AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Aerosol Hygroscopicity in a Mixed-Deciduous Forest During CABINEX 2009
George R. Mwaniki, Rosenkrance Chelsea, Mark E. Erupe, Shelley Pressley, TIMOTHY M. VANREKEN, Washington State University
Abstract Number: 211 Working Group: Remote and Regional Atmospheric Aerosols
Abstract During Summer 2009 the Community Atmosphere-Biosphere Interactions EXperiment (CABINEX) was carried out at the PROPHET research facility at the University of Michigan Biological Station (UMBS). The PROPHET site at UMBS is a forested atmospheric chemistry research station located in the northern part of Michigan’s Lower Peninsula; its remote location offers a unique opportunity to study atmospheric chemistry in a region dominated by biogenic emissions of volatile organic compounds. However, despite a 15+ year history of atmospheric chemistry field work at PROPHET, virtually no aerosol measurements had been reported at the site prior to the 2009 CABINEX campaign. During CABINEX, we measured several aerosol physical and chemical properties at the site, including particle size distribution, bulk aerosol water-soluble composition, CCN concentration at five supersaturations, and the aerosol scattering coefficient.
Here we present an overview of the aerosol properties during CABINEX and a detailed hygroscopic closure analysis for the study period. We calculated the hygroscopicity parameter (к) of the aerosol using two distinct approaches: 1) by comparing the measured CCN concentration at a given supersaturation to the particle size distribution; and 2) using measurements of aerosol water-soluble composition along with reasonable approximations of aerosol properties that were not directly measured. The к-values resulting from these two approaches are compared. Wet aerosol volumes are also calculated using these calculated к-values and compared to observations of aerosol scattering coefficient. Finally, the observed variability in aerosol hygroscopicity is related to broader patterns in meteorological conditions and atmospheric pollution.