Individual-Particle Studies of Cloud Droplet Residues and Ambient Aerosols in RICO: Effects of Particle Size, Composition, Surface Properties and Mixing State on Trade-Wind Cumuli

Arizona State University, Scottsdale AZ

Investigators

Abstract

This project is part of a larger collaborative experiment called "Rain in Cumulus over the Ocean" (RICO), which will be conducted from November 2004 to January 2005 near Antigua. A primary RICO objective is to understand warm-rain formation, the formation of rain in clouds that do not reach the freezing level. To contribute to that goal, these investigators will determine the composition and concentration of particles present in the air where clouds and rain form. Large particles, with sizes of a few to tens of micrometers, are thought to play an especially important role in the initiation of rainfall from warm clouds. Using a research aircraft, the investigators will collect samples of such particles and analyze them using electron microscopy to determine their sizes, composition, and concentration. They will compare samples collected outside cloud to those obtained by evaporation of cloud droplets in cloud to help determine how particles influence the formation of cloud droplets and how the internal composition of the drops is modified while they are in cloud. The study will also assess the importance of mineral-dust particles, sea-salt particles, and particles containing elemental carbon and organic species. The results will be used by these investigators and others in RICO to understand how large aerosol particles influence the formation of rain in trade-wind Cumulus clouds.