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Sonia M. Kreidenweis - One of the best experts on this subject based on the ideXlab platform.
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A single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity – Part 3: Including surfactant partitioning
Atmospheric Chemistry and Physics, 2013Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:Abstract. Atmospheric particles can serve as cloud Condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Kohler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud Condensation Nucleus activity. The presented formulation incorporates analytical approximations of surfactant partitioning to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code.
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a single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity part 3 including surfactant partitioning
Atmospheric Chemistry and Physics, 2012Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:Abstract. Atmospheric particles can serve as cloud Condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Kohler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud Condensation Nucleus activity. The presented formulation incorporates analytical approximations of surfactant partitioning to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code.
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A single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity – Part 3: Including surfactant partitioning
Atmospheric Chemistry and Physics Discussions, 2012Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:Abstract. Atmospheric particles can serve as cloud Condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Köhler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud Condensation Nucleus activity. The presented formulation incorporates the analytical approximations introduced by Raatikainen and Laaksonen to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code. We apply this extended model to discuss several uncertainties that hinder our ability to precisely pinpoint the role of surface tension in cloud droplet activation with current measurement and data analysis approaches.
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A single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity – Part 2: Including solubility
Atmospheric Chemistry and Physics, 2008Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:The ability of a particle to serve as a cloud Condensation Nucleus in the atmosphere is determined by its size, hygroscopicity and its solubility in water. Usually size and hygroscopicity alone are sufficient to predict CCN activity. Single parameter representations for hygroscopicity have been shown to successfully model complex, multicomponent particles types. Under the assumption of either complete solubility, or complete insolubility of a component, it is not necessary to explicitly include that component's solubility into the single parameter framework. This is not the case if sparingly soluble materials are present. In this work we explicitly account for solubility by modifying the single parameter equations. We demonstrate that sensitivity to the actual value of solubility emerges only in the regime of 2×10 −1 –5×10 −4 , where the solubility values are expressed as volume of solute per unit volume of water present in a saturated solution. Compounds that do not fall inside this sparingly soluble envelope can be adequately modeled assuming they are either infinitely soluble in water or completely insoluble.
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a single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity part 2 including solubility
Atmospheric Chemistry and Physics, 2008Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:The ability of a particle to serve as a cloud Condensation Nucleus in the atmosphere is determined by its size, hygroscopicity and its solubility in water. Usually size and hygroscopicity alone are sufficient to predict CCN activity. Single parameter representations for hygroscopicity have been shown to successfully model complex, multicomponent particles types. Under the assumption of either complete solubility, or complete insolubility of a component, it is not necessary to explicitly include that component's solubility into the single parameter framework. This is not the case if sparingly soluble materials are present. In this work we explicitly account for solubility by modifying the single parameter equations. We demonstrate that sensitivity to the actual value of solubility emerges only in the regime of 2×10 −1 –5×10 −4 , where the solubility values are expressed as volume of solute per unit volume of water present in a saturated solution. Compounds that do not fall inside this sparingly soluble envelope can be adequately modeled assuming they are either infinitely soluble in water or completely insoluble.
Peter H. Mcmurry - One of the best experts on this subject based on the ideXlab platform.
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Sizing Small Sulfuric Acid Particles with an Ultrafine Particle Condensation Nucleus Counter
Aerosol Science and Technology, 2002Co-Authors: David R. Hanson, Fred L. Eisele, S. M. Ball, Peter H. McmurryAbstract:The sizing capability of an ultrafine particle Condensation Nucleus counter (which uses butanol as the condensing fluid) equipped with pulse height analysis was evaluated in terms of particle composition for sulfuric acid aerosol and sulfuric acid aerosol to which gas-phase ammonia had been added. The response of the counter depended on composition for a range of particle sizes when the water partial pressure was low. For water partial pressures 4 nm in diameter, the response (pulse heights) of the instrument to particles of a given size was substantially different for sulfuric acid particles and those that were neutralized with ammonia. For water partial pressures > 5 Torr, however, neutralizing the particles with ammonia had little effect on pulse height distributions. For particles smaller than 4 nm diameter the pulse heights were insensitive to exposure to ammonia.
