The role of the particle size distribution in assessing aerosol composition effects on simulated droplet activation

Abstract. Variations in the chemical composition of atmospheric aerosols alter their hygroscopicity and can lead to changes in the cloud-active fraction of the aerosols, or cloud condensation nuclei (CCN) number concentration. To investigate the importance of this effect under different atmospheric conditions, cloud droplet formation was simulated with a Lagrangian parcel model. Initial values of updraft speed and temperature were systematically varied along with aerosol number concentration, size and hygroscopicity (represented by the hygroscopicity parameter, κ). A previous study classifies the sensitivity of CCN activity to compositional changes based on the supersaturation reached in the parcel model. We found that these classifications could not be generalized to a range of aerosol size distribution median radii. Instead, variations in sensitivity with size depend on the location of the dry critical radius for droplet activation relative to the size distribution median radius. The parcel model output was used to construct droplet activation lookup tables based on κ that were implemented in the Regional Atmospheric Modeling System (RAMS) microphysical scheme. As a first application of this system, aerosol hygroscopicity and size were varied in a series of RAMS mesoscale simulations designed to investigate the sensitivity of a mixed-phase orographic cloud case to the parameter variations. Observations from a recent field campaign in northwestern Colorado provided the basis for the aerosol field initializations. Model results show moderate sensitivity in the distribution of total case precipitation to extreme changes in κ, and minimal sensitivity to observed changes in estimated κ. The impact of varying aerosol hygroscopicity diminished with increasing median radius, as expected from the parcel model results. The conclusions drawn from these simulations could simplify similar research in other cloud regimes by defining the need, or lack of need, for detailed knowledge of aerosol composition.

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The role of the particle size distribution in assessing aerosol composition effects on simulated droplet activation

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-5435-2010 ◽

2010 ◽

Vol 10 (12) ◽

pp. 5435-5447 ◽

Cited By ~ 30

Author(s):

D. S. Ward ◽

T. Eidhammer ◽

W. R. Cotton ◽

S. M. Kreidenweis

Keyword(s):

Size Distribution ◽

Cloud Condensation Nuclei ◽

Atmospheric Modeling ◽

Number Concentration ◽

Aerosol Size Distribution ◽

Detailed Knowledge ◽

Aerosol Composition ◽

Droplet Activation ◽

The Impact ◽

Aerosol Hygroscopicity

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Impact of aerosol composition on cloud condensation nuclei activity

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-3783-2012 ◽

2012 ◽

Vol 12 (8) ◽

pp. 3783-3790 ◽

Cited By ~ 28

Author(s):

Q. Zhang ◽

J. Meng ◽

J. Quan ◽

Y. Gao ◽

D. Zhao ◽

...

Keyword(s):

Size Distribution ◽

Field Experiments ◽

Cloud Condensation Nuclei ◽

Diffusion Chamber ◽

Aerosol Size Distribution ◽

Condensation Nuclei ◽

Aerosol Composition ◽

Rate Of Increase ◽

The Impact ◽

Ccn Activity

Abstract. The impact of aerosol composition on cloud condensation nuclei (CCN) activity were analyzed in this study based on field experiments carried out at downtown Tianjin, China in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS) of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC), whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%), and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5±2.6% to 12.8±6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reached up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7±19.0% to 46.5±12.3% correspondingly. The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlated well with observed NCCN at high SS (0.4%), but this consistence decreased with the falling of SS. The slopes of linear fitted lines between calculated and observed NCCN are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4% respectively. Moreover, the stand deviation (SD) of calculated NCCN increased with the decreasing of SS. A case study of CCN closure analyses indicated that the calculated error of NCCN could reach up to 34% at SS of 0.1% if aerosol composition were not included, and the calculated error decreased with the raising of SS. It is decreased to 9% at SS of 0.2%, and further decreased to 4% at SS of 0.4%.

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Impact of aerosol composition on cloud condensation nuclei activity

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-1493-2012 ◽

2012 ◽

Vol 12 (1) ◽

pp. 1493-1516

Author(s):

Q. Zhang ◽

J. Meng ◽

J. Quan ◽

Y. Gao ◽

D. Zhao ◽

...

