Browsing by Author "Kang, CH"
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- ItemAnalysis of a decade of Asian outflow of PM10 and TSP to Gosan, Korea: also incorporating Radon-222(Elsevier B.V., 2015-05) Crawford, J; Chambers, SD; Kang, CH; Griffiths, AD; Kim, WHTen years of aerosol and Radon–222 (radon) data from Gosan, Korea, were analyzed. Seasonal cycles were strongly linked to changes in fetch and time of year. We estimated that 7.21 t/m y of PMio aerosol pass Gosan in the atmospheric boundary layer, increasing annually by 0.3 t/m y. Contributions to aerosol loading were characterized by fetch: South China, North China, Korea and Japan. While the highest, and most variable, contributions typically originated from South China, these air masses contributed to only 6% of the overall dataset. PM10 distributions were broader from South and North China than for Korea or Japan, reflecting differences in natural/anthropogenic soil sources, and number/distribution of large point sources. Employing radon to select air masses more representative of targeted fetch regions typically resulted in greater reported pollutant concentrations and rates of change over the decade. Estimated rates of PM10 increase from North China and Korea over the decade were 1.4 and 0.9 μg/m3 y, respectively. Total suspended particulate (TSP) elemental analysis indicated that the (non–sea–salt) nss–SO42− content of aerosols has been gradually increasing over the past decade and more recently an increase in NO3− was seen. However, on average, rates of increase in nss–SO42− have reduced since 2007, which were higher in South than North China. © 2020 Elsevier B.V.
- ItemBackground level of atmospheric radon-222 concentrations at Gosan Station, Jeju Island, Korea in 2011(Korea Science, 2014-04-20) Kim, WH; Ko, HJ; Hu, CG; Lee, HY; Lee, CK; Chambers, SD; Williams, AG; Kang, CHReal-time monitoring of hourly atmospheric radon (Rn-222) concentration was performed throughout 2011 at Gosan station, Jeju Island, one of the least polluted regions in Korea, in order to characterize the background levels, and temporal variations on diurnal to seasonal time-scales. The annual mean radon concentration for 2011 was mBq , and the seasonal cycle was characterized by a broad winter maximum, and narrow summer minimum. Mean monthly radon concentrations, in descending order of magnitude, were Oct > Sep > Feb > Nov > Jan > Dec > Mar > Aug > Apr > Jun > May > Jul. The maximum monthly mean value (3595 mBq , October), exceeded the minimum value (1243 mBq , July), by almost a factor of three. Diurnal composite hourly concentrations increased throughout the night to reach their maximum (2956 mBq ) at around 7 a.m., after which they decreased to their minimum value (2259 mBq ) at around 3 p.m. Back trajectory analyses indicated that the highest radon events typically exhibited long-term continental fetch over Asia before arriving at Jeju. In contrast, low radon events were generally correlated with air mass fetch over the North Pacific Ocean. Radon concentrations typical of predominantly continental, and predominantly oceanic fetch, differed by a factor of 3.8. (C) KISTI. All Rights Reserved.
- ItemConcentration variability of atmospheric radon and gaseous pollutants at background area of Korea between 2017 and 2018(Korea Institute of Science and Technology Information, 2022-02-25) Kim, WH; Yang, HS; Bu, JO; Kang, CH; Song, JM; Chambers, SDThe concentrations of radon in the atmosphere were measured at the Gosan site of Jeju Island during 2017-2018, in order to investigate the time-series variation characteristics and the dependency of airflow transport pathways. The mean 222Rn concentration was 2,480 mBq m-3, and its monthly concentration in November was 3,262 mBq m-3, more than twice as that in July (1,459 mBq m-3). The diurnal radon concentrations increased throughout the nighttime to the maximum (2,862 mBq m-3) at around 7 a.m., then gradually decreased throughout the daytime by the minimum (1,997 mBq m-3) at around 3 p.m. The seasonal and monthly variations of CO, NO2, O3 showed a roughly similar pattern to that of radon for the same period, as high in winter and low in summer. The cluster back trajectory analysis described that about 60 % of overall airflow pathways was influenced by the airflow from China. The concentrations of radon and gaseous pollutants were relatively high as the airflow was influenced by China continent, but comparatively much lower as influenced by the northern Pacific Ocean. © The Authors - open access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licence.
