scholarly journals Variability of air ion concentrations in urban Paris

2015 ◽  
Vol 15 (7) ◽  
pp. 10629-10676 ◽  
Author(s):  
V. N. Dos Santos ◽  
E. Herrmann ◽  
H. E. Manninen ◽  
T. Hussein ◽  
J. Hakala ◽  
...  
Keyword(s):  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Late Summer ◽  
Particle Formation ◽  
Urban Site ◽  
New Particle Formation ◽  
Climatic Effects ◽  
Ion Concentrations ◽  
Ion Size

Abstract. Air ion concentrations influence new particle formation and consequently the global aerosol an cloud condensation nuclei loads. We aimed to evaluate air ion concentrations and characteristics of new particle formation events (NPF) in the megacity Paris, France (Megapoli project). We measured air ion number size distributions (0.8–42 nm) and fine particle number concentrations (> 6 nm) in an urban site of Paris between 26 June 2009 and 4 October 2010. Air ions were size classified as small (0.8–2 nm), intermediate (2–7 nm) and large (7–20 nm). The media concentrations of small and large ions were 670 and 680 cm−3 respectively (sum of positive an negative polarities) whereas the median concentration of intermediate ions was only 20 cm−3, as these ions were mostly present during new particle formation bursts, i.e. when gas-to-particle conversion produced fresh aerosol particles from gas phase precursors. During peaks in traffic-related particle number, the concentrations of small and intermediate ions decreased whereas the concentrations of large ions increased. Seasonal variations affected the ion population differently, with respect to their size and polarity. NPF was observed in 13 the days, being most frequent in spring and late summer (April, May, July and August). The results also suggest that NPF was favoured on the weekends in comparison to workdays, likely due to the lower levels of condensation sinks in the mornings of weekends (CS weekdays 09:00: 18 × 10−3 s−1; CS weekend 09:00: 8 × 10−3 s−1). The median growth rates (GR) of ions during the NPF events varied between 3–7 nm h−1, increasing with the ion size and being higher on workdays than on weekends for intermediate and large ions. The median GR of small ions on the other hand were rather similar on workdays and weekends. In general, NPF bursts changed the diurnal cycle of particle number, intermediate and large ions by causing an extra peak between 09:00 and 14:00. On average, during the NPF bursts the concentrations of intermediate ions were 8.5–10 times higher than on NPF non-event days, depending on the polarity, and the concentrations of large ions and particles were 1.5–1.8 and 1.2 times higher, respectively. Because the median concentrations of intermediate ions were considerably higher on NPF event days in comparison to NPF non-event days, the results indicate that intermediate ion concentrations could be used as an indication for NPF in Paris. The results suggest that NPF was a source of ions and aerosol particles in Paris and therefore contributed to both air quality degradation and climatic effects, especially in the spring and summer.

scholarly journals Variability of air ion concentrations in urban Paris

2015 ◽  
Vol 15 (23) ◽  
pp. 13717-13737 ◽  
Author(s):  
V. N. Dos Santos ◽  
E. Herrmann ◽  
H. E. Manninen ◽  
T. Hussein ◽  
J. Hakala ◽  
...  
Keyword(s):  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Late Summer ◽  
Particle Formation ◽  
Urban Site ◽  
New Particle Formation ◽  
Climatic Effects ◽  
Ion Concentrations ◽  
Ion Size

