Observations of ship tracks from ship-based platforms

Ship-based measurements in June 1994 provided information about ship-track clouds and associated atmospheric environment observed from below cloud lev els that provide a perspective different from satellite and aircraft measur ements. Surface measurements of latent and sensible heat fluxes, sea surfac e temperatures, and meteorological profiles with free and tethered balloons provided necessary input conditions for models of ship track formation and maintenance. Remote sensing measurements showed a coupling of ship plume d ynamics and entrainment into overlaying clouds. Morphological and dynamic e ffects were observed on clouds unique to the ship tracks. These morphologic al changes included lower cloud bases early in the ship-track formation, ev idence of raised cloud bases in more mature tracks, sometimes higher cloud tops, thin cloud-free regions paralleling the tracks, and often stronger ra dar returns. The ship-based lidar aerosol measurements revealed that ship p lumes often interacted with the overlying clouds in an intermittent rather than continuous manner. These observations imply that more must be learned about ship-track dynamics before simple relations between cloud condensatio n nuclei and cloud brightness can be developed.