Measurements of nanoparticle number size distribution to study new particle formation and growth in Yongin, Korea during the KORUS-AQ campaign

We measured the particle size distribution using a Scanning Mobility Particle Sizer (SMPS) during the KORea-US Air Quality Study (KORUS-AQ) campaign from May to June 2015 at 10 minute intervals. SMPS measures the number size distribution between 5 and 351 nm in 89 channels. We also measured the meteorological parameter such as wind direction and speed, relative humidity, temperature using an automatic weather system at 30 minute intervals. The measurement site is located at the rooftop of a five-story building on the hill (37.34 °N, 127.27 °E, 167 m above sea level), about 35 km southeast of downtown Seoul, which is affected by prevailing northwesterlies. There are no major emission sources nearby except a 4-lane road running about 1.4 km to the west. Particle formation was determined by the increase in the number concentration of nucleation mode whose diameter is less than or equal to 20 nm for more than an hour. Particle growth was determined by continuous increase of the number concentration and size. We compared the difference in number size distribution between event days and non-event days for the whole measured period. Occurrences of particle formation and growth were discussed in association with meteorological data.