1The Cyprus Institute, Nicosia, Cyprus
2Max Planck Institute for Chemistry, Mainz, Germany
3Eco-Serve, Freiburg, Germany
4Department of Earth System Science, University of California, Irvine, USA
5Atmospheric Science, University of Michigan, Ann Arbor, Michigan, USA
6Institute of Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Patras, Greece
7Schools of Earth and Atmospheric Sciences and Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
8Institute of Environmental Research and Sustainable Development, National Observatory of Athens, Palea Penteli, Greece
Received: 22 Oct 2015 – Discussion started: 27 Nov 2015
Abstract. We introduce a framework to efficiently parameterise the aerosol water uptake for mixtures of semi-volatile and non-volatile compounds, based on the coefficient, νi. This solute-specific coefficient was introduced in Metzger et al. (2012) to accurately parameterise the single solution hygroscopic growth, considering the Kelvin effect – accounting for the water uptake of concentrated nanometer-sized particles up to dilute solutions, i.e. from the compounds relative humidity of deliquescence (RHD) up to supersaturation (Köhler theory). Here we extend the νi parameterisation from single to mixed solutions. We evaluate our framework at various levels of complexity, by considering the full gas–liquid–solid partitioning for a comprehensive comparison with reference calculations using the E-AIM, EQUISOLV II and ISORROPIA II models as well as textbook examples. We apply our parameterisation in the EQuilibrium Simplified Aerosol Model V4 (EQSAM4clim) for climate simulations, implemented in a box model and in the global chemistry–climate model EMAC. Our results show (i) that the νi approach enables one to analytically solve the entire gas–liquid–solid partitioning and the mixed solution water uptake with sufficient accuracy, (ii) that ammonium sulfate mixtures can be solved with a simple method, e.g. pure ammonium nitrate and mixed ammonium nitrate and (iii) that the aerosol optical depth (AOD) simulations are in close agreement with remote sensing observations for the year 2005. Long-term evaluation of the EMAC results based on EQSAM4clim and ISORROPIA II will be presented separately.
Revised: 20 Apr 2016 – Accepted: 20 May 2016 – Published: 10 Jun 2016
Metzger, S., Steil, B., Abdelkader, M., Klingmüller, K., Xu, L., Penner, J. E., Fountoukis, C., Nenes, A., and Lelieveld, J.: Aerosol water parameterisation: a single parameter framework, Atmos. Chem. Phys., 16, 7213-7237, doi:10.5194/acp-16-7213-2016, 2016.