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.

scholarly journals Improving the simulation of global aerosol with size-segregated anthropogenic number emissions

2017 ◽  
Author(s):  
Filippo Xausa ◽  
Pauli Paasonen ◽  
Risto Makkonen ◽  
Mikhail Arshinov ◽  
Aijun Ding ◽  
...  
Keyword(s):  
Particle Number ◽  
Climate Models ◽  
Climate Model ◽  
Dominant Role ◽  
Particle Diameter ◽  
Radiation Budget ◽  
Size Distributions ◽  
Anthropogenic Aerosol ◽  
Accumulation Mode ◽  
Climate Interactions

Abstract. Climate models are important tools that are used for generating climate change projections, in which aerosol-climate interactions are one of the main sources of uncertainties. In order to quantify aerosol-radiation and aerosol-cloud interactions, detailed input of anthropogenic aerosol number emissions is necessary. However, the anthropogenic aerosol number emissions are usually converted from the corresponding mass emissions in precompiled emission inventories through a very simplistic method depending uniquely on chemical composition, particle size and density, which are defined for a few very wide main source sectors. In this work, the anthropogenic particle number emissions converted from the AeroCom mass in the ECHAM-HAM climate model were replaced with the recently-formulated number emissions from the Greenhouse Gas and Air Pollution Interactions and Synergies (GAINS)-model, where the emission number size distributions vary, for example, with respect to the fuel and technology. A special attention in our analysis was put on accumulation mode particles (particle diameter dp > 100 nm) because of (i) their capability of acting as cloud condensation nuclei (CCN), thus forming cloud droplets and affecting Earth's radiation budget, and (ii) their dominant role in forming the coagulation sink and thus limiting the concentration of sub-100 nanometers particles. In addition, the estimates of anthropogenic CCN formation, and thus the forcing from aerosol-climate interactions are expected to be affected. Analysis of global particle number concentrations and size distributions reveal that GAINS implementation increases CCN concentration compared with AeroCom, with regional enhancement factors reaching values as high as 10. A comparison between modeled and observed concentrations shows that the increase in number concentration for accumulation mode particle agrees well with measurements, but it leads to a consistent underestimation of both nucleation mode and Aitken mode (dp > 100 nm) particle number concentrations. This suggests that revisions are needed in the new particle formation and growth schemes currently applied in global modeling frameworks.

scholarly journals Pan-Arctic Aerosol Number Size Distributions: Seasonality and Transport Patterns

2017 ◽  
Author(s):  
Eyal Freud ◽  
Radovan Krejci ◽  
Peter Tunved ◽  
Richard Leaitch ◽  
Quynh T. Nguyen ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Annual Cycle ◽  
Arctic Region ◽  
The Arctic ◽  
Research Station ◽  
Size Distributions ◽  
Back Trajectories ◽  
Accumulation Mode ◽  
Source Regions ◽  
The Arctic Ocean

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 inter-monthly scales. For instance, the relative occurrence of aerosol number size distributions that indicate new particle formation (NPF) event is near zero during the dark months, and increases gradually 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 (Nacc) 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 Nacc, 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 Nacc 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.

scholarly journals Multi-year statistical and modelling analysis of submicrometer aerosol number size distributions at a rain forest site in Amazonia

2018 ◽  
Author(s):  
Luciana Varanda Rizzo ◽  
Pontus Roldin ◽  
Joel Brito ◽  
John Backman ◽  
Erik Swietlicki ◽  
...  
Keyword(s):  
Particle Size ◽  
Rain Forest ◽  
Amazon Basin ◽  
Particle Number ◽  
Dry Season ◽  
Forest Site ◽  
Size Distributions ◽  
Wet Season ◽  
Accumulation Mode ◽  
Aitken Mode

