Aerosol hygroscopicity and CCN activation kinetics in a boreal forest environment during the 2007 EUCAARI campaign

Cerully, K. M.; Raatikainen, Tomi; Lance, Sara; Tkacik, Daniel S.; Tiitta, Petri; Petäj̈ä, Tuukka; Ehn, Mikael; Kulmala, Markku; Worsnop, Douglas R.; Laaksonen, A.; Smith, James N.; Nenes, Athanasios

doi:10.5194/acp-11-12369-2011

Cited by 118 publications

(143 citation statements)

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“…A peak in aerosol hygroscopicity is observed around midday when D c reaches its minimum. Several previous studies have reported such behaviour in Hyytiälä and have attributed it to the vegetation activity, photochemistry and the ageing of organics during sunlight hours (Sihto et al, 2011;Cerully et al, 2011;Paramonov et al, 2013). While no diurnal pattern of aerosol hygroscopicity is visible for Jungfraujoch for winter and spring, a very clear pattern does exist in the summer and autumn.…”

Section: Ccn and Their Hygroscopicitymentioning

confidence: 83%

A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network

et al. 2015

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Published by Copernicus Publications on behalf of the European Geosciences Union. M. Paramonov et al.: A synthesis of CCNC measurements within the EUCAARI networkAbstract. Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (N CCN ) to the total number concentration of particles (N CN ), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations -exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A 50 and A 100 , respectively) renders a much more stable dependence of A on S; A 50 and A 100 also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter κ decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations κ increased with size. In fact, in Hyytiälä, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5 % significance level. In a boreal environment the assumption of a size-independent κ can lead to a potentially substantial overestimation of N CCN at S levels above 0.6 %. The same is true for other locations where κ was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of N CCN , total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol-cloud interactions in various environments.

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Section: Ccn and Their Hygroscopicitymentioning

confidence: 83%

A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network

et al. 2015

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“…Heterogeneity in the chemical composition and particle size both contribute to broadening of p(s c ) (Lance, 2007;Svenningsson and Bilde, 2008;Rose et al, 2008;Cerully et al, 2011) and affects the slope parameter, C, of the activation spectrum.…”

Section: Ccn Measurements and Derivation Of κ Ccncmentioning

confidence: 99%

“…To obtain size-resolved CCN activation spectra, a similar experimental setup to Cerully et al (2011) was used. The sampled aerosol was electrostatically classified with a differential mobility analyzer (nanoDMA, TSI 3085) (Chen et al, 1998) using a 210-Po neutralizer.…”

Section: Measurements and Instrumentationmentioning

confidence: 99%

Aerosol mixing state, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

et al. 2013

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Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. κ-Köhler theory is used to evaluate the characteristic hygroscopicity parameter, κ*, for the CCN active aerosol population using both size-resolved HTMDA and size-resolved CCNc measurements. Organic mass fractions (f_org) are evaluated from size-resolved aerosol mass spectrometer (AMS) measurements, from which predictions of the hygroscopicity parameter are compared against κ*.

Strong diurnal changes in aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF) events are correlated with an increased κ* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN at 0.51% ± 0.06% supersaturation can surpass by more than a factor of two the corresponding concentrations of 100 nm particles. We also find that at 06:00–08:00 LT throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally mixed fraction for 40 nm particles and 30% externally mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as "internally mixed".

Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events), the early morning "rush hour" and the entire campaign. We show that κ* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for κ* versus particle size, which can be attributed to unresolved mixing state and the presence of refractory material not measured by the AMS. Measured κ* typically ranges from 0.2 to 0.35, and organics typically make up 60–85 % of the aerosol mass in the size range studied. We show that κ_AMS is able to describe CCN concentrations reasonably well, provided mixing-state information is available, especially at the highest CCN concentrations. This is consistent with other CCN studies carried out in urban environments, and is partly due to the fact that the highest CCN concentrations occur during the daytime when the aerosol is internally mixed. During the early morning rush hour, however, failing to account for the aerosol mixing state results in systematic overestimation of CCN concentrations by as much as 50–100% on average

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“…To account for hygroscopicity and dry size differences between aerosol, both droplet sizes are selected from the point where activation is first observed. TDGA has been applied to several ambient aerosol samples (AsaAwuku et al, 2011;Bougiatioti et al, 2009Bougiatioti et al, , 2011Lance et al, 2009;Murphy et al, 2009;Padró et al, 2010Padró et al, , 2011Cerully et al, 2011), secondary organic aerosol (SOA) (Engelhart et al, 2008(Engelhart et al, , 2011Asa-Awuku et al, 2009 and laboratory-generated aerosol (Moore et al, 2008;Kumar et al, 2011a,b). In general, slower kinetics than calibration aerosol have been related to insoluble organics from SOA chamber experiments (Asa-Awuku et al, 2009), fresh exhaust plumes , and mineral dust particles when using a dry generation technique (Kumar et al, 2011a,b).…”

Section: T Raatikainen Et Al: Activation Kinetics From Measurementsmentioning

confidence: 99%

A coupled observation – modeling approach for studying activation kinetics from measurements of CCN activity

et al. 2012

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Abstract. This paper presents an approach to study droplet activation kinetics from measurements of CCN activity by the Continuous Flow Streamwise Thermal Gradient CCN Chamber (CFSTGC) and a comprehensive model of the instrument and droplet growth. The model, which can be downloaded from http://nenes.eas.gatech.edu/Experiments/ CFSTGC.html, is evaluated against a series of experiments with ammonium sulfate calibration aerosol. Observed and modeled droplet sizes are in excellent agreement for a water vapor uptake coefficient ∼0.2, which is consistent with theoretical expectations. The model calculations can be considerably accelerated without significant loss of accuracy by assuming simplified instrument geometry and constant parabolic flow velocity profiles. With these assumptions, the model can be applied to large experimental data sets to infer kinetic growth parameters while fully accounting for water vapor depletion effects and changes in instrument operation parameters such as the column temperature, flow rates, sheath and sample flow relative humidities, and pressure. When the effects of instrument operation parameters, water vapor depletion and equilibrium dry particle properties on droplet size are accounted for, the remaining variations in droplet size are most likely due to non-equilibrium processes such as those caused by organic surface films, slow solute dissociation and glassy or highly viscous particle states. As an example of model application, data collected during a research flight in the ARCTAS 2008 campaign are analyzed. The model shows that water vapor depletion effects can explain changes in the observed average droplet size.

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Aerosol hygroscopicity and CCN activation kinetics in a boreal forest environment during the 2007 EUCAARI campaign

Cited by 118 publications

References 89 publications

A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network

A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network

Aerosol mixing state, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

A coupled observation – modeling approach for studying activation kinetics from measurements of CCN activity

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