Chemical Heterogeneity Among Fog Drop Populations and Its Influence on Aerosol Processing by Fogs

Colorado State University, Fort Collins CO

Investigators

Abstract

This research project consists of field stidues to examine the chemical heterogeneity among fog drop populations and the effects this heterogeneity exerts on aerosol and trace gas processing. The project involves the first deployments of two new cloud/fog samplers designed to provide better resolution of drop composition as a function of drop size. These samplers provide 3-stage droplet collection in supercooled clouds and 5-stage collection in warm clouds and fogs. The new multi-stage collectors will be deployed to measure drop size-resolved fog composition in two major field campaigns: in winter 2000/01 during the California Regional PM10/PM2.5 Air Quality Study (CRPAQS) intensive in the San Joaquin Valley and in winter 2001/02 in a study of aerosol processing by fogs in Denver's Brown Cloud. Results from both studies will represent a considerable advance in understanding of how fog drop composition varies across the drop size spectrum and the influence of this variation on aerosol formation (via gas uptake and aqueous sulfur oxidation) and removal (via drop deposition). The CRPAQS study will also provide the first good opportunity to test the ability of size-resolved fog chemistry models to accurately predict the size-dependent chemical composition of fogs. A new 2-stage stainless steel fog sampler will also be developed and deployed in both field campaigns. This instrument will provide the first reliable information about the distribution of organic carbon across the drop size spectrum and its influence on the ability of urban fogs to cleanse the atmosphere of organic aerosol particles by scavenging and deposition.