Characteristics of Aerosols, CCN and IN Abilities from Ground-Based Observations at Tsukuba, Japan

In order to characterize the abilities of atmospheric aerosols to act as cloud condensation nuclei (CCN) and ice nuclei (IN), we have conducted the ground-based monitoring observations since March 2012 at Tsukuba, Japan (36.06°N, 140.13°E), by using a CCN counter (CCNC), continuous-flow-diffusion-chamber type IN counter (INC), scanning mobility particle sizer (SMPS), optical particle counter (OPC), and aerodynamic particle spectrometer (APS).

The average number concentration of CCN was about 2,300 cm^-3 at a water supersaturation (SSw) of 0.5%. The CCN concentration showed the seasonal trends of higher in winter and lower in summer. The number concentration of IN was about 5 L^-1 on average at a temperature of -25 C over the range of SSw from 0 to 5%. The IN concentration had a large variability with some trends of higher in late spring or early summer.

The median values of hygroscopicity of aerosols were 0.1 (SSw=1.0%) to 0.35 (SSw=0.1%). Their median of ice nucleation active site (INAS) density was on the order of 10⁷ m^-2 from -15 to -35 C with weak dependency of temperature. The results in this study will be compared with previous studies.