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Despite the significant progress in improving chemical transport models (CTMs), applications of these modeling endeavors are still subject to large and complex model uncertainty. The Model Inter-Comparison Study for Asia III (MICS-Asia III) has provided the opportunity to assess the capability and uncertainty of current CTMs in East Asian applications. In this study, we have evaluated the multi-model simulations of nitrogen dioxide (NO2), carbon monoxide (CO) and ammonia (NH3) over China under the framework of MICS-Asia III. A total of 13 modeling results, provided by several independent groups from different countries and regions, were used in this study. Most of these models used the same modeling domain with a horizontal resolution of 45 km and were driven by common emission inventories and meteorological inputs. New observations over the North China Plain (NCP) and Pearl River Delta (PRD) regions were also available in MICS-Asia III, allowing the model evaluations over highly industrialized regions. The evaluation results show that most models captured the monthly and spatial patterns of NO2 concentrations in the NCP region well, though NO2 levels were slightly underestimated. Relatively poor performance in NO2 simulations was found in the PRD region, with larger root-mean-square error and lower spatial correlation coefficients, which may be related to the coarse resolution or inappropriate spatial allocations of the emission inventories in the PRD region. All models significantly underpredicted CO concentrations in both the NCP and PRD regions, with annual mean concentrations that were 65.4 % and 61.4 % underestimated by the ensemble mean. Such large underestimations suggest that CO emissions might be underestimated in the current emission inventory. In contrast to the good skills for simulating the monthly variations in NO2 and CO concentrations, all models failed to reproduce the observed monthly variations in NH3 concentrations in the NCP region. Most models mismatched the observed peak in July and showed negative correlation coefficients with the observations, which may be closely related to the uncertainty in the monthly variations in NH3 emissions and the NH3 gas–aerosol partitioning. Finally, model intercomparisons have been conducted to quantify the impacts of model uncertainty on the simulations of these gases, which are shown to increase with the reactivity of species. Models contained more uncertainty in the NH3 simulations. This suggests that for some highly active and/or short-lived primary pollutants, like NH3 , model uncertainty can also take a great part in the forecast uncertainty in addition to the emission uncertainty. Based on these results, some recommendations are made for future studies. [ABSTRACT FROM AUTHOR]

Spatiotemporal variations of ozone (O3) and nitrogen oxide (NOx) mixing ratios from 14 state-of-the-art chemical transport models (CTMs) are intercompared and evaluated with O3 observations in East Asia, within the framework of the Model Inter-Comparison Study for Asia Phase III (MICS-Asia III). This study was designed to evaluate the capabilities and uncertainties of current CTMs simulations for Asia and to provide multi-model estimates of pollutant distributions. These models were run by 14 independent groups working in China, Japan, South Korea, the United States and other countries/regions. Compared with the previous phase of MICS-Asia (MICS-Asia II), the evaluation with observations was extended from 4 months to 1 full year across China and the western Pacific Rim. In general, model performance levels for O3 varied widely by region and season. Most models captured the key patterns of monthly and diurnal variation of surface O3 and its precursors in the North China Plain and western Pacific Rim but failed to do so for the Pearl River Delta. A significant overestimation of surface O3 was evident from May to September/October and from January to May over the North China Plain, the western Pacific Rim and the Pearl River Delta. Comparisons drawn from observations show that the considerable diversity in O3 photochemical production partly contributed to this overestimation and to high levels of inter-model variability in O3 for North China. In terms of O3 soundings, the ensemble average of models reproduced the vertical structure for the western Pacific, but overestimated O3 levels to below 800 hPa in the summer. In the industrialized Pearl River Delta, the ensemble average presented an overestimation for the lower troposphere and an underestimation for the middle troposphere. The ensemble average of 13 models for O3 did not always exhibit superior performance compared with certain individual models in contrast with its superior value for Europe. This finding suggests that the spread of ensemble-model values does not represent all of the uncertainties of O3 or that most MICS-Asia III models missed key processes. This study improved the performance of modeling O3 in March at Japanese sites compared with MICS-Asia II. However, it overpredicted surface O3 concentrations for western Japan in July, which was not found by MICS-Asia II. Major challenges still remain with regard to identifying the sources of bias in surface O3 over East Asia in CTMs. [ABSTRACT FROM AUTHOR]

