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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-516
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
19 Jun 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Influence of common assumptions regarding aerosol composition and mixing state on predicted CCN concentration
Manasi Mahish1, Anne Jefferson2,3, and Don Collins1 1Department of Atmospheric Sciences, Texas A&M University, College Station, Texas, USA
2Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado, Boulder, CO, USA
3NOAA Earth System Research Laboratory, Boulder, CO, USA
Abstract. A 4-year record of aerosol size and hygroscopic growth factor distributions measured at the Department of Energy’s SGP ARM site in Oklahoma, U.S. were used to estimate supersaturation (S)-dependent cloud condensation nuclei concentrations (NCCN). Baseline or reference NCCN(S) spectra were estimated by using the data to create a matrix of size- and hygroscopicity-dependent number concentration (N) and then integrating for S > critical supersaturation (Sc) calculated for the same size and hygroscopicity pairs using κ-Köhler Theory. The accuracy of those estimates was assessed through comparison with the directly measured NCCN at the same site. Subsequently, NCCN was calculated using the same dataset but with an array of simplified treatments in which the aerosol was assumed to be either an internal or an external mixture and the hygroscopicity either assumed or based on averages derived from the growth factor distributions. The CCN spectra calculated using the simplified treatments were compared with those from the baseline approach to evaluate the impact of commonly used approximations. Among the simplified approaches, assuming the aerosol is an internal mixture with size-dependent hygroscopicity parameter (κ) resulted in estimates closest to those from the baseline approach over the range in S considered.

Citation: Mahish, M., Jefferson, A., and Collins, D.: Influence of common assumptions regarding aerosol composition and mixing state on predicted CCN concentration, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-516, in review, 2017.
Manasi Mahish et al.
Manasi Mahish et al.
Manasi Mahish et al.

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