Abstract. Air ion concentrations influence new particle formation and consequently the global aerosol as potential cloud condensation nuclei. We aimed to evaluate air ion concentrations and characteristics of new particle formation events (NPF) in the megacity of Paris, France, within the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric Pollution and climate effects, and Integrated tools for assessment and mitigation) project. We measured air ion number size distributions (0.8–42 nm) with an air ion spectrometer and fine particle number concentrations (> 6 nm) with a twin differential mobility particle sizer in an urban site of Paris between 26 June 2009 and 4 October 2010. Air ions were size classified as small (0.8–2 nm), intermediate (2–7 nm), and large (7–20 nm). The median concentrations of small and large ions were 670 and 680 cm−3, respectively, (sum of positive and negative polarities), whereas the median concentration of intermediate ions was only 20 cm−3, as these ions were mostly present during new particle formation bursts, i.e. when gas-to-particle conversion produced fresh aerosol particles from gas phase precursors. During peaks in traffic-related particle number, the concentrations of small and intermediate ions decreased, whereas the concentrations of large ions increased. Seasonal variations affected the ion population differently, with respect to their size and polarity. NPF was observed in 13 % of the days, being most frequent in spring and late summer (April, May, July, and August). The results also suggest that NPF was favoured on the weekends in comparison to workdays, likely due to the lower levels of condensation sinks in the mornings of weekends (CS weekdays 09:00: 18 × 10−3 s−1; CS weekend 09:00: 8 × 10−3 s−1). The median growth rates (GR) of ions during the NPF events varied between 3 and 7 nm h−1, increasing with the ion size and being higher on workdays than on weekends for intermediate and large ions. The median GR of small ions on the other hand were rather similar on workdays and weekends. In general, NPF bursts changed the diurnal cycle of particle number as well as intermediate and large ions by causing an extra peak between 09:00 and 14:00. On average, during the NPF bursts the concentrations of intermediate ions were 8.5–10 times higher than on NPF non-event days, depending on the polarity, and the concentrations of large ions and particles were 1.5–1.8 and 1.2 times higher, respectively. Because the median concentrations of intermediate ions were considerably higher on NPF event days in comparison to NPF non-event days, the results indicate that intermediate ion concentrations could be used as an indication for NPF in Paris. The results suggest that NPF was a source of ions and aerosol particles in Paris and therefore contributed to both air quality degradation and climatic effects, especially in the spring and summer.

Studying new particle formation from chemical emissions from sea surface using  ship-borne air-sea-interaction tanks

2021 ◽  
Author(s):  
Maija Peltola ◽  
Manon Rocco ◽  
Neill Barr ◽  
Erin Dunne ◽  
James Harnwell ◽  
...  
Keyword(s):  
Marine Biology ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Chemical Species ◽  
Particle Formation ◽  
Biological Properties ◽  
The European Union ◽  
New Particle Formation ◽  
Aerosol Formation ◽  
Horizon 2020

<p>Even though oceans cover over 70% of the Earth’s surface, the ways in which oceans interact with climate are not fully known. Marine micro-organisms such as phytoplankton can play an important role in regulating climate by releasing different chemical species into air. In air these chemical species can react and form new aerosol particles. If grown to large enough sizes, aerosols can influence climate by acting as cloud condensation nuclei which influence the formation and properties of clouds. Even though a connection of marine biology and climate through aerosol formation was first proposed already over 30 years ago, the processes related to this connection are still uncertain.</p><p>To unravel how seawater properties affect aerosol formation and to identify which chemical species are responsible for aerosol formation, we built two Air-Sea-Interaction Tanks (ASIT) that isolate 1000 l of seawater and 1000 l of air directly above the water. The used seawater was collected from different locations during a ship campaign on board the R/V Tangaroa in the South West Pacific Ocean, close to Chatham Rise, east of New Zealand. Seawater from one location was kept in the tanks for 2-3 days and then changed. By using seawater collected from different locations, we could obtain water with different biological populations. To monitor the seawater, we took daily samples to determine its chemical and biological properties.</p><p>The air in the tanks was continuously flushed with particle filtered air. This way the air had on average 40 min to interact with the seawater surface before being sampled. Our air sampling was continuous and consisted of aerosol and air chemistry measurements. The instrumentation included measurements of aerosol number concentration from 1 to 500 nm and  chemical species ranging from ozone and sulphur dioxide to volatile organic compounds and chemical composition of molecular clusters.</p><p>Joining the seawater and atmospheric data together can give us an idea of what chemical species are emitted from the water into the atmosphere and whether these species can form new aerosol particles. Our preliminary results show a small number of particles in the freshly nucleated size range of 1-3 nm in the ASIT headspaces, indicating that new aerosol particles can form in the ASIT headspaces. In this presentation, we will also explore which chemical species could be responsible for aerosol formation and which plankton groups could be related to the emissions of these species. Combining these results with ambient data and modelling work can shed light on how important new particle formation from marine sources is for climate.</p><p>Acknowledgements: Sea2Cloud project is funded by European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 771369).</p>

scholarly journals Wintertime new particle formation and its contribution to cloud condensation nuclei in the Northeastern United States

2020 ◽  
Vol 20 (4) ◽  
pp. 2591-2601
Author(s):  
Fangqun Yu ◽  
Gan Luo ◽  
Arshad Arjunan Nair ◽  
James J. Schwab ◽  
James P. Sherman ◽  
...  
Keyword(s):  
United States ◽  
Particle Number ◽  
Hydrological Cycle ◽  
Cloud Condensation Nuclei ◽  
Particle Formation ◽  
New Particle Formation ◽  
Northeastern United States ◽  
Condensation Nuclei ◽  
Upper Troposphere ◽  
Inorganic Species

