Aerosol dynamics in ship tracks

• Published in: Journal of Geophysical Research (0148-0227) Vol. 104; no. D24; p. 31
• Main Authors: Russell, Lynn M, Seinfeld, John H, Flagan, Richard C, Ferek, Ronald J, Hegg, Dean A, Hobbs, Peter V, Wobrock, Wolfram, Flossmann, Andrea I, O'Dowd, Colin D, Nielsen, Kurt E
• Format: Journal Article
• Language: English
• Published: 27-12-1999
• ISSN: 0148-0227

The Monterey Area Ship Tracks (MAST) experiment in the Pacific Ocean west of Monterey, California, in June 1994, provides an unprecedented data set for evaluating our understanding of the formation and persistence of the anomalous cloud features that characterize ship tracks. The data set includes conditions in which the marine boundary layer is both clean and continentally influenced. Two case studies during the MAST experiment are examined with a detailed aerosol microphysical model that considers an external mixture of independent particle populations. The model allows tracking individual particles through condensational and coagulational growth to identify the source of cloud condensation nuclei (CCN). In addition, a cloud microphysics model was employed to study specific effects of precipitation. Predictions and observations reveal important differences between clean (particle concentrations below 150 cu cm) and continentally influenced (particle concentrations above 400/cu cm) background conditions: in the continentally influenced conditions there is a smaller change in the cloud effective radius, drop number, and liquid water content in the ship track relative to the background than in the clean marine case. Predictions of changes in cloud droplet number concentrations and effective radii are consistent with observations, although there is significant uncertainty in the absolute concentrations due to a lack of measurements of the plume dilution. (Author)