Dependence of CCN activity of less volatile particles on the amount of coating observed in Tokyo

Abstract

A novel observation system has been developed to measure cloud condensation nuclei (CCN) activity simultaneously with volatility of aerosol particles at 400°C. CCN/CN ratios were measured using a CCN counter and a condensation particle counter, and volatility was measured with a volatility tandem differential mobility analyzer (VTDMA). This system was connected to a hygroscopicity tandem differential mobility analyzer in tandem to measure these properties of hygroscopicity-selected particles. These instruments were deployed in Tokyo in November 2004. In Tokyo, the dominant fraction of nonvolatile cores at 400°C has been found to be black carbon (BC). Therefore the number size distribution measured by VTDMA represents the mixing state of black carbon particles. The VTDMA measurement of hygroscopicity-selected particles revealed that most of the less hygroscopic particles were less volatile, while more hygroscopic particles were more volatile. CCN/CN ratios of less volatile particles [(CCN/CN) LV ] are estimated from CCN activity and volatility measurements of less hygroscopic particles. (CCN/CN) LV at SS = 0.5% is correlated with the decrease of peak diameter due to volatilization (Δdm), and (CCN/CN) LV is nearly equal to unity at Δd m = 10 nm. This result suggests that the CCN activity of BC particles significantly depends on the amount of coating. Copyright 2007 by the American Geophysical Union.