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The History of Condensation Nucleus Counters
Aerosol Science and Technology, 2000Co-Authors: Peter H. McmurryAbstract:Condensation of supersaturated vapors has been used for more than a century to grow small aerosol particles to sizes that can be detected optically. This paper discusses the history of instruments that use Condensation to detect particles. I divide this history into two main sections. The first of these focuses on the development of expansion-type instruments including the ''dust counters'' in which John Aitken played the decisive role and ''photoelectric Nucleus counters'' primarily by L. W. Pollak and coworkers. The second section deals with the development of steady-flow Condensation Nucleus counters (CNCs) in which Jean Bricard and coworkers played the decisive role. The importance of calibration methodologies is also pointed out. Refinements by instrumentation manufacturers and many aerosol scientists have led to the reliable, accurate instruments that are widely used today.
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Inversion of ultrafine Condensation Nucleus counter pulse height distributions to obtain nanoparticle (∼3–10 nm) size distributions
Journal of Aerosol Science, 1998Co-Authors: Rodney J. Weber, Mark R. Stolzenburg, Spyros N. Pandis, Peter H. McmurryAbstract:Abstract Previous work ( Ahn and Liu (1990) J. Aerosol. Sci. 21, 249–261; Brockmann (1981) Ph.D. Thesis, University of Minnesota; Rebours et al. (1992) J. Aerosol. Sci. 23, S189–S192; Stolzenburg (1988) Ph.D. thesis, University of Minnesota) has shown that for particles smaller than about 15 nm, pulse heights produced by the optical detector in a white-light ultrafine Condensation Nucleus counter (UCNC; Stolzenburg and McMurry (1991) Aerosol. Sci. Technol. 14, 48–65) decrease with initial particle size. We have previously reported on the use of pulse heights from this instrument to determine the concentrations of freshly nucleated atmospheric nanoparticles in the 3–4 nm diameter range ( Weber et al. (1995) J. Atm. Sci. 52, 2242–2257; Weber et al. (1997) J. Geophys. Res. 102, 4375–4385). In this paper we report on the inversion of measured pulse-height distributions to obtain size distributions of particles in the 3–10 nm diameter range. Using methods developed by Stolzenburg ( Stolzenburg (1988) Ph.D. Thesis, University of Minnesota) the effect of diffusional broadening is taken into account so as to obtain monodisperse kernel functions from measured pulse-height distributions produced by DMA-generated calibration aerosols in the 3–50 nm diameter range. These kernel functions are then used with the MICRON algorithm described by Wolfenbarger and Seinfeld (1990, J. Aerosol. Sci. 21, 227–247) to obtain size distributions of nanoparticle aerosols from measured pulse height distributions. Calculations were done to ensure that assumed pulse-height data generated from selected known size distributions can be inverted to recover the original size distribution. Results from these validation studies are discussed. Applications of the inversion algorithm to data acquired in studies of homogeneous nucleation in the atmosphere are also presented.
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inversion of ultrafine Condensation Nucleus counter pulse height distributions to obtain nanoparticle 3 10 nm size distributions
Journal of Aerosol Science, 1998Co-Authors: Rodney J. Weber, Mark R. Stolzenburg, Spyros N. Pandis, Peter H. McmurryAbstract:Abstract Previous work ( Ahn and Liu (1990) J. Aerosol. Sci. 21, 249–261; Brockmann (1981) Ph.D. Thesis, University of Minnesota; Rebours et al. (1992) J. Aerosol. Sci. 23, S189–S192; Stolzenburg (1988) Ph.D. thesis, University of Minnesota) has shown that for particles smaller than about 15 nm, pulse heights produced by the optical detector in a white-light ultrafine Condensation Nucleus counter (UCNC; Stolzenburg and McMurry (1991) Aerosol. Sci. Technol. 14, 48–65) decrease with initial particle size. We have previously reported on the use of pulse heights from this instrument to determine the concentrations of freshly nucleated atmospheric nanoparticles in the 3–4 nm diameter range ( Weber et al. (1995) J. Atm. Sci. 52, 2242–2257; Weber et al. (1997) J. Geophys. Res. 102, 4375–4385). In this paper we report on the inversion of measured pulse-height distributions to obtain size distributions of particles in the 3–10 nm diameter range. Using methods developed by Stolzenburg ( Stolzenburg (1988) Ph.D. Thesis, University of Minnesota) the effect of diffusional broadening is taken into account so as to obtain monodisperse kernel functions from measured pulse-height distributions produced by DMA-generated calibration aerosols in the 3–50 nm diameter range. These kernel functions are then used with the MICRON algorithm described by Wolfenbarger and Seinfeld (1990, J. Aerosol. Sci. 21, 227–247) to obtain size distributions of nanoparticle aerosols from measured pulse height distributions. Calculations were done to ensure that assumed pulse-height data generated from selected known size distributions can be inverted to recover the original size distribution. Results from these validation studies are discussed. Applications of the inversion algorithm to data acquired in studies of homogeneous nucleation in the atmosphere are also presented.
