Aircraft measurement of vertical and horizontal distributions of aerosol and cloud condensation nuclei (CCN) number concentrations in and around the Korean Peninsula

Two aircraft campaigns (Sept. 30 – Oct. 18, 2009 and June 8 – 17, 2011) were conducted to measure the vertical aerosol number concentration (NCN) and cloud condensation nuclei (CCN) number concentration at 0.6% supersaturation (NCCN) over the western (Yellow Sea) and eastern (East Sea) seas of the Korean Peninsula. All vertical soundings were classified into three regions: the Yellow Sea, the west coast of the Korean Peninsula and the East Sea, and there were 6, 12 and 6 soundings, respectively, in each region. The average NCN were higher over the Yellow Sea than over the East Sea (9000 cm-3 vs. 3000 cm-3), revealing the east to west gradient of the aerosol concentration in this region. Vertically it was higher at the lower altitudes that extended to the boundary layer top. The average NCCN/NCN ratios were 0.67, 0.67 and 0.75, respectively, for the three regions and these ratios were fairly constant over the whole altitude range for all three regions. Frequent particle formation events were found to occur on non-rainy days over the Yellow Sea while none was observed over the East Sea. These were indirectly inferred by examining the NCCN/NCN ratio since this ratio was very low during the particle formation events because newly formed very small particles could not become CCN. In some cases, simultaneous SMPS measurements at the surface sites of Anmyeon (at the west coast of the Korean Peninsula) and Gosan (Jeju Island, south of the Korean Peninsula) both confirmed that such events actually occurred. This also implied that the particle formation events occurred at least over 150 km by 350 km areal extent. In some other cases, such events occurred in the free atmosphere without reaching down to the surface. Some more details and their comparison to the measurements at the surface sites in and around the Korean Peninsula will be shown at the conference.