Abstract. Atmospheric particles can act as cloud condensation nuclei (CCN) and modify cloud properties and precipitation and thus indirectly impact the hydrological cycle and climate. New particle formation (NPF or nucleation), frequently observed at locations around the globe, is an important source of ultrafine particles and CCN in the atmosphere. In this study, wintertime NPF over the Northeastern United States (NEUS) is simulated with WRF-Chem coupled with a size-resolved (sectional) advanced particle microphysics (APM) model. Model-simulated variations in particle number concentrations during a 2-month period (November–December 2013) are in agreement with corresponding measurements taken at Pinnacle State Park (PSP), New York, and Appalachian State University (APP), North Carolina. We show that, even during wintertime, regional nucleation occurs and contributes significantly to ultrafine-particle and CCN number concentrations over the NEUS. The model shows that, due to low biogenic emissions during this period, wintertime regional nucleation is solely controlled by inorganic species and the newly developed ternary ion-mediated nucleation scheme is able to capture the variations in observed particle number concentrations (ranging from ∼200 to 20 000 cm−3) at both PSP and APP. Total particle and CCN number concentrations dramatically increase following NPF events and have the highest values over the Ohio Valley region, where elevated [SO2] is sustained by power plants. Secondary particles dominate particle number abundance over the NEUS, and their fraction increases with altitude from ≳85 % near the surface to ≳95 % in the upper troposphere. The secondary fraction of CCN also increases with altitude, from 20 %–50 % in the lower boundary layer to 50 %–60 % in the middle troposphere to 70 %–85 % in the upper troposphere.

scholarly journals New particle formation events observed at King Sejong Station, Antarctic Peninsula – Part 1: Physical characteristics and contribution to cloud condensation nuclei

2018 ◽  
Author(s):  
Jaeseok Kim ◽  
Young Jun Yoon ◽  
Yeontae Gim ◽  
Jin Hee Choi ◽  
Hyo Jin Kang ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Particle Formation ◽  
Physical Characteristics ◽  
Weddell Sea ◽  
New Particle Formation ◽  
Condensation Nuclei ◽  
Source Rate ◽  
The Mean

Abstract. The physical characteristics of aerosol particles during a particle burst observed at King Sejong Station in Antarctic Peninsula from March 2009 to December 2016 were analyzed. This study focuses on the seasonal variation in parameters related to particle formation such as the occurrence, formation rate (FR) and growth rate (GR), condensation sink (CS), and source rate of condensable vapor. The number concentrations during new particle formation (NPF) events varied from 1707 cm−3 to 83 120 cm−3, with an average of 20 649 ± 9290 cm−3, and the duration of the NPF events ranged from 0.6 h to 14.4 h, with a mean of 4.6 ± 1.5 h. The NPF event dominantly occurred during austral summer period (~ 72 %). The mean values of FR and GR of the aerosol particles were 2.79 ± 1.05 cm−3 s−1 and 0.68 ± 0.27 nm h−1, respectively showing enhanced rates in the summer season. The mean value of FR at King Sejong Station was higher than that at other sites in Antarctica, at 0.002–0.3 cm−3 s−1, while those of growth rates was relatively similar results observed by precious studies, at 0.4~4.3 nm h−1. The average values of CS and source rate of condensable vapor were (6.04 ± 2.74) × 10−3 s−1 and (5.19 ± 3.51) × 104 cm−3 s−1, respectively. The contribution of particle formation to cloud condensation nuclei (CCN) concentration was also investigated. The CCN concentration during the NPF period increased approximately 9 % compared with the background concentration. In addition, the effects of the origin and pathway of air masses on the characteristics of aerosol particles during a NPF event were determined. The FRs were similar regardless of the origin and pathway, whereas the GRs of particles originating from the Antarctic Peninsula and the Bellingshausen Sea, at 0.77 ± 0.25 nm h−1 and 0.76 ± 0.30 nm h−1, respectively, were higher than those of particles originating from the Weddell Sea (0.41 ± 0.15 nm h−1).

scholarly journals Evaluation of the contribution of new particle formation to cloud droplet in urban atmosphere