Kim C.-H.; Jang C. J., and Kim M.-W., 2018. A Numerical Simulation of Long-Term Sea Level Change in the East Asian Marginal Seas. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 546–550. Coconut Creek (Florida), ISSN 0749-0208. To investigate the regional sea level rise (SLR) and its possible mechanisms in the East Asian Marginal Seas (Yellow Sea (YS), East China Sea (ECS) and Japan/East Sea (JES)) sea level variation was simulated using the global ocean-sea ice coupled model (GFDL MOM5-SIS) forced with European Centre for Medium-range Weather Forecasts reanalysis data for 58 years (1958–2015). Seasonal variation in the simulated sea level shows comparable amplitude and phase to those of the satellite altimetry for 1993–2014 in each sea region. Rates of the simulated SLR are compared with those of the reconstructed sea level (Hamlington et al., 2011) and satellite altimetry sea level: rates of SLR in the YS, ECS and JES for 1958–2009 are 2.1 mm/yr, 2.6 mm/yr, 2.1 mm/yr in the model, and 2.2 mm/yr, 1.9 mm/yr, 2.2 mm/yr in the reconstructed sea level, respectively. For 1993–2014, the SLR rates in the YS, ECS and JES are 3.8 mm/yr, 4.1 mm/yr, 2.8 mm/yr in the model, and 3.4 mm/yr, 2.6 mm/yr, 3.1 mm/yr in the satellite altimetry sea level, respectively. The regional mean sea level distribution in the model shows the SLR of 2~5 cm for 2005 to 2014 relative to the period of 1993 to 2002, which is also evident in the satellite altimetry sea level but in more localized areas. In the SLR between those two periods, model simulation reveals that non-steric sea level change was dominant in the YS, ECS and JES, which is different from the Kuroshio region where steric component was dominant. This result suggests that the recent SLR in the East Asian Marginal Seas is mainly driven by the mass convergence such as the transport changes in the shelf area. [ABSTRACT FROM AUTHOR]

Jang, C.J.; Choi, W.; Shin, H.-J., and Kim C.-H., 2018. Future changes in the sea surface wind over the East Asian marginal seas projected by regional climate models. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 591–595. Coconut Creek (Florida), ISSN 0749-0208. Sea surface wind plays a crucial role in coastal safety including flooding and coastal erosion mainly by changing sea level and ocean wind waves, and the regional characteristics of sea surface wind can be influenced by global warming. This study aims to investigate future changes in sea surface wind due to global warming in the East Asian marginal seas (EAMS) projected by four different regional climate models contributing to CORDEX-EA (COordinated Regional climate Downscaling Experiment-East Asia) downscaling project, by using daily mean winds for the present (historical runs for 1980–2004) and the future climate (RCP4.5 scenario run for 2025–2049). In general, the climatological-mean wind speed is projected to decrease up to 30 % in winter, but to increase up to 40 % in summer, indicating seasonally different large-scale atmospheric responses to global warming in EAMS. The prevailing wind direction, a critical factor in coastal erosion in EAMS, is projected to be significantly changed in both winter and summer, contributing to the changes in the mean wind speed. Extreme winds, defined as an annual maximum of the wind speed, show negligible changes with considerably large intermodel differences. Our findings suggest that projected future changes in sea surface wind over EAMS can be considerably different depending on seasons and models. [ABSTRACT FROM AUTHOR]

Urban photochemical ozone (O3) formation regimes (NOx- and VOC-limited regimes) at nine megacities in East Asia were diagnosed based on near-surface O3 columns from 900 to 700 hPa, nitrogen dioxide (NO2), and formaldehyde (HCHO), which were inferred from measurements by ozone-monitoring instruments (OMI) for 2014–2018. The nine megacities included Beijing, Tianjin, Hebei, Shandong, Shanghai, Seoul, Busan, Tokyo, and Osaka. The space-borne HCHO–to–NO2 ratio (FNR) inferred from the OMI was applied to nine megacities and verified by a series of sensitivity tests of Weather Research and Forecasting model with Chemistry (WRF-Chem) simulations by halving the NOx and VOC emissions. The results showed that the satellite-based FNRs ranged from 1.20 to 2.62 and the regimes over the nine megacities were identified as almost NOx-saturated conditions, while the domain-averaged FNR in East Asia was >2. The results of WRF–Chem sensitivity modeling show that O3 increased when the NOx emissions reduced, whereas VOC emission reduction showed a significant decrease in O3, confirming the characteristics of VOC-limited conditions in all of the nine megacities. When both NOx and VOC emissions were reduced, O3 decreased in most cities, but increased in the three lowest-FNRs megacities, such as Shanghai, Seoul, and Tokyo, where weakened O3 titration caused by NOx reduction had a larger enough effect to offset O3 suppression induced by the decrease in VOCs. Our model results, therefore, indicated that the immediate VOC emission reduction is a key controlling factor to decrease megacity O3 in East Asia, and also suggested that both VOC and NOx reductions may not be of broad utility in O3 abatement in megacities and should be considered judiciously in highly NOx-saturated cities in East Asia. [ABSTRACT FROM AUTHOR]

