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(1)Characteristics of Aerosol Size Distribution During Large-scale Transport of Air Pollution Over the Yellow Sea Region in 2008 1. Hak-Sung Kim1, Yong-Seung Chung2, and Sun-Gu Lee3. Korea Centre for Atmospheric Environment Research, Cheongwon, Choongbuk, Korea, envir007@chol.com Korea Centre for Atmospheric Environment Research, Cheongwon, Choongbuk, Korea, kccar1@kornet.net 3 Satellite Operations & Application Division, Satellite Information Research Institute (SIRI), Korea Aerospace Research Institute (KARI), Daejeon, Korea, leesg@kari.re.kr 2. ABSTRACT Episodes of large-scale transport of airborne dust and anthropogenic pollutant particles from different sources in the East Asian continent in 2008 were identified by National Oceanic and Atmospheric Administration (NOAA) satellite RGB-composite images and the mass concentrations of ground level particulate matters. These particles were divided into dust, sea salt, smoke plume, and sulphate by an aerosol classification algorithm. To analyze the aerosol size distribution during large-scale transport of atmospheric aerosols, aerosol optical depth (AOD; proportional to the aerosol total loading in a vertical column) and fine aerosol weighting (FW; fractional contribution of fine aerosol to the total AOD) of Moderate Imaging Spectro-radiometer (MODIS) aerosol products were used over the East Asian region. KEY WORDS: Dust particles, Anthropogenic pollutant particles, TSP, PM10, PM2.5, Satellite observation 1. INSTRUCTION. Atmospheric aerosols are known to affect the radiative budget, climate change, and global carbon, nitrogen, and sulfur cycles (IPCC, 2007). They affect the rainfall processes by interacting with cloud particles (Lohmann et al., 2007). Aerosols are atmospheric pollutant substances that reduce visibility and adversely affect human health when inhaled (Liu et al., 2009). As a rule, atmospheric aerosols fall into categories of coarse particles (≥ 2.5 ㎛) and fine particles ( < 2.5 ㎛) depending on their size. Mechanical pulverizing processes usually generate coarse particles over natural sources, such as dust and sea salt. However, anthropogenic sources emit mainly fine particles by the burning of fossil fuels and are produced in the processes of industrial activities. Numerous studies exploit aerosol optical observations retrieved by satellites given the spatial coverage provided by satellites (Chung and Le, 1984, Chung and Kim, 2008, Kim and Chung, 2008). The MODIS aerosol standard products over both ocean and land were analyzed to evaluate the spatial and temporal variability of atmospheric aerosols over the East Asian region (Xiao et al., 2009). AODs rise high over the Northeast China, Korean Peninsula, and Japan, and then significantly decrease as the air pollutants transport from the nearcontinent ocean to remote oceans (Lee et al., 2007). The distribution of FW indicates that atmospheric fine aerosols reach a high level over major urban and industrialized areas even though fine aerosols of natural as well as anthropogenic origin exist over both the land and ocean in East Asia (Lee et al., 2007). Recent studies have focused on the classification of aerosol types to demonstrate the evidence of pollution transport; that is, anthropogenic aerosol types are detected over the ocean. as well as over the land (Kaufman et al., 2005, Lee et al., 2007) . However, the sparse observations of particulate matters on the ground level during large-scale air pollution transport left the satellite data as only means without their validation. Furthermore, many previous studies used averaged satellite aerosol data in monthly climatology over the East Asian region. In this study, episodes of large-scale transport of sandstorms and anthropogenic pollutant particles originating from the East Asian continent were observed at Cheongwon in 2008. 2.. OBSERVATION AND DATA ANALYSIS. The NOAA satellite’s Advanced Very High Resolution Radiometer (AVHRR) is equipped with six channels. RGB-composite images are created using three channels, including 1, 2, and 4, from AVHRR data. The mass concentrations of TSP, PM10, and PM2.5 particulate matters were observed by using the TEOM Series 1400a by Rupprecht & Patashnic, which is designed to measure the mass of dust collected in a filter by means of the TEOM (Tapered Element Oscillating Microbalance) method. To examine the spatial distribution of the large-scale transport of aerosols in the Yellow Sea area, AOD (τ) at 0.55 ㎛ and FW (η) at 0.55 ㎛ were employed in the MOD04/MYD04_L2 of MODIS aerosol data. The aerosol types were also divided into four types, dust, sea salt, smoke plume, and sulphate, by using the algorithm suggested by Lee et al. (2007), wherein MODIS AOD, Angstrom exponent (å), and the aerosol index (AI) of the Ozone Monitoring Instrument (OMI) were used..