- ItemEvaluate transport processes in MERRA driven chemical transport models using updated 222Rn emission inventories and global observations(AGU, 2015-12-14) Zhang, B; Liu, HY; Crawford, J; Fairlie, TD; Chen, G; Chambers, SD; Kang, CH; Williams, AG; Zhang, K; Considine, DB; Sulprizio, MP; Yantosca, RMConvective and synoptic processes play a major role in determining the transport and distribution of trace gases and aerosols in the troposphere. The representation of these processes in global models (at ~100-1000 km horizontal resolution) is challenging, because convection is a sub-grid process and needs to be parameterized, while synoptic processes are close to the grid scale. Depending on the parameterization schemes used in climate models, the role of convection in transporting trace gases and aerosols may vary from model to model. 222Rn is a chemically inert and radioactive gas constantly emitted from soil and has a half-life (3.8 days) comparable to synoptic timescale, which makes it an effective tracer for convective and synoptic transport. In this study, we evaluate the convective and synoptic transport in two chemical transport models (GMI and GEOS-Chem), both driven by the NASA’s MERRA reanalysis. Considering the uncertainties in 222Rn emissions, we incorporate two more recent scenarios with regionally varying 222Rn emissions into GEOS-Chem/MERRA and compare the simulation results with those using the relatively uniform 222Rn emissions in the standard model. We evaluate the global distribution and seasonality of 222Rn concentrations simulated by the two models against an extended collection of 222Rn observations from 1970s to 2010s. The intercomparison will improve our understanding of the spatial variability in global 222Rn emissions, including the suspected excessive 222Rn emissions in East Asia, and provide useful feedbacks on 222Rn emission models. We will assess 222Rn vertical distributions at different latitudes in the models using observations at surface sites and in the upper troposphere and lower stratosphere. Results will be compared with previous models driven by other meteorological fields (e.g., fvGCM and GEOS4). Since the decay of 222Rn is the source of 210Pb, a useful radionuclide tracer attached to submicron aerosols, improved understanding of emissions and transport of 222Rn will provide insights into the transport, distribution, and wet deposition of 210Pb aerosols.
- ItemImproving estimates of pollution outflow at Gosan using 222Rn(World Meteorological Organization, 2015-11-01) Chambers, SD; Kang, CH; Williams, AG; Crawford, J; Griffiths, AD; Kim, WHThe best understanding of climatic, ecological and health effects from increasing Southeast Asian emissions will likely be achieved by models coupled to detailed emission inventories and remote sensing data. To improve model accuracy and forecast horizons, careful evaluation against appropriate observations is essential. To minimize the chance of misleading comparisons, it is important to ensure ground-based reference observations are well matched with the model output, especially regarding fetch regions and scales of observation. To quantify upstream emissions based on ground-based observations it is necessary to: (i) understand the measurement “footprint”, (ii) identify observations most representative of air that has been in good contact with the surface over which it has travelled, and has not been significantly diluted by fronts or deep convection in transit, (iii) ensure observations are representative of the whole boundary layer (BL), (iv) minimize the influence of local emissions, (v) characterize changes in mixing depth, and (vi) characterize evolving “background” concentrations.
- ItemImproving the representation of cross-boundary transport of anthropogenic pollution in East Asia using radon-222(Taiwan Association for Aerosol Research, 2016-01-01) Chambers, SD; Kang, CH; Williams, AG; Crawford, J; Griffiths, AD; Kim, KH; Kim, WHWe report on 10 years of hourly atmospheric radon, CO, and SO2 observations at Gosan Station, Korea. An improved radon detector was installed during this period and performance of the detectors is compared. A technique is developed whereby the distribution of radon concentrations from a fetch region can be used to select air masses that have consistently been in direct contact with land-based emissions, and have been least diluted en route to the measurement site. Hourly radon concentrations are used to demonstrate and characterise contamination of remote-fetch pollution observations by local emissions at this key WMO GAW site, and a seasonally-varying 5-hour diurnal sampling window is proposed for days on which diurnal cycles are evident to minimise these effects. The seasonal variability in mixing depth and “background” pollutant concentrations are characterised. Based on a subset of observations most representative of the important regional fetch areas for this site, and least affected by local emissions, seasonal estimates of CO and SO2 in air masses originating from South China, North China, Korea and Japan are compared across the decade of observations. 2016, © Taiwan Association for Aerosol Research
- ItemInfluence of turbulent mixing and air circulation in the lower atmosphere on fetch areas of selected WMO Global Atmosphere Watch baseline air pollution stations.(World Meteorological Organization, 2008-06-09) Zahorowski, W; Chambers, SD; Kang, CH; Crawford, J; Werczynski, S; Williams, AGThe World Meteorological Organisation (WMO) established the Global Atmosphere Watch (GAW) Programme in 1989. The scientific goals of GAW relate to investigating the role of atmospheric chemistry in global climate change, and include: understanding the complex mechanisms with respect to natural and anthropogenic atmospheric change; and improving the understanding of interactions between the atmosphere, ocean, and biosphere.
