title: Surface fractal dimension, water adsorption efficiency, and cloud nucleation activity of insoluble aerosol.
abstract: Surface porosity affects the ability of a substance to adsorb gases. The surface fractal dimension D is a measure that indicates the amount that a surface fills a space, and can thereby be used to characterize the surface porosity. Here we propose a new method for determining D, based on measuring both the water vapour adsorption isotherm of a given substance, and its ability to act as a cloud condensation nucleus when introduced to humidified air in aerosol form. We show that our method agrees well with previous methods based on measurement of nitrogen adsorption. Besides proving the usefulness of the new method for general surface characterization of materials, our results show that the surface fractal dimension is an important determinant in cloud drop formation on water insoluble particles. We suggest that a closure can be obtained between experimental critical supersaturation for cloud drop activation and that calculated based on water adsorption data, if the latter is corrected using the surface fractal dimension of the insoluble cloud nucleus.
authors.affiliation: Finnish Meteorological Institute, 00101 Helsinki, Finland.|Department of Applied Physics, University of Eastern Finland, 70211 Kuopio, Finland.
authors.forename: Ari
authors.initials: A
authors.lastname: Laaksonen
authors.affiliation: Department of Applied Physics, University of Eastern Finland, 70211 Kuopio, Finland.
authors.forename: Jussi
authors.initials: J
authors.lastname: Malila
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.|School of Chemical &Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.|Institute for Environmental Research &Sustainable Development, National Observatory of Athens (NOA), I. Metaxa &Vas. Pavlou, 15236 Palea Penteli, Greece.|Institute of Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Stadiou Str., Platani, GR-26504 Patras, Greece.
authors.forename: Athanasios
authors.initials: A
authors.lastname: Nenes
authors.affiliation: Department of Atmospheric Sciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Hui-Ming
authors.initials: HM
authors.lastname: Hung
authors.affiliation: Department of Atmospheric Sciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Jen-Ping
authors.initials: JP
authors.lastname: Chen