Laboratory Studies and Numerical Simulations of Cloud Droplet Formation under Realistic Supersaturation Conditions

Stratmann, Frank; Kiselev, Alexei; Wurzler, S.; Wendisch, Manfred; Heintzenberg, Jost; Charlson, Robert J.; Diehl, K.; Wex, Heike; Schmidt, S.

doi:10.1175/1520-0426(2004)021<0876:lsanso>2.0.co;2

Cited by 92 publications

(111 citation statements)

References 28 publications

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“…LACIS (Leipzig Aerosol Cloud Interaction Simulator, Stratmann et al, 2004) is a multi-purpose instrument for investigating aerosol cloud interactions and cloud microphysical processes such as aerosol particle hygroscopic growth, cloud droplet activation, growth and freezing. In the framework of the present paper, it is used for investigating the immersion freezing behaviour of well-characterised, size-selected particles generated from a Snomax TM solution/suspension as a function of temperature with only one particle immersed in each droplet.…”

Section: Lacismentioning

confidence: 99%

Immersion freezing of ice nucleation active protein complexes

et al. 2013

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Utilising the Leipzig Aerosol Cloud Interaction Simulator (LACIS), the immersion freezing behaviour of droplet ensembles containing monodisperse particles, generated from a Snomax™ solution/suspension, was investigated. Thereto ice fractions were measured in the temperature range between −5 °C to −38 °C. Snomax™ is an industrial product applied for artificial snow production and contains Pseudomonas syringae} bacteria which have long been used as model organism for atmospheric relevant ice nucleation active (INA) bacteria. The ice nucleation activity of such bacteria is controlled by INA protein complexes in their outer membrane.

In our experiments, ice fractions increased steeply in the temperature range from about −6 °C to about −10 °C and then levelled off at ice fractions smaller than one. The plateau implies that not all examined droplets contained an INA protein complex. Assuming the INA protein complexes to be Poisson distributed over the investigated droplet populations, we developed the CHESS model (stoCHastic modEl of similar and poiSSon distributed ice nuclei) which allows for the calculation of ice fractions as function of temperature and time for a given nucleation rate. Matching calculated and measured ice fractions, we determined and parameterised the nucleation rate of INA protein complexes exhibiting class III ice nucleation behaviour. Utilising the CHESS model, together with the determined nucleation rate, we compared predictions from the model to experimental data from the literature and found good agreement.

We found that (a) the heterogeneous ice nucleation rate expression quantifying the ice nucleation behaviour of the INA protein complex is capable of describing the ice nucleation behaviour observed in various experiments for both, Snomax™ and P. syringae bacteria, (b) the ice nucleation rate, and its temperature dependence, seem to be very similar regardless of whether the INA protein complexes inducing ice nucleation are attached to the outer membrane of intact bacteria or membrane fragments, (c) the temperature range in which heterogeneous droplet freezing occurs, and the fraction of droplets being able to freeze, both depend on the actual number of INA protein complexes present in the droplet ensemble, and (d) possible artifacts suspected to occur in connection with the drop freezing method, i.e., the method frequently used by biologist for quantifying ice nucleation behaviour, are of minor importance, at least for substances such as P. syringae, which induce freezing at comparably high temperatures. The last statement implies that for single ice nucleation entities such as INA protein complexes, it is the number of entities present in the droplet population, and the entities' nucleation rate, which control the freezing behaviour of the droplet population. Quantities such as ice active surface site density are not suitable in this context.

The results obtained in this study allow a different perspective on the quantification of the immersi...

