A journal article entitled Chemical Properties of Insoluble Precipitation Residue Particles by Jessie M. Creamean, Christopher Lee, Thomas C. Hill, Andrew P. Ault, Paul J. DeMott, Allen B. White, F. Martin Ralph, and Kimberly A. Prather, was published in the October 2014 issue of the Journal of Aerosol Science.
Aerosols serve as seeds for cloud droplet and ice crystal formation, and can thereby influence precipitation development. Higher concentrations of pollution aerosols are thought to suppress or delay the onset of precipitation, while aerosols such as mineral and soil dust can contain surface sites that lead to their involvement as ice nuclei (IN) and are thought to enhance precipitation formation.
Laboratory studies of aerosols that serve as cloud nuclei and in-cloud measurements of aerosol chemical composition provide information regarding which types of aerosols selectively serve as IN or CCN. Further, precipitation chemistry can provide unique insights into the composition of aerosol particles involved in precipitation processes. Until recently, precipitation chemistry studies focused predominantly on soluble components. Analyzing the single particle insoluble components in addition to soluble ions in precipitation can provide detailed information on the individual particles originally in the cloud or removed by precipitation as well as the source of the aerosols.
This paper presents an in-depth analysis of resuspended residues from precipitation samples collected at a remote site in the Sierra Nevada Mountains in California during the 2009-2011 winter seasons of the CalWater field campaign. This paper also presents results from laboratory control experiments of dust, leaf litter, smoke, and sea salt samples that were conducted to better understand how insoluble and soluble residues are distributed during the atomization process and aid in the classification of the residue compositions in the precipitation samples collected in the field. Further, IN measurements of insoluble residues from precipitation water enabled the determination of residue types that likely seeded clouds. Long-range transported dust mixed with biological material tended to be more IN active, while purely biological residues contained a variety of high and low temperature IN.
Knowledge of the precipitation chemistry of insoluble residues coupled with meteorological and cloud microphysical measurements will ultimately improve our understanding of the link between aerosols, clouds, and precipitation. The ability to confidently identify the chemical composition of particles in precipitation is important for understanding aerosol cloud droplet/crystal nucleation and wet removal mechanisms. When used in combination with meteorological and cloud microphysical property measurements, and ice nucleation measurements, precipitation residue chemistry can help determine the types of aerosols that are incorporated into clouds and which impact the formation of precipitation.
Contact: Jessie Creamean