Keyword(s):

Size Distribution ◽

Field Experiments ◽

Cloud Condensation Nuclei ◽

Diffusion Chamber ◽

Aerosol Size Distribution ◽

Condensation Nuclei ◽

Aerosol Composition ◽

Rate Of Increase ◽

The Impact ◽

Ccn Activity

Abstract. The impact of aerosol composition on cloud condensation nuclei (CCN) activity was analyzed in this study based on field experiments carried out at downtown Tianjin, China, in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS) of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC), whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%), and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5 ± 2.6% to 12.8 ± 6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reaches up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7 ± 19.0% to 46.5 ± 12.3%, correspondingly. The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlates well with observed NCCN at high SS (0.4%), but this correlation decreases with the falling of SS. The slopes of linear fitted lines between calculated and observed NCCN are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4%, respectively. Moreover, the standard deviation (SD) of calculated NCCN increases with the decreasing of SS. A case study of CCN closure analyses indicates that the calculated error of NCCN can reach up to 34% at SS of 0.1% if aerosol composition is not included, and the calculated error decreases with the raising of SS. It decreases to 9% at SS of 0.2%, and further decreases to 4% at SS of 0.4%.

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Aerosol size distribution seasonal characteristics measured in Tiksi, Russian Arctic

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-18109-2015 ◽

2015 ◽

Vol 15 (13) ◽

pp. 18109-18149 ◽

Cited By ~ 1

Author(s):

E. Asmi ◽

V. Kondratyev ◽

D. Brus ◽

T. Laurila ◽

H. Lihavainen ◽

...

Keyword(s):

Size Distribution ◽

Forest Fires ◽

Cloud Condensation Nuclei ◽

Source Region ◽

Local Maximum ◽

Aerosol Size Distribution ◽

Aerosol Composition ◽

Aerosol Sources ◽

The Impact ◽

Mass Concentrations

Abstract. Four years of continuous aerosol number size distribution measurements from an Arctic Climate Observatory in Tiksi Russia are analyzed. Source region effects on particle modal features, and number and mass concentrations are presented for different seasons. The monthly median total aerosol number concentration in Tiksi ranges from 184 cm-3 in November to 724 cm-3 in July with a local maximum in March of 481 cm-3. The total mass concentration has a distinct maximum in February–March of 1.72–2.38 μg m-3 and two minimums in June of 0.42 μg m-3 and in September–October of 0.36–0.57 μg m-3. These seasonal cycles in number and mass concentrations are related to isolated aerosol sources such as Arctic haze in early spring which increases accumulation and coarse mode numbers, and biogenic emissions in summer which affects the smaller, nucleation and Aitken mode particles. The impact of temperature dependent natural emissions on aerosol and cloud condensation nuclei numbers was significant. Therefore, in addition to the precursor emissions of biogenic volatile organic compounds, the frequent Siberian forest fires, although far are suggested to play a role in Arctic aerosol composition during the warmest months. During calm and cold months aerosol concentrations were occasionally increased by nearby aerosol sources in trapping inversions. These results provide valuable information on inter-annual cycles and sources of Arctic aerosols.

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Measured and modelled Cloud Condensation Nuclei (CCN) concentration in São Paulo, Brazil: the importance of aerosol size-resolved chemical composition on CCN concentration prediction

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-32353-2013 ◽

2013 ◽

Vol 13 (12) ◽

pp. 32353-32389 ◽

Cited By ~ 1

Author(s):

G. P. Almeida ◽

J. Brito ◽

C. A. Morales ◽

M. F. Andrade ◽

P. Artaxo

Keyword(s):