Space-borne ozone (O3) measurements have indicated consistent positive trends across the entire Asia–Pacific region despite the considerable reduction of NOx since 2000s. The rate of increase in O3 derived from lower free tropospheric column measurements was observed to be 0.21 ± 0.05 DU/decade during 2005–2018. Our space-borne-based diagnosis of the nonlinear photochemical formation regimes, NOx-limited and NOx-saturated, show that O3 chemistry is undergoing a transitional process to the NOx-limited regime throughout most of the Asian region. Nevertheless, NOx-saturated conditions persist at present in and over eight major megacities. These NOx-saturated conditions in megacities contribute to the increased O3 due to NOx reduction, which could also affect the enhanced O3 concentrations throughout the Asia–Pacific region via long-range transport. This indicates that VOC limits along with NOx reductions are needed in megacities in the short term to reduce O3 levels. Moreover, NOx saturation in major megacities will continue until 2025, according to the forecast emission scenarios from the Intergovernmental Panel on Climate Change (IPCC). These scenarios gradually shift nearly all cities to the NOx-limited regime by 2050 with the exception of few cities under IPCC RCP8.5. Thus, continued reductions in NOx will be a key factor in reducing O3 in the long term. [ABSTRACT FROM AUTHOR]

High levels of atmospheric concentration of PM2.5 (particulate matters less than 2.5 μm in size) are one of the most urgent societal issues over the East Asian countries. Air quality models have been used as an essential tool to predict spatial and temporal distribution of the PM2.5 and to support relevant policy making. This study aims to investigate the performance of high-fidelity air quality models in simulating surface PM2.5 chemical composition over the East Asia region in terms of a prediction consistency, which is a prerequisite for accurate air quality forecasts and reliable policy decision. The WRF-Chem (Weather Research and Forecasting-Chemistry) and WRF/CMAQ (Weather Research and Forecasting/Community Multiscale Air Quality modeling system) models were selected and uniquely configured for a one-month simulation by controlling surface emissions and meteorological processes (model options) to investigate the prediction consistency focusing the analyses on the effects of meteorological and chemical processes. The results showed that the surface PM2.5 chemical components simulated by both the models had significant inconsistencies over East Asia ranging fractional differences of 53% ± 30% despite the differences in emissions and meteorological fields were minimal. The models' large inconsistencies in the surface PM2.5 concentration were attributed to the significant differences in each model's chemical responses to the meteorological variables, which were identified from the multiple linear regression analyses. Our findings suggest that the significant models' prediction inconsistencies should be considered with a great caution in the PM2.5 forecasts and policy support over the East Asian region. [ABSTRACT FROM AUTHOR]

This study analyzed the impact of shipping emissions on ozone (O 3) concentrations in East Asia during the Korea-United States Air Quality (KORUS-AQ) and the Satellite Integrated Joint monitoring for Air Quality (SIJAQ) 2021 campaign period. Numerical simulations were performed during the KORUS-AQ (May 2016, the KORUS case) and the SIJAQ 2021 (October–November 2021, the SIJAQ case) using Community Multi-scale Air Quality (CMAQ), the three-dimensional chemical transport model. We additionally simulated an experiment without shipping emissions to compare the impact with and without shipping emissions. Using the validated simulation results, the average O 3 concentrations in inland regions were found to be 35.63 ppb and 20.62 ppb in the KORUS and SIJAQ cases, respectively. The average O 3 concentrations were higher in the KORUS case owing to the difference in weather conditions between the two cases in various seasons. The results of examining the impact of shipping emissions on O 3 concentrations in the ocean area indicate that both the KORUS and SIJAQ cases resulted in a decrease in O 3 concentrations in the Yellow Sea region, while the O 3 concentrations increased in the East Sea and North Pacific regions. In particular, in the Yellow Sea and East China Sea, where the O 3 concentrations decreased in the KORUS case, O 3 sensitivity results showed volatile organic compounds (VOC)-sensitive regime when the shipping emissions were removed but changed to nitrogen oxide (NO x)-sensitive regime when the shipping emissions were added. Meanwhile, in the inland regions, the SIJAQ case decreased O 3 concentrations in most areas, whereas the KORUS case showed an increase in O 3 concentrations in the Korean Peninsula and Japan. Analysis of O 3 sensitivity revealed that the regions of the Korean Peninsula and Japan, where O 3 concentrations increased, exhibited a NO x -sensitive regime. Particularly, in the case of the Korean Peninsula, the initial transport of shipping emissions in the western part led to a decrease in O 3 concentrations. However, as shipping emissions were further transported from west to east, they became more diluted, and additional NO x generated by O 3 titration reactions was also transported, gradually increasing O 3 concentrations. Furthermore, we found that during seasons with abundant BVOC emissions, the transport of shipping emissions could contribute to additional O 3 production. These results confirmed that shipping emissions in East Asia primarily reduce O 3 concentrations, however, differences in seasonal and regional O 3 sensitivity and transportation patterns can contribute to O 3 production. [Display omitted] • O 3 concentration changes in the East Asian regions due to ocean emissions during the KORUS-AQ and SIJAQ campaign periods are investigated. • The influence of ocean emissions on the production and loss of O 3 varies by region and season. • The ocean emissions could result in the transition of the O 3 sensitivity regime in some ocean areas. • The seasonal transport of ocean emissions to BVOC-rich inland regions can contribute to the increase in O 3 concentration. [ABSTRACT FROM AUTHOR]