(2) 3. RESULTS AND DISSCUSSION 3.1 Mass concentrations of particulate matter at. Cheongwon during 2008 Figure 1 shows the daily maximum values and variations in the mass concentrations of TSP, PM10, and PM2.5 as measured at Cheongwon. Average mass concentrations of TSP, PM10, and PM2.5 stood at 61±44 μgm-3, 41±35 μgm-3, and 24±18 μgm-3, respectively, with PM10 and PM2.5 from total mass concentration TSP pointing to 67% and 39%, respectively. Atmospheric aerosols generated in Korea and transported (~ 100 km) to Cheongwon can affect the dayto-day variations of the TSP, PM10, and PM2.5 mass concentrations. However, the NOAA satellite’s RGBcomposite images have been analyzed for many episodes of large-scale transport of airborne particles traversing the Yellow Sea and moving over to the Korean Peninsula. When episodes of large-scale transport of airborne particles occurred at Cheongwon, TSP, PM10, and PM2.5 mass concentrations increased sharply and caused rapid changes in the ratios of PM10 and PM2.5 to TSP, depending on the source.. The hourly variations in the TSP, PM10, and PM2.5 mass concentrations were observed at Cheongwon during March 2~3, 2008 at ground level (Fig. 2(d)). The mass concentrations of TSP (193 ㎍ m-3) and PM10 (135 ㎍ m3 ) were the highest at Chewongwon at 17–18 LST on March 2. PM10 mass concentration increased to an alarming 1330 ㎍ m-3 at Gwangju, in the southern part of Korea, at 16 LST the same day, thus revealing widely differing levels of mass concentration by area. Cheongwon, while affected by the massive airborne dust particles, registered a high PM2.5 mass concentration (68 ㎍ m-3), with a ratio out of TSP of 23%, showing that PM10-PM2.5 ratios rose drastically.. (a). (b). Figure 1. Day-to-day variations of daily maximum TSP, PM10, and PM2.5 concentrations observed at Cheongwon in 2008 at ground level.. (c). 3.2 Episodes of large-scale atmospheric aerosol transport. Figures 2(a) and 2(b) show NOAA satellite RGBcomposite images and aerosols classified by thethe MODIS-OMI algorithm for March 2, 2008. The strong sandstorms that originated from the southern part of the Gobi Desert covered the Yellow Sea after traversing the loess plateau of China on March 1. Dust particles were transported across the Korean Peninsula on March 2, where the results of an aerosol classification show that dust type aerosols were also observed. While other aerosol types were not clearly distinguishable in the RGB-composite images, dust/smoke mixtures were detected over the East China Sea; these mixtures are attributable to the sources of pollution transported from eastern China. The MODIS aerosol retrievals of Fig. 2(c) show fewer fine particles in the dust particles (average FW ratio of ~0.4). These dust particles were first observed in the Yellow Sea. The massive airborne dust particles were found countrywide from the afternoon of March 2.. (d) Figure 2. (a) NOAA satellite RGB-composite image (1353 LST, 2 March 2008) showing a massive dust cloud (DC) and associated airborne dust particles, (b) aerosol classification on the MODIS-OMI algorithm (2 March 2008), (c) histograms of AOD and FW values (2 March 2008), and (d) hourly variations of TSP, PM10 and PM2.5 measured at Cheongwon during 2~3 March 2008. On January 6, 2008, a high pressure system located in western China was affecting Korea and Japan as well. The NOAA satellite RGB-composite image shows anthropogenic pollutant particles over the Yellow Sea region, originating from eastern China (Fig. 3(a)). Also, in central Korea, a wide area was enveloped by dense fog..

