scholarly journals Seasonal cycle and modal structure of particle number size distribution at Dome C, Antarctica

2013 ◽  
Vol 13 (3) ◽  
pp. 5729-5768
Author(s):  
E. Järvinen ◽  
A. Virkkula ◽  
T. Nieminen ◽  
P. P. Aalto ◽  
E. Asmi ◽  
...  
Keyword(s):  
Size Distribution ◽  
Seasonal Cycle ◽  
Particle Number ◽  
Formation Rate ◽  
Particle Growth ◽  
Particle Formation ◽  
Distribution Data ◽  
New Particle Formation ◽  
Total Particle Number ◽  
Total Particle

Abstract. We studied new particle formation and modal behavior of ultrafine aerosol particles on the high Antarctic East-Plateau at the Concordia station, Dome C (75°06' S, 123°23' E). Aerosol particle number size distributions were measured in the size range 10–600 nm from 14 December 2007 to 7 November 2009. We used an automatic algorithm for fitting up to three modes to the size distribution data. The total particle number concentration was low with the median of 109 cm−3. There was a clear seasonal cycle in the total particle number and the volume concentrations. The concentrations were at their highest during the austral summer with the median values of 260 cm−3 and 0.086 μm3 cm−3, and at their lowest during the austral winter with corresponding values of 15 cm−3 and 0.009 μm3 cm−3. New particle formation events were determined from the size distribution data. During the measurement period, new particle formation was seen on 80 days and for 15 of these days the particle growth rates from 10 to 25 nm size could be determined. The median particle growth rate during all these events was 2.5 nm h−1 and the median formation rate of 10 nm particles was 0.023 cm−3 s−1. Most of the events were similar to those observed in other continental locations, yet also some variability in event types was observed. Exceptional features in Dome C were the winter events that occurred during dark periods, as well as the events for which the growth could be followed during several consecutive days. We called these latter events as slowly-growing events. This paper is the first one to analyze long-term size distribution data from Dome C, and also the first paper to show that new particle formation events occur in the central Antarctica.

scholarly journals Seasonal cycle and modal structure of particle number size distribution at Dome C, Antarctica

2013 ◽  
Vol 13 (15) ◽  
pp. 7473-7487 ◽  
Author(s):  
E. Järvinen ◽  
A. Virkkula ◽  
T. Nieminen ◽  
P. P. Aalto ◽  
E. Asmi ◽  
...  
Keyword(s):  
Size Distribution ◽  
Seasonal Cycle ◽  
Particle Number ◽  
Formation Rate ◽  
Particle Growth ◽  
Particle Formation ◽  
Distribution Data ◽  
New Particle Formation ◽  
Total Particle Number ◽  
Total Particle

Abstract. We studied new particle formation and modal behavior of ultrafine aerosol particles on the high East Antarctic plateau at the Concordia station, Dome C (75°06' S, 123°23' E). Aerosol particle number size distributions were measured in the size range 10–600 nm from 14 December 2007 to 7 November 2009. We used an automatic algorithm for fitting up to three modes to the size distribution data. The total particle number concentration was low with the median of 109 cm−3. There was a clear seasonal cycle in the total particle number and the volume concentrations. The concentrations were at their highest during the austral summer with the median values of 260 cm−3 and 0.086 μm3 cm−3, and at their lowest during the austral winter with corresponding values of 15 cm−3 and 0.009 μm3 cm−3. New particle formation events were determined from the size distribution data. During the measurement period, natural new particle formation was observed on 60 days and for 15 of these days the particle growth rates from 10 to 25 nm in size could be determined. The median particle growth rate during all these events was 2.5 nm h−1 and the median formation rate of 10 nm particles was 0.023 cm−3 s−1. Most of the events were similar to those observed at other continental locations, yet also some variability in event types was observed. Exceptional features in Dome C were the winter events that occurred during dark periods, as well as the events for which the growth could be followed during several consecutive days. We called these latter events slowly growing events. This paper is the first one to analyze long-term size distribution data from Dome C, and also the first paper to show that new particle formation events occur in central Antarctica.

scholarly journals Production, growth and properties of ultrafine atmospheric aerosol particles in an urban environment