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Ultrafine Aerosol Measurement Using a Condensation Nucleus Counter with Pulse Height Analysis
Aerosol Science and Technology, 1996Co-Authors: M. T. Saros, Rodney J. Weber, James Marti, Peter H. McmurryAbstract:ABSTRACT Photodetector pulse heights from an ultrafine Condensation Nucleus counter increase monotonically with particle size in the ∼ 2.7–15 nm diameter range. This relationship can be used to measure concentrations and size distributions of ultrafine aerosols. In this study, we investigated the sensitivity of size-dependent pulse heights to total particle concentration, absolute pressure (0.25–1 atmosphere), and particle composition (H2SO4, (NH4)2SO4, NaCl, and tungsten oxide). We found that pulse heights shifted significantly with pressure and slightly with concentration. Coincidence led to errors for concentrations exceeding 4 × 103 cm−3. Over the range of conditions investigated, however, the observed shifts in the pulse height voltage were independent of size. The pulse height method is particularly applicable to situations involving low ultrafine particle concentrations, such as are encountered in the remote troposphere.
Markus D. Petters - One of the best experts on this subject based on the ideXlab platform.
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A single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity – Part 3: Including surfactant partitioning
Atmospheric Chemistry and Physics, 2013Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:Abstract. Atmospheric particles can serve as cloud Condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Kohler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud Condensation Nucleus activity. The presented formulation incorporates analytical approximations of surfactant partitioning to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code.
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a single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity part 3 including surfactant partitioning
Atmospheric Chemistry and Physics, 2012Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:Abstract. Atmospheric particles can serve as cloud Condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Kohler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud Condensation Nucleus activity. The presented formulation incorporates analytical approximations of surfactant partitioning to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code.
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A single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity – Part 3: Including surfactant partitioning
Atmospheric Chemistry and Physics Discussions, 2012Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:Abstract. Atmospheric particles can serve as cloud Condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Köhler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud Condensation Nucleus activity. The presented formulation incorporates the analytical approximations introduced by Raatikainen and Laaksonen to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code. We apply this extended model to discuss several uncertainties that hinder our ability to precisely pinpoint the role of surface tension in cloud droplet activation with current measurement and data analysis approaches.
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A single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity – Part 2: Including solubility
Atmospheric Chemistry and Physics, 2008Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:The ability of a particle to serve as a cloud Condensation Nucleus in the atmosphere is determined by its size, hygroscopicity and its solubility in water. Usually size and hygroscopicity alone are sufficient to predict CCN activity. Single parameter representations for hygroscopicity have been shown to successfully model complex, multicomponent particles types. Under the assumption of either complete solubility, or complete insolubility of a component, it is not necessary to explicitly include that component's solubility into the single parameter framework. This is not the case if sparingly soluble materials are present. In this work we explicitly account for solubility by modifying the single parameter equations. We demonstrate that sensitivity to the actual value of solubility emerges only in the regime of 2×10 −1 –5×10 −4 , where the solubility values are expressed as volume of solute per unit volume of water present in a saturated solution. Compounds that do not fall inside this sparingly soluble envelope can be adequately modeled assuming they are either infinitely soluble in water or completely insoluble.