(3) Smoke and dust/smoke mixtures over the Yellow Sea, the Korean Peninsula, and the Korea east sea on the MODISOMI algorithm are shown in Fig. 3(b). Figure 3(c) shows high proportions of fine particles with an average FW of ~0.7 to the total AOD of ~0.5 over the Yellow Sea region. Therefore, the hourly variations in the mass concentrations of TSP, PM10, and PM2.5 observed at Cheongwon show increased levels on January 7 (Fig. 3(d)). The maximum mass concentrations of TSP, PM10, and PM2.5 were measured as 171 ㎍ m-3, 136 ㎍ m-3, and 126 ㎍ m-3, respectively. The PM2.5 ratio out of TSP in particular rose to as high as 74%, and the PM10-PM2.5 ratio fell.. (a). (b). (c). (d) Figure 3. (a) NOAA Satellite RGB-composite image (1322 LST, 7 January 2008) showing large-scale air pollution transport (LSAPT) headed for Korea, (b) aerosol classification on the MODIS-OMI algorithm (7 January 2008) (c) histograms of AOD and FW over the Yellow Sea (7 January 2008), and (d) hourly variations of TSP, PM10 and PM2.5 observed at Cheogwon during 5~8 January 2008. Therefore, the proportion of PM10 and PM2.5 among the total mass concentration of TSP in the large-scale transport of atmospheric aerosols originating from different sources had many differences. Six episodes of airborne dust particles and five cases of anthropogenic pollutant particles were observed at Cheongwon in 2008. The hourly maximum values of TSP, PM10, and PM2.5 concentrations are summarized in Table 1. The proportions of the daily highs of PM10 and PM2.5. among the total mass concentration for the six airborne dust particle episodes stood at 70% and 16%, respectively, in 2008; those of anthropogenic pollutant particles stood at 82% and 65%, respectively. The increase of anthropogenic pollutant particles at the downwind site resulted in a high proportion of fine aerosols, while the ratios of PM10-PM2.5 declined.. 3.3 Analysis of AOD and FW distributions in the. East Asian region Figures 4(a) and 4(b) show the data of AOD, FW, and aerosol classification for episodes of massive airborne dust particles and anthropogenic pollutant particles in 2008, as summarized in Table 1. AOD and FW values were averaged over the period during which expansive sandstorms and anthropogenic pollutant particles drifted into the central part of the Korean Peninsula. Both AOD and FW figures of 0.2 or lower are left colour-less. The average AOD of airborne dust particles and anthropogenic pollutant particles stood at 0.36±0.13 and 0.42±0.17, respectively, showing that anthropogenic pollutant particles contribute more to AOD on a large-scale. The anthropogenic pollutant particles, largely smoke by type, noticeably affected eastern China, the Yellow Sea, the Korean Peninsula, and the Korea east sea. In contrast, AOD values decreased over areas of the North Pacific Ocean at latitudes lower than Japan. The AOD in the case of sandstorms occurring and transported also shows high levels in areas such as the Shantung Peninsula of China, the Yellow Sea, and the Korea east sea on an expansive scale. The dust aerosol distribution obtained from the MODIS-OMI algorithm in the same area is comparable with that of the MODIS AOD. On average, AOD values of massive airborne dust particles, smoke, and dust/smoke mixtures by aerosol classification are partly responsible for the high levels of AOD figures in such places as eastern coastal areas below the Shantung Peninsula. FW values for massive airborne dust particles and anthropogenic pollutant particles stood at 0.52±0.13 and 0.63±0.16, respectively. The FWs were averaged for a wide area where the occurrence and transport of duststorms and anthropogenic air pollution were all documented, thus accounting for low levels. The fractional contributions of fine particles to AOD for expansive anthropogenic pollutant particles were higher than in the case of massive airborne dust particles. FW values for anthropogenic pollutant particles dispersed on a large-scale over the Yellow Sea and the Korea east sea, as well as eastern China and the NE portion of the Korean Peninsula, are shown to run high. Also, FW values run high in Korea and Japan. However, very low FW values are shown in northern China and Mongolia, which are the sources of the sandstorms..

