Minsu Park

Characteristics of submicron aerosol number size distribution and new particle formation events measured in Seoul, Korea, during 2004–2012

The diurnal and seasonal characteristics of the submicron aerosol size distribution measured in Seoul for a long term (2004–2012) were analyzed. The average diurnal variation of aerosol number size distribution showed a single modal distribution but the modal diameter varied around 35 nm and the total aerosol concentration varied diurnally with the maximum during the rush hour. To identify the dominant patterns of the diurnal variation of aerosol number size distribution, the cyclostationary empirical orthogonal function (CSEOF) method was employed. The first CSEOF mode revealed the dominant diurnal pattern that represented an urban life pattern. The principal component (PC) values of the first CSEOF mode showed clear seasonal variation. The PC values were the largest in winter months due to winter monsoon that brought polluted air masses from China, and larger traffic emission amount during the winter season. New particle formation (NPF) events were found to occur on 12.3% of the total measurement days in Seoul when classified with a subjective method. NPF frequency varied seasonally, with the maximum in spring. The second CSEOF mode was found to represent NPF events. A way to identify NPF event days by the CSEOF method was proposed and generally performed well but with some exceptions. The favorable conditions for NPF events in Seoul were found to be low RH, low condensation sink, and low cloud cover, which is consistent with some previous studies. Lastly, the relative contribution of NPF to ultrafine aerosol in Seoul was estimated to be ~32%.

Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment.

Aerosol measurement and study of new particle formation event in Seoul during 2004 - 2010

This study is based on 6-years measurements (2004-2010) of total aerosol number concentration and size distribution at Yonsei University located near the center of Seoul, South Korea. Total aerosol number concentration and cloud condensation nuclei number concentration at 0.6% supersaturation are in the range of 17838±6814 cm−3 and 5153±2636 cm−3. New particle formation (NPF) events were observed on 9.3% of the days. Here we present an interesting case of NPF event that occurred on a cloudy and rainy day. On this day, precursor gas (sulfur dioxide) concentration was lower than the monthly mean. However, aerosol concentration was low on this day due to precipitation. It seems that the low aerosol concentration due to precipitation crucially affected the NPF event. Comprehensive analysis will be made and presented at the conference.