2021 ◽  
Author(s):  
Sihui Jiang ◽  
Fang Zhang ◽  
Jingye Ren ◽  
Lu Chen ◽  
Xing Yan ◽  
...  
Keyword(s):  
Water Vapor ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Cloud Droplet ◽  
Particle Formation ◽  
Urban Atmosphere ◽  
Primary Sources ◽  
New Particle Formation ◽  
Multiple Sources ◽  
Considerable Impact

Abstract. New particle formation (NPF) is a large source of cloud condensation nuclei (CCN) and cloud droplet in the troposphere. In this study, we quantified the contribution of NPF to cloud droplet number concentration (CDNC, or Nd) at typical updraft velocities (V) in clouds using a field campaign data of aerosol number size distribution and chemical composition observed on May 25–June 18, 2017 in urban Beijing. We show that the NPF drives the variations of CCN and cloud droplet and increases Nd by 30–33 % at V = 0.3–3 m s−1 in urban atmosphere. A markedly reduction in Nd is observed due to water vapor competition with consideration of actual environmental updraft velocity, decreasing by 11.8 ± 5.0 % at V = 3 m s−1 and 19.0 ± 4.5 % at V = 0.3 m s−1 compared to that from a prescribed supersaturation. The effect of water vapor competition becomes smaller at larger V that can provide more sufficient water vapor. Essentially, water vapor competition led to the reduction in Nd by decreasing the environmental maximum supersaturation (Smax) for the activation of aerosol particles. It is shown that Smax was decreased by 14.5–11.7 % for V = 0.3–3 m s−1. Particularly, the largest suppression of cloud droplet formation due to the water vapor competition is presented at extremely high aerosol particle number concentrations. As a result, although a larger increase of CCN-size particles by NPF event is derived on clean NPF day when pre-existing background aerosol particles are very low, there is no large discrepancy in the enhancement of Nd by NPF between the clean and polluted NPF day. We finally show a considerable impact of the primary sources when evaluating the NPF contribution to cloud droplet based on a case study. Our study highlights the importance of fully consideration of both the environmental meteorological conditions and multiple sources (i.e. secondary and primary) to evaluate the NPF effect on clouds and the associated climate effects in polluted regions.

scholarly journals Submicron aerosols at thirteen diversified sites in China: size distribution, new particle formation and corresponding contribution to cloud condensation nuclei production

2014 ◽  
Vol 14 (10) ◽  
pp. 15149-15189 ◽  
Author(s):  
J. F. Peng ◽  
M. Hu ◽  
Z. B. Wang ◽  
X. F. Huang ◽  
P. Kumar ◽  
...  
Keyword(s):  
Size Distribution ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Particle Formation ◽  
New Particle Formation ◽  
Condensation Nuclei ◽  
Accumulation Mode ◽  
Nucleation Mode ◽  
Secondary Formation ◽  
Urban Sites

Abstract. Understanding the particle number size distributions in diversified atmospheric environments is important in order to design mitigation strategies related to submicron particles and their effect on regional air quality, haze and human health. In this study, we conducted 15 different field measurement campaigns, each one-month long, between 2007 and 2011 at 13 individual sites in China. These were 5 urban sites, 4 regional sites, 3 coastal/background sites and one ship cruise measurement along eastern coastline of China. Size resolved particles were measured in the 15–600 nm size range. The median particle number concentrations (PNC) were found to vary in the range of 1.1–2.2 × 104 cm−3 at urban sites, 0.8–1.5 × 104 cm−3 at regional sites, 0.4–0.6 × 104 cm−3 at coastal/background sites, and 0.5 × 104 cm−3 during cruise measurements. Peak diameters at each of these sites varied greatly from 24 nm to 115 nm. Particles in the 15–25 nm (nucleation mode), 25–100 nm (Aitken mode) and 100–600 nm (accumulation mode) range showed different characteristics at each of the studied sites, indicating the features of primary emissions and secondary formation in these diversified atmospheric environments. Diurnal variations show a build-up of accumulation mode particles belt at regional sites, suggesting the contribution of regional secondary aerosol pollution. Frequencies of new particle formation (NPF) events were much higher at urban and regional sites than at coastal sites and cruise measurement. The average growth rates (GRs) of nucleation mode particles were 8.0–10.9 nm h−1 at urban sites, 7.4–13.6 nm h−1 at regional sites and 2.8–7.5 nm h−1 at both coastal and cruise measurement sites. The high gaseous precursors and strong oxidation at urban and regional sites not only favored the formation of particles, but also accelerated the growth rate of the nucleation mode particles. No significant difference in condensation sink (CS) during NPF days were observed among different site types, suggesting that the NPF events in background area were more influenced by the pollutant transport. In addition, average contributions of NPF events to potential cloud condensation nuclei (CCN) at 0.2% super-saturation in the afternoon of all sampling days were calculated as 11% and 6% at urban sites and regional sites, respectively. On the other hand, NPF events at coastal and cruise measurement sites had little impact on potential production of CCN. This study provides a large dataset of aerosol size distribution in diversified atmosphere of China, improving our general understanding of emission, secondary formation, new particles formation and corresponding CCN activity of submicron aerosols in Chinese environments.