2011 ◽  
Vol 11 (3) ◽  
pp. 1339-1353 ◽  
Author(s):  
I. Salma ◽  
T. Borsós ◽  
T. Weidinger ◽  
P. Aalto ◽  
T. Hussein ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Atmospheric Aerosol ◽  
Particle Number ◽  
Aerosol Particles ◽  
Formation Rate ◽  
Particle Formation ◽  
Number Concentration ◽  
New Particle Formation ◽  
Total Particle Number ◽  
Total Particle

Abstract. Number concentrations of atmospheric aerosol particles were measured by a flow-switching type differential mobility particle sizer in an electrical mobility diameter range of 6–1000 nm in 30 channels near central Budapest with a time resolution of 10 min continuously from 3 November 2008 to 2 November 2009. Daily median number concentrations of particles varied from 3.8 × 103 to 29 ×103 cm−3 with a yearly median of 11.8 × 103 cm−3. Contribution of ultrafine particles to the total particle number ranged from 58 to 92% with a mean ratio and standard deviation of (79 ± 6)%. Typical diurnal variation of the particle number concentration was related to the major emission patterns in cities, new particle formation, sinks of particles and meteorology. Shapes of the monthly mean number size distributions were similar to each other. Overall mean for the number median mobility diameter of the Aitken and accumulation modes were 26 and 93 nm, respectively, which are substantially smaller than for rural or background environments. The Aitken and accumulation modes contributed similarly to the total particle number concentrations at the actual measurement location. New particle formation and growth unambiguously occurred on 83 days, which represent 27% of all relevant days. Hence, new particle formation and growth are not rare phenomena in Budapest. Their frequency showed an apparent seasonal variation with a minimum of 7.3% in winter and a maximum of 44% in spring. New particle formation events were linked to increased gas-phase H2SO4 concentrations. In the studied area, new particle formation is mainly affected by condensation sink and solar radiation. The formation process seems to be not sensitive to SO2, which was present in a yearly median concentration of 6.7 μg m−3. This suggests that the precursor gas was always available in excess. Formation rate of particles with a diameter of 6 nm varied between 1.65 and 12.5 cm−3 s−1 with a mean and standard deviation of (4.2 ± 2.5) cm−3 s−1. Seasonal dependency for the formation rate could not be identified. Growth curves of nucleated particles were usually superimposed on the characteristic diurnal pattern of road traffic direct emissions. The growth rate of the nucleation mode with a median diameter of 6 nm varied from 2.0 to 13.3 nm h−1 with a mean and standard deviation of (7.7 ± 2.4) nm h−1. There was an indicative tendency for larger growth rates in summer and for smaller values in winter. New particle formation events increased the total number concentration by a mean factor and standard deviation of 2.3 ± 1.1 relative to the concentration that occurred immediately before the event. Several indirect evidences suggest that the new particle formation events occurred at least over the whole city, and were of regional type. The results and conclusions presented are the first information of this kind for the region over one-year long time period.

scholarly journals Basic characteristics of atmospheric particles, trace gases and meteorology in a relatively clean Southern African Savannah environment

2008 ◽  
Vol 8 (2) ◽  
pp. 6313-6353 ◽  
Author(s):  
L. Laakso ◽  
H. Laakso ◽  
P. P. Aalto ◽  
P. Keronen ◽  
T. Petäjä ◽  
...  
Keyword(s):  
Growth Rates ◽  
Cloud Condensation Nuclei ◽  
Regional Climate ◽  
Formation Rate ◽  
Measurement Data ◽  
Particle Growth ◽  
Particle Formation ◽  
New Particle Formation ◽  
Total Particle ◽  
Pm2.5 And Pm10

Abstract. We have analyzed one year (July 2006–July 2007) of measurement data from a relatively clean background site located in dry savannah in South Africa. The annual-median trace gas concentrations were equal to 0.7 ppb for SO2, 1.4 ppb for NOx, 36 ppb for O3 and 105 ppb for CO. The corresponding PM1, PM2.5 and PM10 concentrations were 9.0, 10.5 and 18.8 μg m−3, and the annual median total particle number concentration in the size range 10–840 nm was 2340 cm−3. Gases and particles had a clear seasonal and diurnal variation, which was associated with field fires and biological activity together with local meteorology. Atmospheric new-particle formation was observed to take place in more than 90% of the analyzed days. The days with no new particle formation were cloudy or rainy days. The formation rate of 10 nm particles varied in the range of 0.1–28 cm−3 s−1 (median 1.9 cm−3 s−1) and nucleation mode particle growth rates were in the range 3–21 nm h−1 (median 8.5 nm h−1). Due to high formation and growth rates, observed new particle formation gives a significant contribute to the number of cloud condensation nuclei budget, having a potential to affect the regional climate forcing patterns.