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a single parameter representation of hygroscopic growth and cloud Condensation Nucleus activity part 2 including solubility
Atmospheric Chemistry and Physics, 2008Co-Authors: Markus D. Petters, Sonia M. KreidenweisAbstract:The ability of a particle to serve as a cloud Condensation Nucleus in the atmosphere is determined by its size, hygroscopicity and its solubility in water. Usually size and hygroscopicity alone are sufficient to predict CCN activity. Single parameter representations for hygroscopicity have been shown to successfully model complex, multicomponent particles types. Under the assumption of either complete solubility, or complete insolubility of a component, it is not necessary to explicitly include that component's solubility into the single parameter framework. This is not the case if sparingly soluble materials are present. In this work we explicitly account for solubility by modifying the single parameter equations. We demonstrate that sensitivity to the actual value of solubility emerges only in the regime of 2×10 −1 –5×10 −4 , where the solubility values are expressed as volume of solute per unit volume of water present in a saturated solution. Compounds that do not fall inside this sparingly soluble envelope can be adequately modeled assuming they are either infinitely soluble in water or completely insoluble.
Ming-taun Leu - One of the best experts on this subject based on the ideXlab platform.
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Improved Cloud Condensation Nucleus Spectrometer
2010Co-Authors: Ming-taun LeuAbstract:An improved thermal-gradient cloud Condensation Nucleus spectrometer (CCNS) has been designed to provide several enhancements over prior thermal- gradient counters, including fast response and high-sensitivity detection covering a wide range of supersaturations. CCNSs are used in laboratory research on the relationships among aerosols, supersaturation of air, and the formation of clouds. The operational characteristics of prior counters are such that it takes long times to determine aerosol critical supersaturations. Hence, there is a need for a CCNS capable of rapid scanning through a wide range of supersaturations. The present improved CCNS satisfies this need. The improved thermal-gradient CCNS (see Figure 1) incorporates the following notable features: a) The main chamber is bounded on the top and bottom by parallel thick copper plates, which are joined by a thermally conductive vertical wall on one side and a thermally nonconductive wall on the opposite side. b) To establish a temperature gradient needed to establish a supersaturation gradient, water at two different regulated temperatures is pumped through tubes along the edges of the copper plates at the thermally-nonconductive-wall side. Figure 2 presents an example of temperature and supersaturation gradients for one combination of regulated temperatures at the thermally-nonconductive-wall edges of the copper plates. c) To enable measurement of the temperature gradient, ten thermocouples are cemented to the external surfaces of the copper plates (five on the top plate and five on the bottom plate), spaced at equal intervals along the width axis of the main chamber near the outlet end. d) Pieces of filter paper or cotton felt are cemented onto the interior surfaces of the copper plates and, prior to each experimental run, are saturated with water to establish a supersaturation field inside the main chamber. e) A flow of monodisperse aerosol and a dilution flow of humid air are introduced into the main chamber at the inlet end. The inlet assembly is designed to offer improved (relative to prior such assemblies) laminar-flow performance within the main chamber. Dry aerosols are subjected to activation and growth in the supersaturation field. f) After aerosol activation, at the outlet end of the main chamber, a polished stainless-steel probe is used to sample droplets into a laser particle counter. The probe features an improved design for efficient sampling. The counter has six channels with size bins in the range of 0.5- to 5.0-micron diameter. g) To enable efficient sampling, the probe is scanned along the width axis of the main chamber (thereby effecting scanning along the temperature gradient and thereby, further, effecting scanning along the supersaturation gradient) by means of a computer-controlled translation stage.
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Design and characterization of a horizontal thermal gradient cloud Condensation Nucleus spectrometer
Journal of Aerosol Science, 2008Co-Authors: Dan Zhang, Katharine F. Moore, Randall R. Friedl, Ming-taun LeuAbstract:We report the design and characterization of a continuous-flow horizontal thermal gradient cloud Condensation Nucleus spectrometer (CCNS). The calibration of supersaturation inside the CCNS chamber using monodisperse NaCl aerosols shows that it is important to experimentally determine the supersaturation profile of the instrument, rather than relying on theoretical calculations based on measurements of the temperature gradient. The latter method significantly overestimates the actual supersaturation, mainly because of the discrepancy between measured and actual temperature gradients and the non-ideality in droplet samplings. Laboratory experiments were also performed to validate the instrumental performance and to compare the cloud Condensation nuclei (CCN) activation results with theoretical predictions based on Kohler theory. In the current configuration, the operational range of the CCNS has been verified to be between 0.08% and 0.9% supersaturation, with potential for further range enhancement. Using a computer-controlled motorized sampling system, we have demonstrated that CCN activation experiments can be routinely performed with much higher time resolution, suggesting excellent potential of this CCNS instrument for airborne measurements.
