Submicron aerosol distributions and CCN concentration at Gosan and Seoul, Korea

Submicron aerosol size distributions and total particle (i.e., condensation nuclei, CN) concentrations and cloud condensation nuclei (CCN) concentrations were measured at Gosan, Jeju Islands, Korea, in August 2006. A TSI SMPS model 3936L10 was used to measure aerosol size distributions every 3 minute, and a TSI CPC model 3010 and a model 3025 were used to measure the concentrations of aerosols having diameters larger than 10 nm and 3 nm, respectively, every 1 minute. CCN concentrations at 0.2%, 0.4%, 0.6%, 0.8% and 1.0% supersaturations (S) were measured every 25 minutes with a Droplet Measurement Technologies (DMT)¢¢ç¯ CCN Counter. Complete CCN spectra (0.02-1% S) were also measured with the two Desert Research Institute (DRI) instantaneous CCN spectrometers every 20 seconds. The Gosan site is located on a cliffy hill (approx. 50 m ASL) at the western tip of the Jeju Islands¢¢ç¯ coastline. The site is one of the key locations to monitor the influence of Asian continental outflow. Measurements were made in an instrument shelter from August 19^{th} to August 31^{st}. For the aerosols having diameter larger than 3 nm, its number concentrations were usually in the range of 5000 - 15000 cm-3. Occasionally the abrupt increases in the concentration were recorded near the noon time, with their peak concentration reaching several tens of thousands per cubic centimeter and lasting 2 to 5 hours. Such increases were due to the increased concentrations of aerosols having diameter between 3 nm and 10 nm, implying that the secondary aerosol formation and growth was taking place over the site during such periods. The geometric mean diameter (Dg) of aerosols having diameters between 10 and 500 nm usually fell in the range of 50 - 150 nm but it was as low as 20 nm during the aerosol formation events. For the CCN measurements, the two sets of instruments (DRI and DMT) having different measuring principle agreed well. CCN concentrations at 1 % S measured by the DMT CCN Counter fell in the range of 400 - 8000 cm-3. The CCN/CN ratios were below 1 for the whole period and were low when Dg were low and high when the Dg were high showing that the CCN measurements were consistent with other aerosol measurements. Additional measurement will be made in Seoul, the capital of Korea, with 10 million inhabitants, in September and October 2006. Further analysis and comparison including Seoul measurements will be presented at the conference.