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.

scholarly journals New Particle Formation and impact on CCN concentrations in the boundary layer and free troposphere at the high altitude station of Chacaltaya (5240 m a.s.l.), Bolivia

2016 ◽  
Author(s):  
C. Rose ◽  
K. Sellegri ◽  
I. Moreno ◽  
F. Velarde ◽  
M. Ramonet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Number ◽  
Particle Growth ◽  
Particle Formation ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Free Troposphere ◽  
New Particle Formation ◽  
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 contribute significantly to cloud condensation nuclei (CCN) concentrations. NPF events were frequently observed at the highest atmospheric observatory in the world, 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 January 1 and December 31 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 events relative to the transport of pre-existing particles to the site. The averaged production of 50 nm particles during those events was 5072 cm−3, 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 56 % 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.

Impact of Urban Pollution on Organic-Mediated New-Particle Formation and Particle Number Concentration in the Amazon Rainforest

2021 ◽  
Vol 55 (8) ◽  
pp. 4357-4367
Author(s):  
Bin Zhao ◽  
Jerome D. Fast ◽  
Neil M. Donahue ◽  
Manish Shrivastava ◽  
Meredith Schervish ◽  
...  
Keyword(s):  
Particle Number ◽  
Urban Pollution ◽  
Particle Formation ◽  
Number Concentration ◽  
Amazon Rainforest ◽  
Particle Number Concentration ◽  
New Particle Formation

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 Observation of new particle formation in subtropical urban environment

2011 ◽  
Vol 11 (8) ◽  
pp. 3823-3833 ◽  
Author(s):  
H. C. Cheung ◽  
L. Morawska ◽  
Z. D. Ristovski
Keyword(s):  
Growth Rate ◽  
Urban Environment ◽  
Size Distribution ◽  
Particle Number ◽  
Particle Growth ◽  
Particle Formation ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Industrial Emissions ◽  
Traffic Exhaust

Abstract. The aim of this study was to characterise the new particle formation events in a subtropical urban environment in the Southern Hemisphere. The study measured the number concentration of particles and its size distribution in Brisbane, Australia during 2009. The variation of particle number concentration and nucleation burst events were characterised as well as the particle growth rate which was first reported in urban environment of Australia. The annual average NUFP, NAitken and NNuc were 9.3×103, 3.7×103 and 5.6×103 cm−3, respectively. Weak seasonal variation in number concentration was observed. Local traffic exhaust emissions were a major contributor of the pollution (NUFP) observed in morning which was dominated by the Aitken mode particles, while particles formed by secondary formation processes contributed to the particle number concentration during afternoon. Overall, 65 nucleation burst events were identified during the study period. Nucleation burst events were classified into two groups, with and without particles growth after the burst of nucleation mode particles observed. The average particle growth rate of the nucleation events was 4.6 nm h−1 (ranged from 1.79–7.78 nm h−1). Case studies of the nucleation burst events were characterised including (i) the nucleation burst with particle growth which is associated with the particle precursor emitted from local traffic exhaust emission, (ii) the nucleation burst without particle growth which is due to the transport of industrial emissions from the coast to Brisbane city or other possible sources with unfavourable conditions which suppressed particle growth and (iii) interplay between the above two cases which demonstrated the impact of the vehicle and industrial emissions on the variation of particle number concentration and its size distribution during the same day.

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 Variation of size-segregated particle number concentrations in wintertime Beijing

2020 ◽  
Vol 20 (2) ◽  
pp. 1201-1216 ◽  
Author(s):  
Ying Zhou ◽  
Lubna Dada ◽  
Yiliang Liu ◽  
Yueyun Fu ◽  
Juha Kangasluoma ◽  
...  
Keyword(s):  
Particle Number ◽  
Particle Formation ◽  
Number Concentration ◽  
Spatial And Temporal Variability ◽  
Particle Number Concentration ◽  
New Particle Formation ◽  
Accumulation Mode ◽  
Nucleation Mode ◽  
Secondary Sources ◽  
Haze Days

Abstract. The spatial and temporal variability of the number size distribution of aerosol particles is an indicator of the dynamic behavior of Beijing's atmospheric pollution cocktail. This variation reflects the strength of different primary and secondary sources, such as traffic and new particle formation, as well as the main processes affecting the particle population. In this paper, we report size-segregated particle number concentrations observed at a newly developed Beijing station during the winter of 2018. Our measurements covered particle number size distributions over the diameter range of 1.5 nm–1 µm (cluster mode, nucleation mode, Aitken mode and accumulation mode), thus being descriptive of a major fraction of the processes taking place in the atmosphere of Beijing. Here we focus on explaining the concentration variations in the observed particle modes, by relating them to the potential aerosol sources and sinks, and on understanding the connections between these modes. We considered haze days and new particle formation event days separately. Our results show that during the new particle formation (NPF) event days increases in cluster mode particle number concentration were observed, whereas during the haze days high concentrations of accumulation mode particles were present. There was a tight connection between the cluster mode and nucleation mode on both NPF event and haze days. In addition, we correlated the particle number concentrations in different modes with concentrations of trace gases and other parameters measured at our station. Our results show that the particle number concentration in all the modes correlated with NOx, which reflects the contribution of traffic to the whole submicron size range. We also estimated the contribution of ion-induced nucleation in Beijing, and we found this contribution to be negligible.

