We scrutinize the importance of aerosol water for the aerosol optical depth (AOD) calculations using a long-term evaluation of the EQuilibrium Simplified Aerosol Model v4 for climate modeling. EQSAM4clim is based on a single solute coefficient approach that efficiently parameterizes hygroscopic growth, accounting for aerosol water uptake from the deliquescence relative humidity up to supersaturation. EQSAM4clim extends the single solute coefficient approach to treat water uptake of multicomponent mixtures. The gas–aerosol partitioning and the mixed-solution water uptake can be solved analytically, preventing the need for iterations, which is computationally efficient. EQSAM4clim has been implemented in the global chemistry climate model EMAC and compared to ISORROPIA II on climate timescales. Our global modeling results show that (I) our EMAC results of the AOD are comparable to modeling results that have been independently evaluated for the period 2000–2010, (II) the results of various aerosol properties of EQSAM4clim and ISORROPIA II are similar and in agreement with AERONET and EMEP observations for the period 2000–2013, and (III) the underlying assumptions on the aerosol water uptake limitations are important for derived AOD calculations. Sensitivity studies of different levels of chemical aging and associated water uptake show larger effects on AOD calculations for the year 2005 compared to the differences associated with the application of the two gas–liquid–solid partitioning schemes. Overall, our study demonstrates the importance of aerosol water for climate studies.
|Original language||English (US)|
|Number of pages||28|
|Journal||Atmospheric Chemistry and Physics|
|State||Published - Nov 27 2018|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)–ERC grant agreement no. 226144 through the C8 Project, and by the Energy oriented Centre of Excellence (EoCoE), grant agreement number 676629, funded within the Horizon 2020 framework of the European Union. EMAC simulations have been carried out on the supercomputer of the German Climate Research Center and on the Cy-Tera cluster, operated by the Cyprus Institute (CyI) and co-funded by the European Regional Development Fund and the Republic of Cyprus through the Research Promotion Foundation (Project Cy-Tera NEA-YΠOΔOMH/ΣTPATH/0308/31). Model emissions were kindly provided by the anthropogenic emission inventory EDGAR Climate Change and Impact Research (CIRCE) through the EU FP6 project no. 036961. We thank the measurement and model development teams for providing the observations, numerical models, and many useful codes that have been used in this study.