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

[1] A novel observation system has been developed to measure cloud condensation nuclei (CCN) activity simultaneously with volatility of aerosol particles at 400 degrees 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 degrees 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 (Delta d(m)), and (CCN/CN)(LV) is nearly equal to unity at Delta d(m) = 10 nm. This result suggests that the CCN activity of BC particles significantly depends on the amount of coating.