scholarly journals Impact of temperature dependence on the possible contribution of organics to new particle formation in the atmosphere

2017 ◽  
Vol 17 (8) ◽  
pp. 4997-5005 ◽  
Author(s):  
Fangqun Yu ◽  
Gan Luo ◽  
Alexey B. Nadykto ◽  
Jason Herb
Keyword(s):  
North America ◽  
Temperature Dependence ◽  
Radiative Forcing ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Lower Troposphere ◽  
Particle Formation ◽  
Strong Impact ◽  
New Particle Formation ◽  
Aerosol Model

Abstract. Secondary particles formed via new particle formation (NPF) dominate cloud condensation nuclei (CCN) abundance in most parts of the troposphere and are important for aerosol indirect radiative forcing (IRF). Laboratory measurements have shown that certain organic compounds can significantly enhance the binary nucleation of sulfuric acid and H2O. According to our recent study comparing particle size distributions measured in nine forest areas in North America with those predicted by a global size-resolved aerosol model, current H2SO4–organics nucleation parameterizations appear to significantly overpredict NPF and particle number concentrations in summer. The lack of temperature dependence in the current H2SO4–organics nucleation parameterization has been suggested to be a possible reason for the observed overprediction. In this work, H2SO4–organics clustering thermodynamics from quantum chemical studies has been employed to develop a scheme to incorporate temperature dependence into H2SO4–organics nucleation parameterization. We show that temperature has a strong impact on H2SO4–organics nucleation rates and may reduce the nucleation rate by  ∼  1 order of magnitude per 10 K of temperature increase. The particle number concentrations in summer over North America based on the revised scheme is a factor of more than 2 lower, which is in much better agreement with the observations. With the temperature-dependent H2SO4–organics nucleation parameterization, the summer CCN concentrations in the lower troposphere in the Northern Hemisphere are about 10–30 % lower compared to the temperature-independent parameterization. This study highlights the importance of the temperature effect and its impacts on NPF in the global modeling of aerosol number abundance.

scholarly journals Particle number concentrations over Europe in 2030: the role of emissions and new particle formation

2013 ◽  
Vol 13 (20) ◽  
pp. 10271-10283 ◽  
Author(s):  
L. Ahlm ◽  
J. Julin ◽  
C. Fountoukis ◽  
S. N. Pandis ◽  
I. Riipinen
Keyword(s):  
Human Health ◽  
Particle Number ◽  
Aerosol Particles ◽  
Particle Formation ◽  
Number Concentration ◽  
Anthropogenic Emissions ◽  
Particle Number Concentration ◽  
New Particle Formation ◽  
So2 Emissions ◽  
Emission Reductions

Abstract. The aerosol particle number concentration is a key parameter when estimating impacts of aerosol particles on climate and human health. We use a three-dimensional chemical transport model with detailed microphysics, PMCAMx-UF, to simulate particle number concentrations over Europe in the year 2030, by applying emission scenarios for trace gases and primary aerosols. The scenarios are based on expected changes in anthropogenic emissions of sulfur dioxide, ammonia, nitrogen oxides, and primary aerosol particles with a diameter less than 2.5 μm (PM2.5) focusing on a photochemically active period, and the implications for other seasons are discussed. For the baseline scenario, which represents a best estimate of the evolution of anthropogenic emissions in Europe, PMCAMx-UF predicts that the total particle number concentration (Ntot) will decrease by 30–70% between 2008 and 2030. The number concentration of particles larger than 100 nm (N100), a proxy for cloud condensation nuclei (CCN) concentration, is predicted to decrease by 40–70% during the same period. The predicted decrease in Ntot is mainly a result of reduced new particle formation due to the expected reduction in SO2 emissions, whereas the predicted decrease in N100 is a result of both decreasing condensational growth and reduced primary aerosol emissions. For larger emission reductions, PMCAMx-UF predicts reductions of 60–80% in both Ntot and N100 over Europe. Sensitivity tests reveal that a reduction in SO2 emissions is far more efficient than any other emission reduction investigated, in reducing Ntot. For N100, emission reductions of both SO2 and PM2.5 contribute significantly to the reduced concentration, even though SO2 plays the dominant role once more. The impact of SO2 for both new particle formation and growth over Europe may be expected to be somewhat higher during the simulated period with high photochemical activity than during times of the year with less incoming solar radiation. The predicted reductions in both Ntot and N100 between 2008 and 2030 in this study will likely reduce both the aerosol direct and indirect effects, and limit the damaging effects of aerosol particles on human health in Europe.