scholarly journals The contribution of boundary layer nucleation events to total particle concentrations on regional and global scales

2006 ◽  
Vol 6 (12) ◽  
pp. 5631-5648 ◽  
Author(s):  
D. V. Spracklen ◽  
K. S. Carslaw ◽  
M. Kulmala ◽  
V.-M. Kerminen ◽  
G. W. Mann ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sulfuric Acid ◽  
Particle Number ◽  
Formation Rate ◽  
Particle Surface ◽  
Particle Formation ◽  
New Particle Formation ◽  
Particle Surface Area ◽  
Primary Particles ◽  
Total Particle

Abstract. The contribution of boundary layer (BL) nucleation events to total particle concentrations on the global scale has been studied by including a new particle formation mechanism in a global aerosol microphysics model. The mechanism is based on an analysis of extensive observations of particle formation in the BL at a continental surface site. It assumes that molecular clusters form at a rate proportional to the gaseous sulfuric acid concentration to the power of 1. The formation rate of 3 nm diameter observable particles is controlled by the cluster formation rate and the existing particle surface area, which acts to scavenge condensable gases and clusters during growth. Modelled sulfuric acid vapour concentrations, particle formation rates, growth rates, coagulation loss rates, peak particle concentrations, and the daily timing of events in the global model agree well with observations made during a 22-day period of March 2003 at the SMEAR II station in Hyytiälä, Finland. The nucleation bursts produce total particle concentrations (>3 nm diameter) often exceeding 104 cm−3, which are sustained for a period of several hours around local midday. The predicted global distribution of particle formation events broadly agrees with what is expected from available observations. Over relatively clean remote continental locations formation events can sustain mean total particle concentrations up to a factor of 8 greater than those resulting from anthropogenic sources of primary organic and black carbon particles. However, in polluted continental regions anthropogenic primary particles dominate particle number and formation events lead to smaller enhancements of up to a factor of 2. Our results therefore suggest that particle concentrations in remote continental regions are dominated by nucleated particles while concentrations in polluted continental regions are dominated by primary particles. The effect of BL particle formation over tropical regions and the Amazon is negligible. These first global particle formation simulations reveal some interesting sensitivities. We show, for example, that significant reductions in primary particle emissions may lead to an increase in total particle concentration because of the coupling between particle surface area and the rate of new particle formation. This result suggests that changes in emissions may have a complicated effect on global and regional aerosol properties. Overall, our results show that new particle formation is a significant component of the aerosol particle number budget.

scholarly journals Modelling the contribution of biogenic VOCs to new particle formation in the Jülich plant atmosphere chamber

2014 ◽  
Vol 14 (20) ◽  
pp. 27973-28018 ◽  
Author(s):  
L. Liao ◽  
M. Dal Maso ◽  
D. Mogensen ◽  
P. Roldin ◽  
A. Rusanen ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Particle Number ◽  
Particle Formation ◽  
Oxidation Products ◽  
New Particle Formation ◽  
Particle Volume ◽  
Aerosol Dynamics ◽  
Total Particle Number ◽  
Total Particle ◽  
Air Chemistry

Abstract. We used the MALTE-BOX model including near-explicit air chemistry and detailed aerosol dynamics to study the mechanisms of observed new particle formation events in the Jülich Plant Atmosphere Chamber. The modelled and measured H2SO4 (sulfuric acid) concentrations agreed within a factor of two. The modelled total monoterpene concentration was in line with PTR-MS observations, and we provided the distributions of individual isomers of terpenes, when no measurements were available. The aerosol dynamic results supported the hypothesis that H2SO4 is one of the critical compounds in the nucleation process. However, compared to kinetic H2SO4 nucleation, nucleation involving OH oxidation products of monoterpenes showed a better agreement with the measurements, with R2 up to 0.97 between modelled and measured total particle number concentrations. The nucleation coefficient for kinetic H2SO4 nucleation was 2.1 × 10−11 cm3 s−1, while the organic nucleation coefficient was 9.0 × 10−14 cm3 s−1. We classified the VOC oxidation products into two sub-groups including extremely low-volatility organic compounds (ELVOCs) and semi-volatile organic compounds (SVOCs). These ELVOCs and SVOCs contributed approximately equally to the particle volume production, whereas only ELVOCs made the smallest particles to grow in size. The model simulations revealed that the chamber walls constitute a major net sink of SVOCs on the first experiment day. However, the net wall SVOC uptake was gradually reduced because of SVOC desorption during the following days. Thus, in order to capture the observed temporal evolution of the particle number size distribution, the model needs to consider reversible gas-wall partitioning.