Chemical Composition ◽

Real Time ◽

Cloud Condensation Nuclei ◽

Bulk Composition ◽

Sao Paulo ◽

Aerosol Size Distribution ◽

São Paulo ◽

Condensation Nuclei ◽

Aerosol Composition ◽

The Impact

Abstract. Measurements of cloud condensation nuclei (CCN), aerosol size distribution and non-refractory chemical composition were performed from 16 to 31 October 2012 in the São Paulo Metropolitan Area (SPMA), Brazil. CCN measurements were performed at 0.2%, 0.4%, 0.6%, 0.8% and 1.0% water supersaturation and were subsequently compared with Köhler theory, considering the chemical composition. Real-time chemical composition has been obtained deploying for the first time in SPMA an Aerosol Chemical Ionization Monitor (ACSM). CCN closure analyses were performed considering internal mixture. Average aerosol composition during the studied period yielded 4.81 ± 3.05, 3.26 ± 2.10, 0.30 ± 0.27, 0.52 ± 0.32, 0.37 ± 0.21 and 0.04 ± 0.04 μg m−3 for organics, BC, NH4, SO4, NO3 and Cl, respectively. Particle number concentration was 12 813 ± 5350 cm−3, being a large fraction in the nucleation mode. CCN concentrations were on average 1090 ± 328 cm−3 and 3570 ± 1695 cm−3 at SS = 0.2% and SS = 1.0%, respectively. Results show an increase in aerosol hygroscopicity in the afternoon as a result of aerosol photochemical processing, leading to an enhancement of both organic and inorganic secondary aerosols in the atmosphere, as well as an increase in aerosol average diameter. Considering the bulk composition alone, CCN concentrations were substantially overpredicted (29.6 ± 45.1% at 0.2% supersaturation and 57.3 ± 30.0% at 1.0% supersaturation). Overall, the impact of composition on the calculated NCCN decreases with decreasing supersaturation, partially because using bulk composition introduces less bias for large diameters and lower critical supersaturations. Results suggest that the consideration of only inorganic fraction improves the calculated NCCN. Introducing a size-dependent chemical composition based on filter measurements from previous campaigns has considerably improved simulated values for NCCN (average overprediction error 3.0 ± 33.4% at 0.20% supersaturation and average under prediction error 2.4 ± 20.5% at 1.0% supersaturation). This study provides the first insight on aerosol real-time composition and hygroscopicity on a~site strongly impacted by emissions of a unique vehicular fleet due to the extensive biofuel usage.

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Evaluation of Second-Hand Exposure to Electronic Cigarette Vaping under a Real Scenario: Measurements of Ultrafine Particle Number Concentration and Size Distribution and Comparison with Traditional Tobacco Smoke

Toxics ◽

10.3390/toxics7040059 ◽

2019 ◽

Vol 7 (4) ◽

pp. 59 ◽

Cited By ~ 1

Author(s):

Jolanda Palmisani ◽

Alessia Di Gilio ◽

Laura Palmieri ◽

Carmelo Abenavoli ◽

Marco Famele ◽

...

Keyword(s):

Size Distribution ◽

Tobacco Smoke ◽

Ultrafine Particles ◽

Natural Ventilation ◽

Ultrafine Particle ◽

Inhalation Exposure ◽

Number Concentration ◽

Aerosol Size Distribution ◽

High Temporal Resolution ◽

The Impact

The present study aims to evaluate the impact of e-cig second-hand aerosol on indoor air quality in terms of ultrafine particles (UFPs) and potential inhalation exposure levels of passive bystanders. E-cig second-hand aerosol characteristics in terms of UFPs number concentration and size distribution exhaled by two volunteers vaping 15 different e-liquids inside a 49 m3 room and comparison with tobacco smoke are discussed. High temporal resolution measurements were performed under natural ventilation conditions to simulate a realistic exposure scenario. Results showed a systematic increase in UFPs number concentration (part cm−3) related to a 20-min vaping session (from 6.56 × 103 to 4.01 × 104 part cm−3), although this was one up to two order of magnitude lower than that produced by one tobacco cigarette consumption (from 1.12 × 105 to 1.46 × 105 part cm−3). E-cig second-hand aerosol size distribution exhibits a bimodal behavior with modes at 10.8 and 29.4 nm in contrast with the unimodal typical size distribution of tobacco smoke with peak mode at 100 nm. In the size range 6–26 nm, particles concentration in e-cig second-hand aerosol were from 2- (Dp = 25.5 nm) to 3800-fold (Dp = 9.31 nm) higher than in tobacco smoke highlighting that particles exhaled by users and potentially inhaled by bystanders are nano-sized with high penetration capacity into human airways.