Akinori Takami - One of the best experts on this subject based on the ideXlab platform.
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size segregated measurements of cloud Condensation Nucleus activity and hygroscopic growth for aerosols at cape hedo japan in spring 2008
Journal of Geophysical Research, 2010Co-Authors: Michihiro Mochida, Yasuyuki Kitamori, Shankar G. Aggarwal, Kimitaka Kawamura, Kazuhiko Miura, Chiharu Nishitahara, Akinori TakamiAbstract:[1] Size-segregated measurements of cloud Condensation Nucleus (CCN) activity and hygroscopic growth were performed simultaneously for sulfate-rich aerosols at Cape Hedo, Okinawa, Japan, in spring 2008. The CCN fractions as functions of particle size at water vapor supersaturations of 0.44%, 0.25%, and 0.10% had nearly stepwise increases, and the diameters for 50% activation of its maximum (dact) were close to that of (NH4)2SO4. The size-resolved hygroscopic growth factor g measured using a hygroscopicity tandem differential mobility analyzer at 85% relative humidity (RH) mainly showed unimodal and highly hygroscopic characteristics. The observed characteristics as well as aerosol mass spectrometer data suggest the dominance of internally mixed ammoniated sulfate-rich particles. A clear negative correlation between dact and median g (gmedian) was observed for Aitken-mode particles, and backward air mass trajectories indicate lower dact and higher g of the aerosols from China and the Pacific and the opposite tendency for those from Korea and Japan. The size dependence of gmedian suggests that less hygroscopic carbonaceous components were more enriched in Aitken-mode particles and therefore affect the CCN activity and hygroscopicity. The CCN activation diameters were predicted on the basis of gmedian using a core-shell model. The modeled activation diameters reasonably agreed with measured dact, suggesting that the surface tension lowering effect due to organics and the enhancement of bulk hygroscopicity at high RH due to sparingly soluble or polymeric compounds were small. The results suggest that CCN activity of sulfate-rich aerosol particles is predicted well in regional and global aerosol models without incorporating these effects.
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Size‐segregated measurements of cloud Condensation Nucleus activity and hygroscopic growth for aerosols at Cape Hedo, Japan, in spring 2008
Journal of Geophysical Research, 2010Co-Authors: Michihiro Mochida, Chiharu Nishita-hara, Yasuyuki Kitamori, Shankar G. Aggarwal, Kimitaka Kawamura, Kazuhiko Miura, Akinori TakamiAbstract:[1] Size-segregated measurements of cloud Condensation Nucleus (CCN) activity and hygroscopic growth were performed simultaneously for sulfate-rich aerosols at Cape Hedo, Okinawa, Japan, in spring 2008. The CCN fractions as functions of particle size at water vapor supersaturations of 0.44%, 0.25%, and 0.10% had nearly stepwise increases, and the diameters for 50% activation of its maximum (dact) were close to that of (NH4)2SO4. The size-resolved hygroscopic growth factor g measured using a hygroscopicity tandem differential mobility analyzer at 85% relative humidity (RH) mainly showed unimodal and highly hygroscopic characteristics. The observed characteristics as well as aerosol mass spectrometer data suggest the dominance of internally mixed ammoniated sulfate-rich particles. A clear negative correlation between dact and median g (gmedian) was observed for Aitken-mode particles, and backward air mass trajectories indicate lower dact and higher g of the aerosols from China and the Pacific and the opposite tendency for those from Korea and Japan. The size dependence of gmedian suggests that less hygroscopic carbonaceous components were more enriched in Aitken-mode particles and therefore affect the CCN activity and hygroscopicity. The CCN activation diameters were predicted on the basis of gmedian using a core-shell model. The modeled activation diameters reasonably agreed with measured dact, suggesting that the surface tension lowering effect due to organics and the enhancement of bulk hygroscopicity at high RH due to sparingly soluble or polymeric compounds were small. The results suggest that CCN activity of sulfate-rich aerosol particles is predicted well in regional and global aerosol models without incorporating these effects.