- ItemSimulation of radon-222 with the GEOS-Chem global model: emissions, seasonality, and convective transport(Copernicus Publications, 2021-02-10) Zhang, B; Liu, HY; Crawford, JH; Chen, G; Fairlie, TD; Chambers, SD; Kang, CH; Williams, AG; Zhang, K; Considine, DB; Sulprizio, MP; Yantosca, RMRadon-222 (222Rn) is a short-lived radioactive gas naturally emitted from land surfaces and has long been used to assess convective transport in atmospheric models. In this study, we simulate 222Rn using the GEOS-Chem chemical transport model to improve our understanding of 222Rn emissions and surface concentration seasonality and characterize convective transport associated with two Goddard Earth Observing System (GEOS) meteorological products, the Modern-Era Retrospective analysis for Research and Applications (MERRA) and GEOS Forward Processing (GEOS-FP). We evaluate four global 222Rn emission scenarios by comparing model results with observations at 51 surface sites. The default emission scenario in GEOS-Chem yields a moderate agreement with surface observations globally (68.9 % of data within a factor of 2) and a large underestimate of winter surface 222Rn concentrations at Northern Hemisphere midlatitudes and high latitudes due to an oversimplified formulation of 222Rn emission fluxes (1 atom cm−2 s−1 over land with a reduction by a factor of 3 under freezing conditions). We compose a new global 222Rn emission scenario based on Zhang et al. (2011) and demonstrate its potential to improve simulated surface 222Rn concentrations and seasonality. The regional components of this scenario include spatially and temporally varying emission fluxes derived from previous measurements of soil radium content and soil exhalation models, which are key factors in determining 222Rn emission flux rates. However, large model underestimates of surface 222Rn concentrations still exist in Asia, suggesting unusually high regional 222Rn emissions. We therefore propose a conservative upscaling factor of 1.2 for 222Rn emission fluxes in China, which was also constrained by observed deposition fluxes of 210Pb (a progeny of 222Rn). With this modification, the model shows better agreement with observations in Europe and North America (> 80 % of data within a factor of 2) and reasonable agreement in Asia (close to 70 %). Further constraints on 222Rn emissions would require additional concentration and emission flux observations in the central United States, Canada, Africa, and Asia. We also compare and assess convective transport in model simulations driven by MERRA and GEOS-FP using observed 222Rn vertical profiles in northern midlatitude summer and from three short-term airborne campaigns. While simulations with both GEOS products are able to capture the observed vertical gradient of 222Rn concentrations in the lower troposphere (0–4 km), neither correctly represents the level of convective detrainment, resulting in biases in the middle and upper troposphere. Compared with GEOS-FP, MERRA leads to stronger convective transport of 222Rn, which is partially compensated for by its weaker large-scale vertical advection, resulting in similar global vertical distributions of 222Rn concentrations between the two simulations. This has important implications for using chemical transport models to interpret the transport of other trace species when these GEOS products are used as driving meteorology. © Author(s) 2021.
- ItemThe use of radon in the analysis of a decade of Asian outflow of PM10 and TSP to Gosan, Korea(University of New South Wales and Australian Nuclear Science and Technology Organisation, 2015-07-10) Crawford, J; Chambers, SD; Kang, CH; Griffiths, AD; Kim, WHNot provided to ANSTO Library.