Charge-regulated aerosol survival from new particle formation to cloud condensation nuclei

Abstract. Cloud condensation nuclei (CCN) links atmospheric aerosol particles to cloud droplet formation, yet the electrical charge carried by these particles is not represented in aerosol-cloud models. Previous studies linking ionisation to CCN have focused on ion-induced particle production and found small effects. Here we test whether charge instead modifies particle survival and redistribution during growth to cloud-active sizes. Using the charge- and size-resolved ELSA-ICAM box model, we perform matched neutral and charged simulations in two regimes: a polluted urban regime dominated by sulfuric acid-dimethylamine nucleation and a clean boreal regime dominated by biogenic highly oxygenated organic molecule nucleation. In the polluted regime, bipolar charging reduces total particle number by 3.1 % relative to the neutral case at 72 h while increasing CCN at 0.2 % supersaturation by 2.5 %. By 120 h, the number response reverses to +4.1 % and the CCN enhancement increases to +5.8 %. In the clean regime, the charge-resolved case increases CCN by +8.9 % at 120 h relative to the neutral case. Process attribution shows that charge-dependent coagulation is the largest shared contribution, increasing CCN by +5.8 % in polluted air and +5.3 % in clean air through size-selective survival and redistribution. Ion-induced nucleation is negligible in polluted air but contributes an additional +3.6 % to CCN in clean air, despite producing a larger increase in particle number. The CCN response is therefore less sensitive to ion production than particle production. These results identify charge-regulated aerosol survival as a microphysical pathway linking atmospheric ionisation to CCN.