Studies on physical-chemical processes of aerosol-cloud interaction

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Cloud condensation nuclei (CCN) activity is determined by aerosol diameter, fraction of water soluble components, and surface tension. We quantified CCN activities as a function of these parameters and related them with cloud formation processes.A)Controlling factors of CCN activities of aerosol in urban airWe measured chemical composition, mixing states, and CCN activity of aerosol in Tokyo using an aerosol mass spectrometer, black carbon (BC) instruments, and a CCN counter. We found that CCN activity of thickly coated BC is controlled by the chemical composition of water soluble compounds. The CCN activity of thinly coated BC is controlled by the thickness of the coating.B)Measurements of aerosol-cloud interactionWe conducted aircraft measurements of aerosol and cloud particles inside and outside of clouds located at 1-2 km near Japan in spring. We showed that thickly coated BC particles were taken up into clouds efficiently, consistent with the ground based measurements. This also s … More hows that BC can be a good tracer to quantitatively study aerosol-cloud interaction.C)Time constant of CCN formationWe showed that CCN activity of aerosol transported from the Asian continent within a few days is controlled mainly by the fraction of water soluble components from the data obtained in Jeju Island, Korea. Decrease in the surface tension of organic aerosol is also estimated to is contribute to the CCN activity. The CCN activity of various types of aerosol was measured also near Beijing. The observed CCN activity is consistent with the understandings obtained in Tokyo and Jeju Is.D)Calibration of the cloud probe and its aerodynamical characteristicsLight scattering cloud probe was calibrated using standard particles with high precision. We made aerodynamical calculations of airflows around the probe mounted on the aircraft and found high collection efficiency of cloud droplets.E)We calculated size distribution of cloud droplets predicted from various CCN concentrations using a trajectory model. Sensitivity of CCN-cloud interaction was estimated by the numerical experiments. Less