Characteristics of aerosol optical properties and total amount of trace gases over Korea during the 2015 MAPS-Seoul campaign using AERONET and Pandora spectrometer

To investigate characteristics of air quality and enhance the performance of the air quality model prediction and satellite retrieval, Korea-US Air Quality (KORUS-AQ) campaign was conducted over Korea in May-June, 2016. As pre-campaign of the KORUS-AQ, Megacity Air Pollution Studies (MAPS)-Seoul campaign was held from May 18 to June 14, 2015. During this campaign, eight AErosol RObotic NETwork (AERONET) sunphotometers and six Pandora spectrometers observed the aerosol optical properties and total column density of O3 and NO2 over Korea, respectively. Using these data set, we examine the general spatiotemporal characteristic of aerosol optical properties and some trace gases in South Korea. Mean aerosol optical depth (AOD) at 550nm at Seoul (megacity region) and Gosan (coastal region) are 0.338 and 0.214 respectively during MAPS campaign, which are quite lower values compare to other recent years (2011 to 2014); The range of mean AOD in the same period is 0.557-0.684 at Seoul and 0.447-0.618 at Gosan. The reason of low AOD during MAPS period is not clearly understood yet. In this period, most of AERONET sites show the black carbon dominance except Gosan, showing a dominance of non-absorbing particles. This looks because the Gosan site is affected by the relatively clean maritime air-mass. Pandora O3 measurements have low spatial variability, but NO2 measurements shows larger spatiotemporal variability. Pandora total O3 vertical column density (VCD) shows a good agreement OMI O3 VCD (R > 0.9) probably due to low spatial variability of O3, In the contrast, Pandora total NO2 VCD does not much correlates with OMI NO2 VCDs. In addition to high variability of NO2, the influence of regional aerosol optical properties on the estimation of total NO2 VCD seems another reason to explain the poor relationship between Pandora and OMI NO2 VCD. To investigate the effect of aerosol optical properties on total NO2 VCD, AOD, single scattering albedo and fine mode fraction from AERONET observations are also compared to total NO2 VCD from Pandora and OMI measurements.