1. 스크린샷 2019-02-20 오전 10.58.37.png
    Title
    Impacts of local vs. trans-boundary emissions on PM2.5 exposure in South Korea
    Authors
    Jinkyul Choi, Rokjin J. Park, et al.
    Picture caption
    Figure shows spatial distributions of contributions from the five most important emission sources to population exposure to PM2.5 in South Korea during the KORUS-AQ: (b) anthropogenic NH3, (c) NOx, (d) SO2, (e) OC, and (f) BC.
    Summary
    High concentrations of PM2.5 have become a serious environmental issue in South Korea, which ranked 1st or 2nd among OECD countries in terms of population exposure to PM2.5. Quantitative understanding of PM2.5 source attribution is thus crucial for developing efficient air quality mitigation strategies. Here we use a suite of extensive observations ofPM2.5 and its precursors concentrations during the international KORea-US cooperative Air Quality field study in Korea (KORUS-AQ) in May–June 2016 to investigate source contributions to PM2.5 in South Korea under various meteorological conditions. For the quantitative analysis, we updated a 3-D chemical transport model, GEOS-Chem, and its adjoint with the latest regional emission inventory and other recent findings. The updated model is evaluated by comparing against observed daily PM2.5 and its component con- centrations from six ground sites (Bangnyung, Bulkwang, Olympic park, Gwangju, Ulsan, and Jeju). Overall, simulated concentrations of daily PM2.5 and its components are in a good agreement with observations over the peninsula. We conduct an adjoint sensitivity analysis for simulated surface level PM2.5 concentrations at five ground sites (except for Bangnyung because of its small population) under four different meteorological con- ditions: dynamic weather, stagnant, extreme pollution, and blocking periods. Source contributions by regions vary greatly depending on synoptic meteorological conditions. Chinese contribution accounts for almost 68% of PM2.5 in surface air in South Korea during the extreme pollution period of the campaign, whereas an enhanced contribution from domestic sources (57%) occurs for the blocking period. Results from our sensitivity analysis suggest that the reduction of domestic anthropogenic NH3 emissions could be most effective in reducing po- pulation exposure to PM2.5 in South Korea (effectiveness=14%) followed by anthropogenic SO2 emissions from Shandong region (effectiveness=11%), domestic anthropogenic NOx emissions (effectiveness=10%), anthropogenic NH3 emissions from Shandong region (effectiveness=8%), anthropogenic NOx emissions from Shandong region (effectiveness=7%), domestic anthropogenic OC emissions (effectiveness=7%), and do- mestic anthropogenic BC emissions (effectiveness=5%).
    1. airchem_AFCID.PNG
    Title
    Influence of the AFCID on winter air quality in East Asia
    Authors
    Jaein I. Jeong and Rokjin J. Park
    Picture caption
    Enhancements of (a) concentration [μg m-3], and (b) percentage [%] of surface PM10 due to AFCID in the winter. PM10 concentrations for (c) without, and (d) with AFCID emissions.
    Summary
    We estimate the effects of the anthropogenic fugitive, combustion, and industrial dust (AFCID) on winter air quality in China and South Korea for November 2015–March 2016 using the KU-CREATE monthly anthropogenic emission inventory in conjunction with a nested version of GEOS-Chem. We find that AFCID amounts to winter PM10 concentrations of 17.9 μg m-3 (17%) in eastern causing a significant impact on air quality to downwind regions. Including AFCID in the model results in an increase of simulated winter PM10 concentrations in South Korea by 3.1 μg m-3 (9%), of which transboundary transport from China accounts for more than 70% of this increased PM10 concentration. Our results indicate that AFCID is an essential factor for winter PM10 concentrations over East Asia and its sources and physical characteristics need to be better quantified to improve PM air quality forecasts.
    1. Screen Shot 2020-01-08 at 12.11.55 PM.png
    Title
    Description of the HCHO retrieval algorithm for GEMS
    Authors
    Kwon et al. (2019)
    Picture caption
    Flow chart for GEMS HCHO algorithm.