scholarly journals The contribution of boundary layer nucleation events to total particle concentrations on regional and global scales

2006 ◽  
Vol 6 (4) ◽  
pp. 7323-7368 ◽  
Author(s):  
D. V. Spracklen ◽  
K. S. Carslaw ◽  
M. Kulmala ◽  
V.-M. Kerminen ◽  
G. W. Mann ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Number ◽  
Marine Boundary Layer ◽  
Formation Rate ◽  
Particle Surface ◽  
Particle Formation ◽  
New Particle Formation ◽  
Particle Surface Area ◽  
Primary Particles ◽  
Total Particle

Abstract. The contribution of boundary layer nucleation events to total particle concentrations on the global scale has been studied by including a new particle formation mechanism in a global aerosol microphysics model. The mechanism is based on an analysis of extensive observations of particle formation in the boundary layer at a continental surface site. It assumes that molecular clusters form at a rate proportional to the gaseous sulfuric acid concentration to the power of 1. The formation rate of 3 nm diameter observable particles is controlled by the cluster formation rate and the existing particle surface area, which acts to scavenge condensable gases and clusters during growth. Modelled sulfuric acid vapour concentrations, particle formation rates, growth rates, coagulation loss rates, peak particle concentrations, and the daily timing of events in the global model agree well with observations made during a 22-day period of March 2003 at the SMEAR II station in Hyytiälä, Finland. The nucleation bursts produce total particle concentrations (>3 nm diameter) often exceeding 104 cm−3, which are sustained for a period of several hours around local midday. The predicted global distribution of particle formation events broadly agrees with what is expected from available observations. Over relatively clean remote continental locations formation events can sustain mean total particle concentrations up to a factor of 8 greater than those resulting from anthropogenic sources of primary organic and black carbon particles. However, in polluted continental regions anthropogenic primary particles dominate particle number and formation events lead to smaller enhancements of up to a factor of 2. Our results therefore suggest that particle concentrations in remote continental are dominated by nucleated particles while concentrations in polluted continental regions are dominated by primary particles. The effect of boundary layer particle formation over tropical regions and the Amazon is negligible. Particle concentrations are enhanced by a factor 3–10 over the remote Southern Ocean (30–70° S), resulting in total concentrations of ~250–1000 cm−3, in good agreement with observations. Particle formation tends to peak towards the top of the marine boundary layer and there is a lack of obvious burst-like behaviour at the sea surface. This result suggests that new particle formation in the marine boundary layer could be confused with entrainment from the free troposphere. These first global particle formation simulations reveal some interesting sensitivities. We show, for example, that significant reductions in primary particle emissions may lead to an increase in total particle concentration because of the coupling between particle surface area and the rate of new particle formation. This result suggests that changes in emissions may have a complicated effect on global and regional aerosol properties. Overall, our results show that new particle formation is a significant component of the aerosol particle number budget.

scholarly journals Basic characteristics of atmospheric particles, trace gases and meteorology in a relatively clean Southern African Savannah environment

2008 ◽  
Vol 8 (16) ◽  
pp. 4823-4839 ◽  
Author(s):  
L. Laakso ◽  
H. Laakso ◽  
P. P. Aalto ◽  
P. Keronen ◽  
T. Petäjä ◽  
...  
Keyword(s):  
Growth Rates ◽  
Cloud Condensation Nuclei ◽  
Regional Climate ◽  
Formation Rate ◽  
Measurement Data ◽  
Particle Growth ◽  
Particle Formation ◽  
New Particle Formation ◽  
Total Particle ◽  
Pm2.5 And Pm10

