The Impact of Ship-Produced Aerosols on the Microstructure and Albedo of Warm Marine Stratocumulus Clouds: A Test of MAST Hypotheses 1i and 1ii
MetadataShow full item record
Anomalously high reflectivity tracks in stratus and stratocumulus sheets associated with ships (known as ship tracks) are commonly seen in visible and near-infrared satellite imagery. Until now there have been only a limited number of in situ measurements made in ship tracks. The Monterey Area Ship Track (MAST) experiment, which was conducted off the coast of California in June 1994, provided a substantial dataset on ship emissions and their effects on boundary layer clouds. Several platforms, including the University of Washington C-131A aircraft, the Meteorological Research Flight C-130 aircraft, the National Aeronautics and Space Administration ER-2 aircraft, the Naval Research Laboratory airship, the Research Vessel Glorita, and dedicated U.S. Navy ships, participated in MAST in order to study processes governing the formation and maintenance of ship tracks. This paper tests the hypotheses that the cloud microphysical changes that produce ship tracks are due to (a) particulate emission from the ship’s stack and/or (b) sea-salt particles from the ship’s wake. It was found that ships powered by diesel propulsion units that emitted high concentrations of aerosols in the accumulation mode produced ship tracks. Ships that produced few particles (such as nuclear ships), or ships that produced high concentrations of particles but at sizes too small to be activated as cloud drops in typical stratocumulus (such as gas turbine and some steam-powered ships), did not produce ship tracks. Statistics and case studies, combined with model simulations, show that provided a cloud layer is susceptible to an aerosol perturbation, and the atmospheric stability enables aerosol to be mixed throughout the boundary layer, the direct emissions of cloud condensation nuclei from the stack of a diesel-powered ship is the most likely, if not the only, cause of the formation of ship tracks. There was no evidence that salt particles from ship wakes cause ship tracks.
Showing items related by title, author, creator and subject.
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.; Durkee, Phillip A. (1999-12-27);Ship tracks are a natural laboratory to isolate the effect of anthropogenic aerosol emissions on cloud properties. The Monterey Area Ship Tracks (MAST) experiment in the Pacific Ocean west of Monterey, California, in ...
Dietrich, Nathan S. (Monterey, California. Naval Postgraduate School, 2001-06);Military commanders require situational awareness to support real-time decis ion-making. To obtain information on possibly hostile entities in an area of interest, surveillance systems, which receive information from sensors ...
Noone, Kevin J.; Johnson, Doug W.; Taylor, Jonathan P.; Ferek, Ronald J.; Garrett, Tim; Hobbs, Peter V.; Durkee, Philip A.; Nielsen, Kurt; Öström, Elisabeth; O'Dowd, Colin; Smith, Michael H.; Russell, Lynn M.; Flagan, Richard C.; Seinfeld, John H.; De Bock, Lieve; Van Grieken, René E.; Hudson, James G.; Brooks, Ian; Gasparovic, Richard F.; Pockalny, Robert A. (2000);A case study of the effects of ship emissions on the microphysical, radiative, and chemical properties of polluted marine boundary layer clouds is presented. Two ship tracks are discussed in detail. In situ measurements of ...