Figure 11.

Contribution to the uncertainty in monthly average CCN_0.2 based on HadGEM3-UKCA perturbed parameter ensemble simulations for the year 2008. Each color refers to 1 of the 26 perturbed parameters as indicated in the legend of the figure. The uncertainty is shown as the percentage contribution of the parameter to the CCN_0.2 variance. The assumed parameter uncertainty ranges are given in Yoshioka et al. (2019). All contributions smaller than 1% are not shown. Abbreviations are as follows. BL_Nuc: boundary layer nucleation; Aging: aging “rate” from insoluble to soluble; Acc_Width: modal width (accumulation soluble–insoluble); Ait_Width: modal width (Aitken soluble–insoluble); Cloud_pH: pH of cloud drops; Carb_FF_Ems: particle mass emission rate for BC and OC (fossil fuel); Carb_BB_Ems: particle mass emission rate for BC and OC (biomass burning); Carb_Res_Ems: particle mass emission rate for BC and OC (biofuel); Carb_FF_Diam: particle emitted mode diameter for BC and OC (fossil fuel); Carb_BB_Diam: particle emitted mode diameter for BC and OC (biomass burning); Carb_Res_Diam: particle emitted mode diameter for BC and OC (biofuel); Prim_SO4_Frac: mass fraction of SO₂ converted to new ${\text{SO}}_4^{-2}$ particles in sub-grid power plant plumes; Prim_SO4_Diam: mode diameter of new sub-grid ${\text{SO}}_4^{-2}$ particles; Sea_Spray: sea spray mass flux (coarse / accumulation); Anth_SO2: SO₂ emission flux (anthropogenic); Volc_SO2: SO₂ emission flux (volcanic); BVOC_SOA: biogenic monoterpene production of SOA; DMS: DMS emission flux; Dry_Dep_Ait: dry deposition velocity of Aitken mode aerosol; Dry_Dep_Acc: dry deposition velocity of accumulation-mode aerosol; Dry_Dep_SO2: dry deposition velocity of SO₂; Kappa_OC: hygroscopicity parameter kappa for organic aerosols. Default value in UKCA is 0.06; see Petters and Kreidenweis (2007). Sig_W: standard deviation of updraft velocity (this affects the activation of aerosol particles to form cloud droplets). Dust: dust emission flux; Rain_Frac: the fraction of the cloudy part of the grid box in which rain is forming and hence scavenging takes place; Cloud_Ice_Thresh: scavenging (by both cloud liquid and ice water) is suppressed in dynamic clouds when cloud ice fraction is higher than this value. The parameters with no color in the legend do not contribute to the uncertainty in CCN_0.2 (less than 1 %) at any station in any month.