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Section: Lacismentioning

confidence: 99%

Immersion freezing of ice nucleation active protein complexes

et al. 2013

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“…The agreement of the thus derived RH with the hygroscopic growth of known salts was shown in Wex et al (2005). For the second mode LACIS can be operated at a slight water vapor super-saturation (Stratmann et al, 2004). For this, the dew point temperatures have to be larger than the wall temperature of LACIS.…”

Section: Methodsmentioning

confidence: 54%

“…It has been described in detail before (Stratmann et al, 2004;Wex et al, 2005). A draft of the setup is shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…the equilibrium diameter, of atmospheric aerosol particles at atmospheric relative humidities has been an object of many studies (e.g., Svenningsson et al, 1992Svenningsson et al, , 1997Zhang et al, 1993;Pitchford and McMurry, 1994;Swietlicki et al, 1999;Busch et al, 2002;Massling et al, 2003); because the hygroscopically grown size of the particles in the atmosphere determines their influence on incoming solar radiation. LACIS, the Leipzig Aerosol Cloud Interaction Simulator, has been build to examine both, hygroscopic growth and particle activation to cloud droplets (Stratmann et al, 2004). It has been shown, that measurements of the hygroscopic growth are possible with LACIS at RHs up to 99.1% .…”

Section: Introductionmentioning

confidence: 99%

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Calibration of LACIS as a CCN detector and its use in measuring activation and hygroscopic growth of atmospheric aerosol particles

et al. 2006

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Abstract. A calibration for LACIS (Leipzig Aerosol CloudInteraction Simulator) for its use as a CCN (cloud condensation nuclei) detector has been developed. For this purpose, sodium chloride and ammonium sulfate particles of known sizes were generated and their grown sizes were detected at the LACIS outlet. From these signals, the effective critical super-saturation was derived as a function of the LACIS wall temperature. With this, LACIS is calibrated for its use as a CCN detector. The applicability of LACIS for measurements of the droplet activation, and also of the hygroscopic growth of atmospheric aerosol particles was tested. The activation of the urban aerosol particles used in the measurements was found to occur at a critical super-saturation of 0.46% for particles with a dry diameter of 75 nm, and at 0.42% for 85 nm, respectively. Hygroscopic growth was measured for atmospheric aerosol particles with dry diameters of 150, 300 and 350 nm at relative humidities of 98 and 99%, and it was found that the larger dry particles contained a larger soluble volume fraction of about 0.85, compared to about 0.6 for the 150 nm particles.

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“…Among the important problems in obtaining a detailed understanding of the formation of cloud droplets from aerosols are the uncertainties in the condensation and evaporation rates of water vapor on existing droplets under supersaturation conditions (Chuang 2002). The condensation rate of water vapor on pure water droplets has been measured in the laboratory by using an expansion chamber (Winkler et al 2006) and a laminar flow tube (Stratmann et al 2004). In the expansion chamber methods, the condensation rate is determined directly from the measured time-dependent droplet size under known supersaturation conditions.…”

Section: Introductionmentioning

confidence: 99%

Corona-Imaging Colorimetric Method for Accurate Measurement of the Size of Water Droplets in an Expansion Chamber

Aoki

Moteki

Kondo

2013

Aerosol Science and Technology

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Accurate and time-resolved measurement of the size of water droplets is a prerequisite for the study of the microphysical processes of cloud formation by using an expansion chamber. We developed a droplet sizing method that uses color images of coronae observed under illumination of a white-light beam, also known as the corona-imaging colorimetry (CIC) method. In the CIC method, RGB data from images obtained by a commercial digital camera are converted into standard colorimetric parameters. The droplet size is estimated by optimizing the agreement of the measured colorimetric parameters with those estimated from Mie theory. For polystyrene latex spheres suspended in water, the particles size estimated by the CIC method agrees to within 2% of the predetermined value. We apply this method to the time-resolved measurement of the size of water droplets formed in an expansion chamber. The CIC method is technically simple and enables accurate and instantaneous measurements of the size of droplets with diameters larger than about 10 μm, which is the typical size of cloud droplets that form in the atmosphere.

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Laboratory Studies and Numerical Simulations of Cloud Droplet Formation under Realistic Supersaturation Conditions

Cited by 92 publications

References 28 publications

Immersion freezing of ice nucleation active protein complexes

Immersion freezing of ice nucleation active protein complexes

Calibration of LACIS as a CCN detector and its use in measuring activation and hygroscopic growth of atmospheric aerosol particles

Corona-Imaging Colorimetric Method for Accurate Measurement of the Size of Water Droplets in an Expansion Chamber

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