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Published May 2013 | Supplemental Material + Published
Journal Article Open

Eastern Pacific Emitted Aerosol Cloud Experiment


Aerosol–cloud–radiation interactions are widely held to be the largest single source of uncertainty in climate model projections of future radiative forcing due to increasing anthropogenic emissions. The underlying causes of this uncertainty among modeled predictions of climate are the gaps in our fundamental understanding of cloud processes. There has been significant progress with both observations and models in addressing these important questions but quantifying them correctly is nontrivial, thus limiting our ability to represent them in global climate models. The Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) 2011 was a targeted aircraft campaign with embedded modeling studies, using the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft and the research vessel Point Sur in July and August 2011 off the central coast of California, with a full payload of instruments to measure particle and cloud number, mass, composition, and water uptake distributions. EPEACE used three emitted particle sources to separate particle-induced feedbacks from dynamical variability, namely 1) shipboard smoke-generated particles with 0.05–1-μm diameters (which produced tracks measured by satellite and had drop composition characteristic of organic smoke), 2) combustion particles from container ships with 0.05–0.2-μm diameters (which were measured in a variety of conditions with droplets containing both organic and sulfate components), and 3) aircraft-based milled salt particles with 3–5-μm diameters (which showed enhanced drizzle rates in some clouds). The aircraft observations were consistent with past large-eddy simulations of deeper clouds in ship tracks and aerosol– cloud parcel modeling of cloud drop number and composition, providing quantitative constraints on aerosol effects on warm-cloud microphysics.

Additional Information

© 2013 American Meteorological Society. In final form 9 August 2012. The E-PEACE field campaign and modeling studies were funded by the National Science Foundation (Grants AGS-1013423, AGS-1008848, AGS-1013381, AGS-1013319; ATM-0744636, AGS-0821599, and ATM-0349015) and the Office of Naval Research (Grants N00014-11-1-0783, N00014-10-1-0811, N00014-10-1-0200, and N00014-08-1-0465). Sea Spray Research, Inc. provided oil for the operation of the smoke generators. The authors gratefully acknowledge the crews of the CIRPAS Twin Otter and the R/V Point Sur for their assistance during the field campaign; Tom Maggard, who revived and tirelessly maintained the smoke generators during the cruise; David Malmberg and the crew of the R/V Sproul, for their assistance in testing the smoke generators prior to the campaign; Spyros Pandis, for providing the CCN spectrometer; and Daniel Rosenfeld, for providing the powdered salt. We also thank Richard Leaitch and two anonymous reviewers for providing helpful comments on the submitted manuscript.

Attached Files

Published - bams-d-12-00015.1.pdf

Supplemental Material - 10.1175_bams-d-12-00015.2.pdf


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