CCN activity of anthropogenically/biogenically influenced aerosol particles downwind of the Sacramento area during the CARES

NARUKI HIRANUMA, Daniel Cziczo, Danny Nelson, Qi Zhang, Ari Setyan, Chen Song, Manish Shrivastava, John Shilling

Pacific Norhwest National Laboratory

     Abstract Number: 708
     Last modified: April 5, 2011

Abstract
This study focuses on the characterization of cloud condensation nuclei (CCN) activity of aerosol particles measured during the Carbonaceous Aerosols and Radiative Effects Study (CARES) near Sacramento, CA in June 2010. Supersaturation-dependant CCN activity ( 0.1 - 0.5% supersaturation) was measured with commercial CCN counters at two locations; one near the city center (T0) and the other in Cool, CA, a small town ~ 40 kilometers downwind of the urban plume in the Sierra Nevada foothills (T1). Combined with particle size distribution (PSD) data, our CCN data was used to iteratively compute a polydisperse PSD derived hygroscopicity parameter, k$_p. Preliminary analysis indicates that k$_p was substantially higher when the urban aerosol plume was influenced by Bay Area emissions while the aerosol plume solely influenced by biogenic sources exhibited lower CCN activity. The relationship between the chemical composition and CCN activity of the aerosol will be discussed. Our analysis also suggests that there may have been an enhancement of CCN activity of aged urban aerosol plume as it was transported into the biogenically influenced foothills. The physical and chemical transformations of particles aged in the foothills as well as the diurnal profiles of CCN both at T0 and T1 will also be discussed for the transport events of June 15$^(th), 19$^(th), 23$^(rd), and 28$^(th).