Abstract. The Amazon Basin is a unique region to study atmospheric aerosols, given their relevance for the regional hydrological cycle and large uncertainty of their sources. Multi-year datasets are crucial when contrasting periods of natural conditions and periods influenced by anthropogenic emissions. In the wet season, biogenic sources and processes prevail, and the Amazonian atmospheric composition resembles pre-industrial conditions. In the dry season, the Basin is influenced by widespread biomass burning emissions. This work reports multi-year observations of high time resolution submicrometer (10–600 nm) particle number size distributions at a rain forest site in Amazonia (TT34 tower, 60 km NW from Manaus city), between years 2008–2010 and 2012–2014. Median particle number concentration was 403 cm−3 in the wet season and 1254 cm−3 in the dry season. The Aitken mode (~ 30–100 nm in diameter) was prominent during the wet season, while accumulation mode (~ 100–600 nm in diameter) dominated the particle size spectra during the dry season. Cluster analysis identified groups of aerosol number size distribution influenced by convective downdrafts, nucleation events and fresh biomass burning emissions. New particle formation and subsequent growth was rarely observed during the 749 days of observations, similar to previous observations in the Amazon Basin. A stationary 1D column model (ADCHEM – Aerosol Dynamics, gas and particle phase CHEMistry and radiative transfer model) was used to assess importance of processes behind the observed diurnal particle size distribution trends. Three major particle source types are required in the model to reproduce the observations: (i) a surface source of particles in the evening, possibly related to primary biological emissions (ii) entrainment of accumulation mode aerosols in the morning, and (iii) convective downdrafts transporting Aitken mode particles into the boundary layer mostly during the afternoon. The latter process has the largest influence on the modelled particle number size distributions. However, convective downdrafts are often associated with rain and thus act both as a source of Aitken mode particles, and as a sink of accumulation mode particles, causing a net reduction in the median total particle number concentrations in the surface layer. Our study shows that the combination of the three mentioned particle sources are essential to sustain particle number concentrations in Amazonia.

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 Advancing global aerosol simulations with size-segregated anthropogenic particle number emissions

2018 ◽  
Vol 18 (13) ◽  
pp. 10039-10054 ◽  
Author(s):  
Filippo Xausa ◽  
Pauli Paasonen ◽  
Risto Makkonen ◽  
Mikhail Arshinov ◽  
Aijun Ding ◽  
...  
Keyword(s):  
Particle Number ◽  
Climate Model ◽  
Dominant Role ◽  
Particle Diameter ◽  
Radiation Budget ◽  
Size Distributions ◽  
Anthropogenic Aerosol ◽  
Accumulation Mode ◽  
Climate Interactions ◽  
Gains Model

Abstract. Climate models are important tools that are used for generating climate change projections, in which aerosol–climate interactions are one of the main sources of uncertainties. In order to quantify aerosol–radiation and aerosol–cloud interactions, detailed input of anthropogenic aerosol number emissions is necessary. However, the anthropogenic aerosol number emissions are usually converted from the corresponding mass emissions in pre-compiled emission inventories through a very simplistic method depending uniquely on chemical composition, particle size and density, which are defined for a few, very wide main source sectors. In this work, the anthropogenic particle number emissions converted from the AeroCom mass in the ECHAM-HAM climate model were replaced with the recently formulated number emissions from the Greenhouse Gas and Air Pollution Interactions and Synergies (GAINS) model. In the GAINS model the emission number size distributions vary, for example, with respect to the fuel and technology. Special attention was paid to accumulation mode particles (particle diameter dp > 100 nm) because of (i) their capability of acting as cloud condensation nuclei (CCN), thus forming cloud droplets and affecting Earth's radiation budget, and (ii) their dominant role in forming the coagulation sink and thus limiting the concentration of sub-100 nm particles. In addition, the estimates of anthropogenic CCN formation, and thus the forcing from aerosol–climate interactions, are expected to be affected. Analysis of global particle number concentrations and size distributions reveals that GAINS implementation increases CCN concentration compared with AeroCom, with regional enhancement factors reaching values as high as 10. A comparison between modeled and observed concentrations shows that the increase in number concentration for accumulation mode particles agrees well with measurements, but it leads to a consistent underestimation of both nucleation mode and Aitken mode (dp < 100 nm) particle number concentrations. This suggests that revisions are needed in the new particle formation and growth schemes currently applied in global modeling frameworks.

scholarly journals Chemical composition and size distribution of summertime PM<sub>2.5</sub> at a high altitude remote location in the northeast of the Qinghai–Xizang (Tibet) Plateau: insights into aerosol sources and processing in free troposphere

2015 ◽  
Vol 15 (9) ◽  
pp. 5069-5081 ◽  
Author(s):  
J. Z. Xu ◽  
Q. Zhang ◽  
Z. B. Wang ◽  
G. M. Yu ◽  
X. L. Ge ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Organic Carbon ◽  
High Elevation ◽  
Water Soluble ◽  
Tibet Plateau ◽  
Size Distributions ◽  
Total Organic Nitrogen ◽  
Accumulation Mode ◽  
Average Mass ◽  
Tropospheric Aerosols