scholarly journals Spring and summer contrast in new particle formation over nine forest areas in North America

2015 ◽  
Vol 15 (24) ◽  
pp. 13993-14003 ◽  
Author(s):  
F. Yu ◽  
G. Luo ◽  
S. C. Pryor ◽  
P. R. Pillai ◽  
S. H. Lee ◽  
...  
Keyword(s):  
North America ◽  
Radiative Forcing ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Formation Rate ◽  
Ultrafine Particle ◽  
Particle Formation ◽  
New Particle Formation ◽  
Forest Sites ◽  
Chamber Studies

Abstract. Recent laboratory chamber studies indicate a significant role for highly oxidized low-volatility organics in new particle formation (NPF), but the actual role of these highly oxidized low-volatility organics in atmospheric NPF remains uncertain. Here, particle size distributions (PSDs) measured in nine forest areas in North America are used to characterize the occurrence and intensity of NPF and to evaluate model simulations using an empirical formulation in which formation rate is a function of the concentrations of sulfuric acid and low-volatility organics from alpha-pinene oxidation (Nucl-Org), and using an ion-mediated nucleation mechanism (excluding organics) (Nucl-IMN). On average, NPF occurred on ~ 70 % of days during March for the four forest sites with springtime PSD measurements, while NPF occurred on only ~ 10 % of days in July for all nine forest sites. Both Nucl-Org and Nucl-IMN schemes capture the observed high frequency of NPF in spring, but the Nucl-Org scheme significantly overpredicts while the Nucl-IMN scheme slightly underpredicts NPF and particle number concentrations in summer. Statistical analyses of observed and simulated ultrafine particle number concentrations and frequency of NPF events indicate that the scheme without organics agrees better overall with observations. The two schemes predict quite different nucleation rates (including their spatial patterns), concentrations of cloud condensation nuclei, and aerosol first indirect radiative forcing in North America, highlighting the need to reduce NPF uncertainties in regional and global earth system models.

scholarly journals Spring and summer contrast in new particle formation over nine forest areas in North America

2015 ◽  
Vol 15 (15) ◽  
pp. 21271-21298 ◽  
Author(s):  
F. Yu ◽  
G. Luo ◽  
S. C. Pryor ◽  
P. R. Pillai ◽  
S. H. Lee ◽  
...  
Keyword(s):  
North America ◽  
Radiative Forcing ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Formation Rate ◽  
Ultrafine Particle ◽  
Particle Formation ◽  
New Particle Formation ◽  
Forest Sites ◽  
Chamber Studies

Abstract. Recent laboratory chamber studies indicate a significant role for highly oxidized low volatility organics in new particle formation (NPF) but the actual role of these highly oxidized low volatility organics in atmospheric NPF remains uncertain. Here, particle size distributions (PSDs) measured in nine forest areas in North America are used to characterize the occurrence and intensity of NPF and to evaluate model simulations using an empirical formulation in which formation rate is a function of the concentrations of sulfuric acid and low volatility organics from alpha-pinene oxidation (Nucl-Org), and using an ion-mediated nucleation mechanism (excluding organics; Nucl-IMN). On average, NPF occurred on ~ 70 % of days during March for the four forest sites with springtime PSD measurements, while NPF occurred on only ~ 10 % of days in July for all nine forest sites. Both Nucl-Org and Nucl-IMN schemes capture the observed high frequency of NPF in spring, but the Nucl-Org scheme significantly over-predicts while the Nucl-IMN scheme slightly under-predicts NPF and particle number concentrations in summer. Statistical analyses of observed and simulated ultrafine particle number concentrations and frequency of NPF events indicate that the scheme without organics agrees better overall with observations. The two schemes predict quite different nucleation rates (including their spatial patterns), concentrations of cloud condensation nuclei, and aerosol first indirect radiative forcing in North America, highlighting the need to reduce NPF uncertainties in regional and global earth system models.

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