The kinetic multilayer model of multiphase chemistry (KM3C) resolves mass transport and chemical reaction in aerosol particles explicitly in depth. In this application it is used to simulate the growth of atmospheric nanoparticles by condensation of organic vapors, starting from a freshly nucleated cluster.
The condensable vapors are described by a volatility distribution: the gas-phase number concentration of organic compounds is specified for each decadic volatility class, labelled by its saturation mass concentration C* at 298 K, from 10−9 to 107 µg m−3. Volatilities are shifted with temperature following the Clausius-Clapeyron equation, so lowering the temperature makes a given distribution effectively less volatile and enhances growth. Working against this, uptake into a viscous particle is limited by slow surface-to-bulk transport and bulk diffusion, set by the bulk diffusion coefficient Db. The competition between the two effects buffers the growth rate, which is why observed growth rates cluster around a few nanometers per hour across widely different atmospheric conditions.
The simulation returns the particle diameter and the growth rate as a function of time. The growth rate is shown against particle diameter and can be downloaded as CSV, together with the two summary quantities: the growth rates between 1.5 – 3 nm (GR1.5–3) and 3 – 7 nm (GR3–7).
Note to Users: if you use results from the KM3C model, please cite the publication listed below and this website giving the URL https://www.multiphasekinetics.org/km3c/nano.
The model available on this site is an implementation of KM3C used in Zhang et al. (2026), offered here with a selected set of model input parameters. The default scenarios reproduce the conditions of CERN CLOUD chamber experiments investigating the dark ozonolysis of α-pinene (Stolzenburg et al., 2018) and of ambient measurements at the SMEAR II station in Hyytiälä, Finland (Stolzenburg et al., 2025). Vapor concentrations used here were taken from the original publications. The model offered on this website is functionally identical with the model used in our publication Zhang et al. (2026) for simulating the CERN CLOUD experiments. The simulations for the Hyytiälä field experiment in the paper used time-dependent gas-phase concentrations and prescribed the molar mass of compounds in each volatility bin based on measured data. The default scenarios available above represent time averages of the volatility distributions published in Stolzenburg et al. (2025). Further capabilities of the model will be made available over time.
Please contact us if you have any comments, questions, suggestions or ideas for collaboration.
Zhang, Z., Kang, H. G., Pöschl, U., and Berkemeier, T.: Buffering of atmospheric nanoparticle growth by temperature-dependent shifts in molecular composition, volatility and diffusivity, Atmos. Chem. Phys. 26, 12037–12047, (2026).