    Summary
    We describe a formaldehyde (HCHO) retrieval algorithm for the Geostationary Environment Monitoring Spectrometer (GEMS) that will be launched by the Korean Ministry of Environment in 2019. The algorithm comprises three steps: pre-processes, radiance fitting, and post-processes. The pre-processes include a wavelength calibration, and interpolation and convolution of absorption cross-sections; radiance fitting is conducted using a non-linear fitting method referred to as basic optical absorption spectroscopy (BOAS); and post-processes include air mass factor calculations and bias corrections. In this study, several sensitivity tests are conducted to examine the retrieval uncertainties using the GEMS HCHO algorithm. We evaluate the algorithm with the OMI Level 1B irradiance/radiance data by comparing our retrieved HCHO column densities with OMI HCHO products of the Smithsonian Astrophysical Observatory (OMHCHO) and of the Quality Assurance for Essential Climate Variables project (OMI QA4ECV). Results show that OMI HCHO slant columns retrieved using the GEMS algorithm are in good agreement with OMHCHO, with correlation coefficients of 0.77–0.91 and regression slopes of 0.94–1.04 for March, June, September, and December 2005. Spatial distributions of HCHO slant columns from the GEMS algorithm are consistent with the OMI QA4ECV products, but relatively poorer correlation coefficients of 0.52 to 0.76 are found compared to those against the OMHCHO products. Also, we compare the satellite results with ground-based MAX-DOAS observations. OMI GEMS HCHO vertical columns are by 9–25% lower than those of MAX-DOAS at Haute-Provence Observatory (OHP) in France, Bremen in Germany, and Xianghe in China. We find that the OMI GEMS retrievals have less bias than the OMHCHO and OMI QA4ECV products at OHP and Bremen in comparison with MAX-DOAS.
    1. 스크린샷 2020-01-08 오후 12.25.09.png
    Title
    Evaluation of simulated O3 production efficiency during the KORUS-AQ campaign
    Authors
    Yujin J. Oak, Rokjin J. Park, et al.
    Picture caption
    Spatial distributions of simulated OPE at surface level and responses to NOx and VOCs emission changes in South Korea.
    Summary
    We examine O3 production and its sensitivity to precursor gases and boundary layer mixing in Korea by using a 3-D global chemistry transport model and extensive observations during the KORea-US cooperative Air Qual- ity field study in Korea, which occurred in May–June 2016. During the campaign, observed aromatic species onboard the NASA DC-8 aircraft, especially toluene, showed high mixing ratios of up to 10 ppbv, emphasizing the importance of aromatic chemistry in O3 production. To examine the role of VOCs and NOx in O3 chemistry, we first implement a detailed aromatic chemistry scheme in the model, which reduces the normalized mean bias of simulated O3 mixing ratios from –26% to –13%. Aromatic chemistry also increases the average net O3 production in Korea by 37%. Corrections of daytime PBL heights, which are overestimated in the model compared to lidar observations, increase the net O3 production rate by ~10%. In addition, increasing NOx emissions by 50% in the model shows best performance in reproducing O3 production characteristics, which implies that NOx emissions are underestimated in the current emissions inventory. Sensitivity tests show that a 30% decrease in anthropogenic NOx emissions in Korea increases the O3 production efficiency throughout the country, making rural regions ~2 times more efficient in producing O3 per NOx consumed. Simulated O3 levels overall decrease in the peninsula except for urban and other industrial areas, with the largest increase (~6 ppbv) in the Seoul Metropolitan Area (SMA). However, with simultaneous reductions in both NOx and VOCs emissions by 30%, O3 decreases in most of the country, including the SMA. This implies the importance of concurrent emission reductions for both NOx and VOCs in order to effectively reduce O3 levels in Korea.
    1. SSA.png
    Title
    Parametric analysis for global single scattering albedo calculations
    Authors
    Jaein I. Jeong, Duseong S. Jo, Rokjin J. Park, Hyung-Min Lee, Gabriele Curci, Sang-Woo Kim
    Picture caption
    Scatterplots of the observed versus simulated monthly mean SSA at 440 nm
    Summary
    We investigate the sensitivity of SSA calculations to physical input parameters (e.g., mixing state, size distribution, density, and refractive index of aerosols) associated with absorbing aerosols (e.g., black carbon [BC], brown carbon [BrC], and soil dust). We attempted to estimate global aerosol SSAs using the 3-D global chemical transport model (GEOS-Chem) and a FlexAOD. Our sensitivity tests show that the physical input parameters, which are not as well understood as aerosol mass concentrations, can lead to large uncertainties in global SSA values. We find that BC mixing state, BrC, and a dust size distribution have significant impacts on the global SSA calculation. Their combined use can reduce aerosol SSA bias in the model by 43% at 440 nm, compared to observations. We also find that the direct radiative effect (DRE) of global aerosols increases by 10% (from -2.62 W m-2 to -2.36 W m-2) when the SSA bias is corrected.