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Quantifying the aerosol effect on droplet size distribution at cloud top

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-7839-2019 ◽

2019 ◽

Vol 19 (11) ◽

pp. 7839-7857

Author(s):

Lianet Hernández Pardo ◽

Luiz Augusto Toledo Machado ◽

Micael Amore Cecchini ◽

Madeleine Sánchez Gácita

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Initial Conditions ◽

Cloud Condensation Nuclei ◽

Droplet Size Distribution ◽

Number Concentration ◽

Population Characteristics ◽

Aerosol Size Distribution ◽

Effective Diameter ◽

Distribution Sensitivity

Abstract. This work uses the number concentration-effective diameter phase-space to test cloud sensitivity to variations in the aerosol population characteristics, such as the aerosol size distribution, number concentration and hygroscopicity. It is based on the information from the top of a cloud simulated by a bin-microphysics single-column model, for initial conditions typical of the Amazon, using different assumptions regarding the entrainment and the aerosol size distribution. It is shown that the cloud-top evolution can be very sensitive to aerosol properties, but the relative importance of each parameter is variable. The sensitivity to each aerosol characteristic varies as a function of the parameter tested and is conditioned by the base values of the other parameters, showing a specific dependence for each configuration of the model. When both the entrainment and the bin treatment of the aerosol are allowed, the largest influence on the droplet size distribution sensitivity was obtained for the median radius of the aerosols and not for the total number concentration of aerosols. Our results reinforce that the cloud condensation nuclei activity can not be predicted solely on the basis of the w∕Na supersaturation-based regimes.

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Optical Properties of the Urban Aerosol Particles Obtained from Ground Based Measurements and Satellite-Based Modelling Studies

Advances in Meteorology ◽

10.1155/2015/898376 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Genrik Mordas ◽

Nina Prokopciuk ◽

Steigvilė Byčenkienė ◽

Jelena Andriejauskienė ◽

Vidmantas Ulevicius

Keyword(s):

Optical Properties ◽

Light Scattering ◽

Urban Environment ◽

Size Distribution ◽

Number Concentration ◽

Scattering Coefficient ◽

Dust Particles ◽

Aerosol Size Distribution ◽

Air Masses ◽

The Impact

Applications of satellite remote sensing data combined with ground measurements and model simulation were applied to study aerosol optical properties as well as aerosol long-range transport under the impact of large scale circulation in the urban environment in Lithuania (Vilnius). Measurements included the light scattering coefficients at 3 wavelengths (450, 550, and 700 nm) measured with an integrating nephelometer and aerosol particle size distribution (0.5–12 μm) and number concentration (Dpa> 0.5 μm) registered by aerodynamic particle sizer. Particle number concentration and mean light scattering coefficient varied from relatively low values of 6.0 cm−3and 12.8 Mm−1associated with air masses passed over Atlantic Ocean to relatively high value of 119 cm−3and 276 Mm−1associated with South-Western air masses. Analysis shows such increase in the aerosol light scattering coefficient (276 Mm−1) during the 3rd of July 2012 was attributed to a major Sahara dust storm. Aerosol size distribution with pronounced coarse particles dominance was attributed to the presence of dust particles, while resuspended dust within the urban environment was not observed.

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On aerosol hygroscopicity, cloud condensation nuclei (CCN) spectra and critical supersaturation measured at two remote islands of Korea between 2006 and 2009

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-19683-2011 ◽

2011 ◽

Vol 11 (7) ◽

pp. 19683-19727 ◽

Cited By ~ 2

Author(s):

J. H. Kim ◽

S. S. Yum ◽

S. Shim ◽

S.-C. Yoon ◽

J. G. Hudson ◽

...

Keyword(s):