Abstract. We have analyzed one year (July 2006–July 2007) of measurement data from a relatively clean background site located in dry savannah in South Africa. The annual-median trace gas concentrations were equal to 0.7 ppb for SO2, 1.4 ppb for NOx, 36 ppb for O3 and 105 ppb for CO. The corresponding PM1, PM2.5 and PM10 concentrations were 9.0, 10.5 and 18.8 μg m−3, and the annual median total particle number concentration in the size range 10–840 nm was 2340 cm−3. During Easterly winds, influence of industrial sources approximately 150 km away from the measurement site was clearly visible, especially in SO2 and NOx concentrations. Of gases, NOx and CO had a clear annual, and SO2, NOx and O3 clear diurnal cycle. Atmospheric new-particle formation was observed to take place in more than 90% of the analyzed days. The days with no new particle formation were cloudy or rainy days. The formation rate of 10 nm particles varied in the range of 0.1–28 cm−3 s−1 (median 1.9 cm−3 s−1) and nucleation mode particle growth rates were in the range 3–21 nm h−1 (median 8.5 nm h−1). Due to high formation and growth rates, observed new particle formation gives a significant contribute to the number of cloud condensation nuclei budget, having a potential to affect the regional climate forcing patterns.

scholarly journals Aerosols and nucleation in Eastern China: first insights from the new SORPES-Station

2013 ◽  
Vol 13 (8) ◽  
pp. 22337-22381 ◽  
Author(s):  
E. Herrmann ◽  
A. J. Ding ◽  
V.-M. Kerminen ◽  
T. Petäjä ◽  
X. Q. Yang ◽  
...  
Keyword(s):  
Meteorological Data ◽  
Eastern China ◽  
Formation Rate ◽  
Particle Growth ◽  
Yangtze River Delta ◽  
Particle Formation ◽  
Accurate Estimate ◽  
New Particle Formation ◽  
Total Particle ◽  
The Mean

Abstract. Aerosols and new particle formation were studied in the western part of the Yangtze River Delta (YRD), at the SORPES station of Nanjing University. Air ions in the diameter range 0.8–42 nm were measured using an air ion spectrometer, and a DMPS provided particle number size distributions between 6 and 800 nm. Additionally, meteorological data, trace gas concentrations, and PM2.5 values were recorded. During the measurement period from 18 November 2011 to 31 March 2012, the mean total particle concentration was found to be 23 000 cm−3. The mean PM2.5 value was 90 μg m−3, well above national limits. During the observations, 26 new particle formation events occurred, producing 6 nm particles at a rate of about 1 cm−3 s−1. Typical particle growth rates were between 6 and 7 nm h−1. Ion measurements showed the typical cluster band below 2 nm, with total ion concentrations roughly between 600 and 1000 cm−3. A peculiar feature of the ion measurements were heightened ion cluster concentrations during the nights before event days. At 2 nm, the formation rate of charged particles was only about 0.2% of the total rate, pointing towards an only marginal role of ion-induced nucleation. Based on observations, a simple empirical criterion was deducted to estimate particle formation probability. Dominated by radiation and relative humidity, the criterion can predict the occurrence of particle formation with a 90% accuracy. In a similar fashion, a reasonably accurate estimate of particle formation rates was derived. Combined, these parameters allow for a description of particle formation based on a few basic measured variables.

scholarly journals Modeling particle nucleation and growth over northern California during the 2010 CARES campaign

2015 ◽  
Vol 15 (21) ◽  
pp. 12283-12313 ◽  
Author(s):  
A. Lupascu ◽  
R. Easter ◽  
R. Zaveri ◽  
M. Shrivastava ◽  
M. Pekour ◽  
...  
Keyword(s):  
Size Distribution ◽  
Particle Number ◽  
Particle Formation ◽  
Number Concentration ◽  
Aerosol Size Distribution ◽  
Particle Nucleation ◽  
Particle Number Concentration ◽  
New Particle Formation ◽  
Organic Vapors ◽  
Diurnal Variability

