Time lag effects on the binary homogeneous nucleation of aerosols in the wake of an aircraft

Steady state rates and time lags for binary homogeneous nucleation of sulfuric acid‐water aerosols in aircraft wakes are calculated for relative humidities lower than 100%, i.e., for the case in which no visible contrails form. Formation of the sulfuric acid‐water aerosol is shown to depend sensitively on the concentration of sulfuric acid derived from engine exhaust. Nucleation of the sulfuric acid‐water aerosol is found to be controlled both by the steady state rate and by the time lag on the timescales relevant to contrail formation. Only for the highest gas‐phase acid concentrations are the nucleation time lags sufficiently short that steady state conditions pertain.