“…It is known that sub-grid scale nucleation occurs in both volcanic and industrial plumes (Allen et al, 2002;Brock et al, 2002), hence in the model we include 2.5 % of the emitted SO 2 as sub-grid sulphate adding to particle number and mass in the accumulation and coarse modes (also used by Stier et al, 2005). Measurements of near-source sulphate particles at several continuously degassing volcanoes indicate a fraction of 1 % to 5 % of the total emitted SO 2 (e.g., Allen et al, 2002;Mather et al, 2003aMather et al, , b, 2004Mather et al, , 2006Mather et al, , 2012Martin et al, 2008). Luo and Yu (2011) have shown that global CCN number concentrations are sensitive to both the sub-grid sulphate mass fraction and the assumptions made about its size distribution, amongst many other aerosol processes.…”