Evolution of aircraft-generated volatile particles in the far wake regime:Potential contributions to ambient CCN IN

We apply a detailed aerosol microphysics model to study the evolution of ae rosols in the far wake of an aircraft plume. Constrained by in-situ measure ments, our simulations reveal:that the largest volatile particles-those mos t likely to contribute to the background abundance of condensation nuclei-a re dominated by ion-mode aerosols formed on chemi-ions. By tracking the evo lution of the aircraft-generated particles from the near wake to the far wa ke, we estimate the properties:of the aircraft particles that are effective ly injected into the upper troposphere. The entrainment of ambient vapors a nd aerosols into the aging plume is taken into account, which significantly affects the outcome. The model calculations reveal that a substantial numb er of the larger ion-mode volatile particles may survive long enough to act as potential cloud nuclei, thus perturbing the background CCN population. This perturbation is significant during the winter season, and in other loc ales with low background aerosol concentrations, but is likely to be neglig ible during the summer season or at locations with heavy aerosol loading. T he implications and uncertainties of the results are discussed.