(4) average of 0.63±0.16 in the case of anthropogenic pollutant particles, a value higher than that (0.52±0.13) in the case of sandstorms, thus pointing to the higher contribution of anthropogenic fine pollutant particles to atmospheric aerosols in the Yellow Sea region. However, FW values were very low at sandstorm sources, including northern China and Mongolia. 5. REFERENCES. (a). (b) Figure 4. Average AOD (upper), FW (middle), and aerosol classification (lower) based on the data of MODIS level 2 and MODIS-OMI algorithm caused by episodes of (a) dust particles and (b) anthropogenic pollutant particles in 2008. 4. CONCLUSIONS Six episodes of airborne dust particles showed PM10 and PM2.5 ratios out of TSP of 70% and 16%, respectively, reflecting a low PM2.5 ratio. The fine aerosol ratio was low and the ratio of coarse particles of PM10-PM2.5 rose due to airborne dust particles. These particles were generated by physical processes at natural sources. The five episodes in which expansive transport of polluted particles originating from industrial areas in eastern China flowed into the Korean Peninsula showed PM10 and PM2.5 ratios out of TSP of 82% and 65%, respectively. The episodes of anthropogenic pollutant particles, clearly distinguishable from aerosol type airborne dust particles, show that smoke covered a wide area ranging from eastern China all the way to the Yellow Sea, the Korean Peninsula, and the Korea east sea. Average AOD for episodes of anthropogenic pollutant particles stood at 0.42±0.17, showing that pollutant particles noticeably affected atmospheric aerosols, compared with AOD (0.36±0.13) caused by sandstorms. FW values also registered an. Chung, Y.S. and Kim, H.S., 2008, Observations of massive-air pollution transport and associated air quality in the Yellow Sea region. International Journal Air Quality, Atmosphere and Health, 1, pp. 69-70. Chung, Y.S., and Le, H.V., 1984, Detection of forest-fire smoke plumes by satellite image. Atmospheric Environment, 18, pp. 2143–2151. IPCC, 2007, Climate Change 2007: The Physical Science Basis. Working group I contribution to the fourth assessment report of the intergovernmental panel on climate change, Summary for Policymakers, Cambridge University Press, Cambridge, UK, 996 pp. Kaufman, Y.J., Boucher, O., Tanre, D., Chin, M., Remer, L.A. and Takemura, T., 2005, Aerosol anthropogenic component estimated from satellite data. Geophysical Research Letters, 32, L17804, doi:10.1029/2005 GL023125. Kim, H.S. and Chung, Y.S., 2008, Satellite and ground observations for large-scale air pollution transport in the Yellow Sea Region. Journal of Atmospheric Chemistry, 60, pp. 103-116. Lee, J.H., Kim, J.H., Lee, H.C. and Takemura, T., 2007, Classification of aerosol type from MODIS and OMI over East Asia. Journal of the Korean Meteorological Society, 43, pp. 343-357. Liu, J., Mauzerall, D. and Horowitz, L.W., 2009, Evaluating inter-continental transport of fine aerosols:(2) Global health impact. Atmospheric Environment, 43, pp. 4339-4347. Lohmann, U., Stier, P., Hoose, C., Ferrachat, S., Kloster, S., Roeckner, E. and Zhang J., 2007, Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM, Atmospheric Chemistry and Physics, 7, pp. 3425–3446. Xiao, N., Shi, T., Calder, C.A., Munroe, D.K., Berrett, C., Wolfinbarger, S. and Li, D., 2009, Spatial characteristics of the difference between MISR and MODIS aerosol optical depth retrievals over mainland southeast Asia. Remote Sensing of Environment, 113, pp. 1-9. 6. ACKNOWLEDGEMENTS Research funding from the CATER(2006-3103) contributed to this work. We are also grateful to M. H. Lee in KCAER..

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