Abstract. Accurate representation of the aerosol lifecycle requires adequate modeling of the particle number concentration and size distribution in addition to their mass, which is often the focus of aerosol modeling studies. This paper compares particle number concentrations and size distributions as predicted by three empirical nucleation parameterizations in the Weather Research and Forecast coupled with chemistry (WRF-Chem) regional model using 20 discrete size bins ranging from 1 nm to 10 μm. Two of the parameterizations are based on H2SO4, while one is based on both H2SO4 and organic vapors. Budget diagnostic terms for transport, dry deposition, emissions, condensational growth, nucleation, and coagulation of aerosol particles have been added to the model and are used to analyze the differences in how the new particle formation parameterizations influence the evolving aerosol size distribution. The simulations are evaluated using measurements collected at surface sites and from a research aircraft during the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted in the vicinity of Sacramento, California. While all three parameterizations captured the temporal variation of the size distribution during observed nucleation events as well as the spatial variability in aerosol number, all overestimated by up to a factor of 2.5 the total particle number concentration for particle diameters greater than 10 nm. Using the budget diagnostic terms, we demonstrate that the combined H2SO4 and low-volatility organic vapor parameterization leads to a different diurnal variability of new particle formation and growth to larger sizes compared to the parameterizations based on only H2SO4. At the CARES urban ground site, peak nucleation rates are predicted to occur around 12:00 Pacific (local) standard time (PST) for the H2SO4 parameterizations, whereas the highest rates were predicted at 08:00 and 16:00 PST when low-volatility organic gases are included in the parameterization. This can be explained by higher anthropogenic emissions of organic vapors at these times as well as lower boundary-layer heights that reduce vertical mixing. The higher nucleation rates in the H2SO4-organic parameterization at these times were largely offset by losses due to coagulation. Despite the different budget terms for ultrafine particles, the 10–40 nm diameter particle number concentrations from all three parameterizations increased from 10:00 to 14:00 PST and then decreased later in the afternoon, consistent with changes in the observed size and number distribution. We found that newly formed particles could explain up to 20–30 % of predicted cloud condensation nuclei at 0.5 % supersaturation, depending on location and the specific nucleation parameterization. A sensitivity simulation using 12 discrete size bins ranging from 1 nm to 10 μm diameter gave a reasonable estimate of particle number and size distribution compared to the 20 size bin simulation, while reducing the associated computational cost by ~ 36 %.

scholarly journals CCN production by new particle formation in the free troposphere

2017 ◽  
Vol 17 (2) ◽  
pp. 1529-1541 ◽  
Author(s):  
Clémence Rose ◽  
Karine Sellegri ◽  
Isabel Moreno ◽  
Fernando Velarde ◽  
Michel Ramonet ◽  
...  
Keyword(s):  
Particle Number ◽  
Particle Growth ◽  
Particle Formation ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Free Troposphere ◽  
New Particle Formation ◽  
Data Set ◽  
Radiative Processes ◽  
The Impact

Abstract. Global models predict that new particle formation (NPF) is, in some environments, responsible for a substantial fraction of the total atmospheric particle number concentration and subsequently contributes significantly to cloud condensation nuclei (CCN) concentrations. NPF events were frequently observed at the highest atmospheric observatory in the world, on Chacaltaya (5240 m a.s.l.), Bolivia. The present study focuses on the impact of NPF on CCN population. Neutral cluster and Air Ion Spectrometer and mobility particle size spectrometer measurements were simultaneously used to follow the growth of particles from cluster sizes down to ∼ 2 nm up to CCN threshold sizes set to 50, 80 and 100 nm. Using measurements performed between 1 January and 31 December 2012, we found that 61 % of the 94 analysed events showed a clear particle growth and significant enhancement of the CCN-relevant particle number concentration. We evaluated the contribution of NPF, relative to the transport and growth of pre-existing particles, to CCN size. The averaged production of 50 nm particles during those events was 5072, and 1481 cm−3 for 100 nm particles, with a larger contribution of NPF compared to transport, especially during the wet season. The data set was further segregated into boundary layer (BL) and free troposphere (FT) conditions at the site. The NPF frequency of occurrence was higher in the BL (48 %) compared to the FT (39 %). Particle condensational growth was more frequently observed for events initiated in the FT, but on average faster for those initiated in the BL, when the amount of condensable species was most probably larger. As a result, the potential to form new CCN was higher for events initiated in the BL (67 % against 53 % in the FT). In contrast, higher CCN number concentration increases were found when the NPF process initially occurred in the FT, under less polluted conditions. This work highlights the competition between particle growth and the removal of freshly nucleated particles by coagulation processes. The results support model predictions which suggest that NPF is an effective source of CCN in some environments, and thus may influence regional climate through cloud-related radiative processes.

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