Size Distribution ◽

Total Concentration ◽

Cloud Condensation Nuclei ◽

Geometric Mean ◽

Aerosol Size Distribution ◽

Monitoring Site ◽

Hygroscopic Growth ◽

Condensation Nuclei ◽

Critical Supersaturation ◽

Aerosol Hygroscopicity

Abstract. Aerosol size distribution, total concentration (i.e., condensation nuclei (CN) concentration, NCN), cloud condensation nuclei (CCN) concentration (NCCN), hygroscopicity at ~90 % relative humidity (RH) were measured at a background monitoring site at Gosan, Jeju Island, south of the Korea Peninsula in August 2006, April to May 2007 and August to October 2008. Similar measurement took place in August 2009 at another background site (Baengnyeongdo Comprehensive Monitoring Observatory, BCMO) on the island of Baengnyeongdo, off the west coast of the Korean Peninsula. Both islands were found to be influenced by continental sources regardless of season and year. Average values for all of the measured NCCN at 0.2, 0.6 and 1.0 % supersaturations (S), NCN, and geometric mean diameter (Dg) from both islands were in the range of 1043–3051 cm−3, 2076–4360 cm−3, 2713–4694 cm−3, 3890–5117 cm−3 and 81–98 nm, respectively. Although the differences in Dg and NCN were small between Gosan and BCMO, NCCN at various S was much higher at the latter, which is closer to China. Most of the aerosols were internally mixed and no notable differences in hygroscopicity were found between the days of strong pollution influence and the non-pollution days for both islands. During the 2008 and 2009 campaigns, critical supersaturation for cloud nucleation (Sc) for selected particle sizes was measured. Particles of 100 nm diameters had mean Sc of 0.19 ± 0.02 % during 2008 and those of 81 and 110 nm diameters had mean Sc of 0.26 ± 0.07 % and 0.17 ± 0.04 %, respectively, during 2009. Hygroscopicity parameters estimated from the measured Sc were mostly higher than the ones from the measured hygroscopic growth at ~90 % RH. For the 2008 campaign, NCCN at 0.2, 0.6 and 1.0 % S were predicted based on the measured dry particle size distribution and various ways of representing aerosol hygroscopicity. The best closure was obtained when temporally varying and size-resolved hygroscopicity information from HTDMA was used, for which the average relative deviations from the measured values were 19 % for 1.0 % S and 28 % for 0.2 % S. Prescribing a constant hygroscopicity parameter suggested in literature (κ = 0.3) for all sizes and time resulted in the average relative deviations, 25–40 %. When constant hygroscopicity was assumed, the relative deviation tended to increase with decreasing NCCN, which was accompanied by increase of sub-100 nm fraction. These results suggest that hygroscopicity information for aerosols of diameters smaller than 100 nm is crucial for more accurate prediction of NCCN.

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Long-term observations of cloud condensation nuclei in the Amazon rain forest – Part 1: Aerosol size distribution, hygroscopicity, and new model parametrizations for CCN prediction

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-15709-2016 ◽

2016 ◽

Vol 16 (24) ◽

pp. 15709-15740 ◽

Cited By ~ 45

Author(s):

Mira L. Pöhlker ◽

Christopher Pöhlker ◽

Florian Ditas ◽

Thomas Klimach ◽

Isabella Hrabe de Angelis ◽

...

Keyword(s):

Size Distribution ◽

Aerosol Particle ◽

Rain Forest ◽

Seasonal Cycle ◽

Cloud Condensation Nuclei ◽

Number Concentration ◽

Aerosol Size Distribution ◽

Condensation Nuclei ◽

Central Amazon

Abstract. Size-resolved long-term measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a 1-year period and full seasonal cycle (March 2014–February 2015). The measurements provide a climatology of CCN properties characteristic of a remote central Amazonian rain forest site.The CCN measurements were continuously cycled through 10 levels of supersaturation (S  =  0.11 to 1.10 %) and span the aerosol particle size range from 20 to 245 nm. The mean critical diameters of CCN activation range from 43 nm at S  =  1.10 % to 172 nm at S  =  0.11 %. The particle hygroscopicity exhibits a pronounced size dependence with lower values for the Aitken mode (κAit  =  0.14 ± 0.03), higher values for the accumulation mode (κAcc  =  0.22 ± 0.05), and an overall mean value of κmean  =  0.17 ± 0.06, consistent with high fractions of organic aerosol.The hygroscopicity parameter, κ, exhibits remarkably little temporal variability: no pronounced diurnal cycles, only weak seasonal trends, and few short-term variations during long-range transport events. In contrast, the CCN number concentrations exhibit a pronounced seasonal cycle, tracking the pollution-related seasonality in total aerosol concentration. We find that the variability in the CCN concentrations in the central Amazon is mostly driven by aerosol particle number concentration and size distribution, while variations in aerosol hygroscopicity and chemical composition matter only during a few episodes.For modeling purposes, we compare different approaches of predicting CCN number concentration and present a novel parametrization, which allows accurate CCN predictions based on a small set of input data.

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