Abstract. Aerosol filter samples were collected at a high-elevation mountain observatory (4180 m a.s.l.) in the northeastern part of the Qinghai–Xizang (Tibet) Plateau (QXP) during summer 2012 using a low-volume sampler and a micro-orifice uniform deposit impactor (MOUDI). These samples were analyzed for water-soluble inorganic ions (WSIs), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and total organic nitrogen (TON) to elucidate the size-resolved chemical composition of free tropospheric aerosols in the QXP region. The average mass concentration of the sum of the analyzed species in PM2.5 (particle matter) (WSIs + OC + EC + TON) was 3.74 μg sm−3, 36% of which was sulfate, 18% OC, 17 % nitrate, 10% ammonium, 6.6% calcium, 6.4% TON, 2.6% EC, 1.5 % sodium, 0.9% chloride, 0.5% magnesium, and 0.3% potassium. The size distributions of sulfate and ammonium peaked in the accumulation mode (0.32–0.56 μm), whereas the size distributions of both nitrate and calcium peaked in the range of 1.8–3.2 μm, suggesting the formation of nitrate on mineral dust. OC, EC and TON were also predominantly found in the accumulation mode. The bulk chemical composition and the average oxidation degree of water-soluble organic matter (WSOM) were assessed using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). WSOM was found to be highly oxidized in all PM2.5 samples with an average oxygen-to-carbon atomic ratio (O / C) of 1.16 and an organic mass-to-organic carbon ratio (OM / OC) of 2.75. The highly oxidized WSOM was likely related to active cloud processing during upslope air mass transport coupled with strongly oxidizing environments caused by snow/ice photochemistry. High average ratios of OC / EC (7.6) and WSOC / OC (0.79) suggested that organic aerosols were primarily made of secondary species. Secondary organic aerosol (SOA) was estimated on average accounting for 80% (62–96%) of the PM2.5, indicating that SOA is an important component of free tropospheric aerosols over the northern QXP.

Size Distribution of Diesel Particulate Matter From a Heavy Duty Diesel Engine During FTP Transient Cycle

2004 ◽  
Author(s):  
Emre Tatli ◽  
Nigel N. Clark ◽  
Richard J. Atkinson ◽  
Gregory J. Thompson
Keyword(s):  
New York ◽  
Particulate Matter ◽  
Los Angeles ◽  
Size Distributions ◽  
Heavy Duty ◽  
Accumulation Mode ◽  
Particulate Size ◽  
Heavy Duty Diesel ◽  
Vehicle Activity ◽  
Average Size

Researchers concerned both with diesel exhaust health effects and with mechanisms of particulate matter (PM) formation have an interest in gaining understanding of PM size distributions from heavy-duty on-road diesel engines. Prior research has been done on particulate size measurement but the results fall short in understanding PM size distributions because of the response time or size range of the instruments used. This study reports the transient size distributions of PM from a 1992 Detroit Diesel Series 60 on an engine dynamometer from a full flow dilution tunnel for a FTP Transient Cycle using a Cambustion ® Differential Mobility spectrometer (DMS 500). The size bins selected for this study for the nucleation and accumulation modes were 20nm and 60nm bins, respectively. The accumulation mode during the accelerations and the nucleation mode during the decelerations were clearly observed from the distributions with respect to time. Distributions were also observed during the test cycle showing the transition between the two modes. From the results obtained from the analysis, no strong correlation between the 60nm particles and engine speed was observed even though higher counts of accumulation particles were observed at the same time that the vehicle activity occurred. Similarly, there was no correlation between the accumulation mode particles and power. When the distributions of nucleation and accumulation mode particles were plotted against each other, there was no correlation or anti-correlation. The average size distributions were also analyzed during the four periods of the FTP Transient cycle and the highest counts were observed during the Los Angeles Freeway (LAF) period. Also, higher counts at the second New York Non Freeway (NYNF) were observed during the cycle.

scholarly journals Simultaneous measurements of particle number size distributions at ground level and 260 m on a meteorological tower in urban Beijing, China

2017 ◽  
Author(s):  
Wei Du ◽  
Jian Zhao ◽  
Yuying Wang ◽  
Yingjie Zhang ◽  
Qingqing Wang ◽  
...  
Keyword(s):  
Particle Number ◽  
Ground Level ◽  
Particle Growth ◽  
Particle Formation ◽  
Size Distributions ◽  
New Particle Formation ◽  
Aerosol Composition ◽  
Accumulation Mode ◽  
Simultaneous Measurements ◽  
Emission Controls

