Inter-comparison of aerosol hygroscopic properties as measured by several instruments in the summer 2011 Aerosol Lifecycle IOP

Description

The Aerosol Lifecycle IOP at Brookhaven National Laboratory deployed three instruments that measured various hygroscopic properties of ambient aerosols. The first instrument is an HT-DMA (Humidified Tandem Differential Mobility Analyzer), which measures the growth in aerosol size when subjected to 90% relative humidity. The second is a Humidigraph, or f(r), which measures the change in aerosol optical scattering due to a change in humidity. The third is a CCN (Cloud Condensation Nuclei Counter), which measures the ability of aerosol particles to form cloud condensation nuclei. These hygroscopic properties are important in assessing the effect of aerosols on global change. The HT-DMA (Brechtel Manufacturing, Inc.) and Humidigraph (Pacific Northwest National Laboratory) are newly developed instruments being deployed for the first time in the aerosol observing systems (AOS) of the second ARM Mobile Facility, Tropical Western Pacific site, and Mobile AOS-A (MAOS-A).

The Aerosol Lifecycle field campaign occurred from June 15 to August 15, 2011. One of the more interesting days was the period of August 2–3, when two subsequent atmospheric plumes were sampled. These plumes (A and B) differed in organic aerosol content, source region (plume B from biomass burning region in Canada), percentage of aged aerosol, and number concentration. These two plumes also differed in aerosol hygroscopicity, which makes for an interesting inter-comparison between the three “hygroscopicity” instruments. The inter-comparison makes use of data from an SMPS (Scanning Mobility Particle Sizer), a CPC (Condensation Particle Counter), and a UHSAS (Ultra=High Sensitivity Aerosol Spectrometer), all of which were also deployed during the IOP.