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

2015 ◽  
Vol 15 (14) ◽  
pp. 19729-19801
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 vapors 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 were 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. Differences among the three simulations for the 40–100 nm particle diameter range are mostly associated with the timing of the peak total tendencies that shift the morning increase and afternoon decrease in particle number concentration by up to two hours. 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 Flow-induced errors in airborne in-situ measurements of aerosols and clouds

2019 ◽  
Author(s):  
Antonio Spanu ◽  
Maximilian Dollner ◽  
Josef Gasteiger ◽  
T. Paul Bui ◽  
Bernadett Weinzierl
Keyword(s):  
Particle Number ◽  
Flow Speed ◽  
Droplet Surface ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Droplet Deformation ◽  
Radiative Processes ◽  
Correction Scheme ◽  
The Impact

Abstract. Aerosols and clouds affect atmospheric radiative processes and climate in many complex ways and still pose the largest uncertainty in current estimates of the Earth’s changing energy budget. Airborne in-situ sensors such as the Cloud, Aerosol, and Precipitation Spectrometer (CAPS) or other optical spectrometers and optical array probes provide detailed information about the horizontal and vertical distribution of aerosol and cloud properties. However, flow distortions occurring at the location where these instruments are mounted on the outside of an aircraft may directly produce artifacts in detected particle number concentration and also cause droplet deformation and/or break-up during the measurement process. Several studies have investigated flow-induced errors assuming that air is incompressible. However, for fast-flying aircraft, the impact of air compressibility is no longer negligible. In this study, we combine airborne data with numerical simulations to investigate the flow around wing-mounted instruments and the induced errors for different realistic flight conditions. A correction scheme for deriving particle number concentrations from in-situ aerosol and cloud probes is proposed, and a new formula is provided for deriving the droplet volume from images taken by optical array probes, reducing errors by up to one order of magnitude. Shape distortions of liquid droplets can either be caused by errors in the speed with which the images are recorded or by aerodynamic forces acting at the droplet surface caused by changes in the airflow around the instrument. These forces can lead to the dynamic breakup of droplets causing artifacts in particle number concentration and size. Furthermore, an estimation of the critical breakup diameter, as a function of flight conditions is provided. Experimental data show that flow speed at the instrument location is smaller than the ambient flow speed. Our simulations confirm the observed difference and reveal a size-dependent impact on particle speed and concentration. This leads, on average, to a 25 % overestimation of the number concentration of particles larger than ~10 μm} diameter and causes distorted images of droplets and ice crystals if the flow values recorded at the instrument are used. With the proposed correction scheme both errors are significantly reduced by a factor 10. Although the presented correction scheme is derived for the DLR Falcon research aircraft (SALTRACE campaign) and validated for the DLR Falcon (A-LIFE campaign) and the NASA DC-8 (ATom campaign), the general conclusions hold for any fast-flying research airplane.

scholarly journals Flow-induced errors in airborne in situ measurements of aerosols and clouds

2020 ◽  
Vol 13 (4) ◽  
pp. 1963-1987 ◽  
Author(s):  
Antonio Spanu ◽  
Maximilian Dollner ◽  
Josef Gasteiger ◽  
T. Paul Bui ◽  
Bernadett Weinzierl
Keyword(s):  
Particle Number ◽  
Flow Speed ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Droplet Volume ◽  
Radiative Processes ◽  
Correction Scheme ◽  
Research Aircraft ◽  
The Impact

Abstract. Aerosols and clouds affect atmospheric radiative processes and climate in many complex ways and still pose the largest uncertainty in current estimates of the Earth's changing energy budget. Airborne in situ sensors such as the Cloud, Aerosol, and Precipitation Spectrometer (CAPS) or other optical spectrometers and optical array probes provide detailed information about the horizontal and vertical distribution of aerosol and cloud properties. However, flow distortions occurring at the location where these instruments are mounted on the outside of an aircraft may directly produce artifacts in detected particle number concentration and also cause droplet deformation and/or breakup during the measurement process. Several studies have investigated flow-induced errors assuming that air is incompressible. However, for fast-flying aircraft, the impact of air compressibility is no longer negligible. In this study, we combine airborne data with numerical simulations to investigate the flow around wing-mounted instruments and the induced errors for different realistic flight conditions. A correction scheme for deriving particle number concentrations from in situ aerosol and cloud probes is proposed, and a new formula is provided for deriving the droplet volume from images taken by optical array probes. Shape distortions of liquid droplets can either be caused by errors in the speed with which the images are recorded or by aerodynamic forces acting at the droplet surface caused by changes of the airflow when it approaches the instrument. These forces can lead to the dynamic breakup of droplets causing artifacts in particle number concentration and size. An estimation of the critical breakup diameter as a function of flight conditions is provided. Experimental data show that the flow speed at the instrument location is smaller than the ambient flow speed. Our simulations confirm the observed difference and reveal a size-dependent impact on particle speed and concentration. This leads, on average, to a 25 % overestimation of the number concentration of particles with diameters larger than 10 µm diameter and causes distorted images of droplets and ice crystals if the flow values recorded at the instrument are used. With the proposed corrections, errors of particle number concentration and droplet volume, as well as image distortions, are significantly reduced by up to 1 order of magnitude. Although the presented correction scheme is derived for the DLR Falcon research aircraft (Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) campaign) and validated for the DLR Falcon (Absorbing aerosol layers in a changing climate: aging, lifetime and dynamics mission conducted in 2017 (A-LIFE) campaign) and the NASA DC-8 (Atmospheric Tomography Mission (ATom) campaigns), the general conclusions hold for any fast-flying research aircraft.

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