Abstract. Despite extensive studies into characterization of particle number size distributions at ground level, real-time measurements above the urban canopy in the megacity of Beijing has never been performed to date. Here we conducted the first simultaneous measurements of size-resolved particle number concentrations at ground level and 260 m in urban Beijing from 22 August to 30 September. Our results showed overall similar temporal variations in number size distributions between ground level and 260 m, yet periods with significant differences were also observed. Particularly, accumulation mode particles were highly correlated (r2 = 0.85) at the two heights while Aitken mode particles presented more differences. Detailed analysis suggests that the vertical differences in number concentrations strongly depended on particle size, and particles with mobility diameter between 100–200 nm generally showed higher concentrations at higher altitudes. Particle growth rates and condensation sinks were also calculated which were 3.2 and 3.6 nm h−1, and 2.8 × 10−2 and 2.9 × 10−2 s−1, at ground level and 260 m, respectively. By linking particle growth with aerosol composition, we found that organics appeared to play an important role in the early stage of the growth (9:00–12:00) while sulfate was also important during the later period. Positive matrix factorization of size-resolved number concentrations identified three common sources at ground level and 260 m including a factor associated with new particle formation and growth events (NPE), and two secondary factors that represent photochemical processing and regional transport, respectively. Cooking emission was found to have a large contribution to small particles, and showed much higher concentration at ground level than 260 m at dinner time. This result has significant implications that investigation of NPE at ground level in megacities needs to consider the influences of local cooking emissions. The impacts of regional emission controls on particle number concentrations were also illustrated. Our results showed that regional emission controls have a dominant impact on accumulation mode particles by decreasing gas precursors and particulate matter loadings, and hence suppressing particle growth. In contrast, the influences on Aitken particles were much smaller due to the enhanced new particle formation (NPF) events.

scholarly journals On the seasonal variation in observed size distributions in northern Europe and their changes with decreasing anthropogenic emissions in Europe: climatology and trend analysis based on 17 years of data from Aspvreten, Sweden

2019 ◽  
Vol 19 (23) ◽  
pp. 14849-14873 ◽  
Author(s):  
Peter Tunved ◽  
Johan Ström
Keyword(s):  
Particle Number ◽  
Particle Formation ◽  
Number Concentration ◽  
Northern Europe ◽  
Anthropogenic Emissions ◽  
Particle Number Concentration ◽  
Size Distributions ◽  
Modal Number ◽  
Accumulation Mode ◽  
Aitken Mode

Abstract. Size-resolved aerosol trends were investigated based on a 17-year data set (2000–2017) from the rural background site Aspvreten located in southern Sweden (58.8∘ N, 17.4∘ E). Cluster analysis of the size distributions was performed to aid in the interpretation of the data. The results confirm previous findings of decreasing aerosol mass and number during the last decades as a result of reduced anthropogenic emissions in Europe. We show that both particle modal number concentration and size have substantially been reduced during the last 17 years. Negative trends in particle number concentration of about 10 cm−3 yr−1 are present for nuclei, Aitken, and accumulation modes. In total, integral particle number concentration has decreased by 30 %, from 1860 to ca. 1300 cm−3. The reduction in modal number concentration is accompanied by a decrease in modal size, and this decrease is largest for the accumulation mode (2 nm yr−1 or about 17 % for the whole period). These reductions have resulted in a decrease in submicron particle mass (< 390 nm) by more than 50 % over the period 2000–2017. These decreases are similar to observations found at other stations in northern Europe. Although all size classes show a downward trend as annual averages, we also show that observed trends are not evenly distributed over the year and that a rather complex picture emerges where both sign and magnitude of trends vary with season and size. The strongest negative trends are present during spring (accumulation mode) and autumn (Aitken mode). The strongest positive trends are present during summer months (Aitken mode). The combined trajectory and data analyses do not present evidence for an increase in new particle formation formed locally, although some evidence of increased new particle formation some distance away from the receptor is present. Observed aerosol size distribution data, together with an adiabatic cloud parcel model, were further used to estimate the change in cloud droplet concentration for various assumptions of updraught velocities and aerosol chemical composition. The results indicate a substantial increase in the atmospheric brightening effect due to a reduction in cloud reflectivity corresponding to 10 %–12 % reduction in cloud albedo over the period 2000–2017.

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