Evaporation kinetics of ventilated waterdrops coated with octadecanol monolayers

Seaver, Mark; Peele, John R.; Manuccia, T. J.; Rubel, Glenn O.; Ritchie, G.

doi:10.1021/j100194a053

Cited by 19 publications

(12 citation statements)

References 6 publications

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“…It is also well established from laboratory experiments that the presence of an organic film on a flat liquid surface is able to limit ␣ across the liquid-gas interface. Laboratory studies on synthetic aerosol composed of organic films do suggest that ␣ on the order of 10 Ϫ4 to 10 Ϫ5 are possible (Otani and Wang 1984;Rubel and Gentry 1984;Seaver et al 1992). As noted in McFiggans et al (2006), surfactant films on ambient aerosol are more likely to be expanded and porous, rather than con- …”

Section: ϫ3mentioning

confidence: 99%

Cloud Activating Properties of Aerosol Observed during CELTIC

Stroud

Nenes

Jimenez³

et al. 2007

Journal of the Atmospheric Sciences

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Measurements of aerosol size distribution, chemical composition, and cloud condensation nuclei (CCN) concentration were performed during the Chemical Emission, Loss, Transformation, and Interactions with Canopies (CELTIC) field program at Duke Forest in North Carolina. A kinetic model of the cloud activation of ambient aerosol in the chamber of the CCN instrument was used to perform an aerosol-CCN closure study. This study advances prior investigations by employing a novel fitting algorithm that was used to integrate scanning mobility particle sizer (SMPS) measurements of aerosol number size distribution and aerosol mass spectrometer (AMS) measurements of the mass size distribution for sulfate, nitrate, ammonium, and organics into a single, coherent description of the ambient aerosol in the size range critical to aerosol activation (around 100-nm diameter). Three lognormal aerosol size modes, each with a unique internally mixed composition, were used as input into the kinetic model. For the two smaller size modes, which control CCN number concentration, organic aerosol mass fractions for the defined cases were between 58% and 77%. This study is also unique in that the water vapor accommodation coefficient was estimated based on comparing the initial timing for CCN activation in the instrument chamber with the activation predicted by the kinetic model. The kinetic model overestimated measured CCN concentrations, especially under polluted conditions. Prior studies have attributed a positive model bias to an incomplete understanding of the aerosol composition, especially the role of organics in the activation process. This study shows that including measured organic mass fractions with an assumed organic aerosol speciation profile (pinic acid, fulvic acid, and levoglucosan) and an assumed organic aerosol solubility of 0.02 kg kg Ϫ1 still resulted in a significant model positive bias for polluted case study periods. The slope and y intercept for the CCN predicted versus CCN observed regression was found to be 1.9 and Ϫ180 cm Ϫ3 , respectively. The overprediction generally does not exceed uncertainty limits but is indicative that a bias exists in the measurements or application of model. From this study, uncertainties in the particle number and mass size distributions as the cause for the model bias can be ruled out. The authors are also confident that the model is including the effects of growth kinetics on predicted activated number. However, one cannot rule out uncertainties associated with poorly characterized CCN measurement biases, uncertainties in assumed organic solubility, and uncertainties in aerosol mixing state. Sensitivity simulations suggest that assuming either an insoluble organic fraction or external aerosol mixing were both sufficient to reconcile the model bias.

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Section: ϫ3mentioning

confidence: 99%

Cloud Activating Properties of Aerosol Observed during CELTIC

Stroud

Nenes

Jimenez³

et al. 2007

Journal of the Atmospheric Sciences

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“…Here, we see that depending on droplet size, the sensitivity asymptotes at a value of 1 given sufficiently small α c , with values on the order of 10 −1 to 10 −3 depending on droplet size. In contrast with α T , however, laboratory measurements of α c show that these values can be as low as ∼10 −5 in the presence of organic films on the surface of the droplets [ Rubel and Gentry , 1984; Seaver et al , 1992], and evidence that such particles may exist in the atmosphere has been presented [ Chuang , 2003]. See Barnes [1986] and Chuang [2003] for more comprehensive reviews of this subject.…”

Section: Sensitivity Of the Condensational Growth Ratementioning

confidence: 99%

Sensitivity of cloud condensation nuclei activation processes to kinetic parameters

Chuang

2006

J. Geophys. Res.

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[1] The activation of cloud condensation nuclei to form cloud drops can be a kinetically limited process under some circumstances. Here the sensitivity of particle activation to parameters that are related to kinetic processes, in particular condensational growth and ambient supersaturation, is examined. Specifically, the parameters studied are the thermal and mass accommodation coefficients, the rate of solute dissolution for a particle, and the updraft velocity. Results are based on the equation for condensational growth and simulations using adiabatic parcel models. We conclude that activation is not very sensitive to the thermal accommodation coefficient but is sensitive to the mass accommodation coefficient below some critical value of $0.1 to 0.001. Dissolution rates (defined for 100 nm dry particles) in the range of 10 min to 1 day can significantly affect activation. Sensitivity to updraft velocity uncertainties can be significant and are likely to be more important for polluted rather than clean conditions.

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“…Laboratory experiments have shown that compressed surface films of certain organic compounds can retard evaporation and/or condensation of water from flat surfaces (e.g., Barnes 1986;McNamee et al 1998) and droplets (Snead and Zung 1968;Garrett 1971;Rubel and Gentry 1984;Otani and Wang 1984;Seaver et al 1992;Xiong et al 1998), although the mechanism for such retardation remains unconfirmed. The magnitude of the effect also varies depending on the technique and compounds used.…”

Section: Evidence For Film-forming Compoundsmentioning

confidence: 99%

Analysis of the Influence of Film-Forming Compounds on Droplet Growth: Implications for Cloud Microphysical Processes and Climate

Feingold¹,

2002

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Decades of cloud microphysical research have not provided conclusive understanding of the physical processes responsible for droplet spectral broadening. Numerous mechanisms have been proposed-for example, entrainment mixing, vortex shedding, giant cloud condensation nuclei (CCN), chemical processing of CCN, and radiative cooling-all of which are likely candidates under select conditions. In this paper it is suggested that variability in the composition of CCN, and in particular, the existence of condensation inhibiting compounds, is another possible candidate. The inferred potential abundance of these amphiphilic film-forming compounds (FFCs) suggests that their effect may be important. Using a cloud parcel model with a simplified treatment of the effect of FFCs, it is shown that modest concentrations of FFCs (on the order of 5% of the total aerosol mass) can have a marked effect on drop growth and can cause significant increases in spectral dispersions. Moreover, it is shown that FFCs may, in some cases, reduce the number concentration of cloud droplets, with implications for cloud-climate feedbacks. This trend is at least in qualitative agreement with results from a recent field campaign.

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Evaporation kinetics of ventilated waterdrops coated with octadecanol monolayers

Cited by 19 publications

References 6 publications

Cloud Activating Properties of Aerosol Observed during CELTIC

Cloud Activating Properties of Aerosol Observed during CELTIC

Sensitivity of cloud condensation nuclei activation processes to kinetic parameters

Analysis of the Influence of Film-Forming Compounds on Droplet Growth: Implications for Cloud Microphysical Processes and Climate

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