Severe haze episodes have occurred frequently throughout megacities in East Asia, especially during winter and early spring. Although notable progress has been attained in understanding the causes of severe haze formation, the exacerbation of PM 2.5 concentration due to Asian dust has not yet been fully investigated. Here, we investigated the contribution of weak Asian dust particles to PM 2.5 concentration during early spring for an extraordinarily long-lasting high PM 2.5 episode in Seoul, Korea. PM 2.5 concentrations exceeding national criteria (35 μg m−3) were continuously observed from February 27 to March 7, 2019, and can be attributable to the transboundary transported aerosols for the Asian continent under slow eastward-migrating anticyclones. The high-frequency of PM 10-2.5 and PM 2.5 mass concentrations in the high concentration regime (PM 10-2.5 > 30 μg m−3; PM 2.5 > 80 μg m−3) suggests that Asian dust particles transported concurrently with anthropogenic pollution aerosols contributed to elevated PM 2.5 concentration during this episode. This was also evident from an elevated depolarization ratio (δ 532 : 0.06–0.13) and aerosol volume concentrations both in coarse and fine modes, which indicates the presence of non-spherical dust particles, from collocated aerosol lidar and optical particle counter measurements. Unlike severe Asian dust episodes (PM 10 > 800 μg m−3) in Korea, relatively low Asian dust particle concentrations during high PM 2.5 haze episodes have not been accurately predicted and alerted by most air quality forecasting models. This study emphasizes the need for the implementation of a series of dust emission and transport processes for better predictions of PM 2.5 concentration during winter-spring high PM 2.5 episodes. [Display omitted] • Extraordinarily long-lasting high PM 2.5 episode was studied. • Asian dust particles transported contributed to elevated PM 2.5 concentration. • Dust emission and transport processes required for better PM 2.5 predictions. [ABSTRACT FROM AUTHOR]

Abstract Background:: Rates of smoking in East Asian men range from >35% to >60%, and are increasing in women and the young. Objective:: This study evaluated the efficacy and tolerability of 1 mg BID varenicline, a novel α4β2 nicotinic acetylcholine receptor partial agonist, for smoking cessation in smokers in Taiwan and Korea. Methods:: A randomized, double-blind, placebo-controlled, 12-week treatment, 12-week follow-up trial was conducted at 5 sites each in Korea and Taiwan. Eligible subjects, smoking ≥10 cigarettes/d, received brief smoking-cessation counseling and were randomly assigned in a 1:1 ratio to varenicline 1 mg BID (titrated during the first week) or placebo. Smoking status was established by self-report and confirmed at clinic visits by end-expiratory carbon monoxide ≤10 ppm. The primary end point was continuous abstinence rate (CAR) during the last 4 weeks of treatment. Secondary end points included CAR from weeks 9 to 24 and 7-day point prevalence (PP) of abstinence at weeks 12 and 24. Craving, withdrawal, and smoking satisfaction were determined by the Minnesota Nicotine Withdrawal Scale, the Brief Questionnaire of Smoking Urges, and the modified Cigarette Evaluation Questionnaire. Observed or volunteered adverse-event data were recorded at clinic visits. Results:: Overall, 126 subjects (84.9% male) received varenicline, and 124 (92.7% male) received placebo, Subjects were aged 21 to 73 years (mean age, 39.7 and 40.9 years for varenicline and placebo groups, respectively), and the mean (range) body weights were 69.0 (44.8–110.0) kg and 71.4 (45.5–102.0) kg, respectively. Subjects had smoked for 3 to 52 years (mean, 20.2 and 22.1 years in the varenicline and placebo groups, respectively). Subjects had smoked a mean of 23 cigarettes/d over the past month, with 51.6% (varenicline) and 46.0% (placebo) having made 1 or more prior serious quit attempts. Smoking-cessation rates at the end of treatment were 59.5% with varenicline versus 32.3% with placebo (P < 0.001). CARs through 12 weeks post-treatment (weeks 9–24) were 46.8% with varenicline and 21.8% with placebo (P < 0.001). The 7-day PP was 67.5% with varenicline versus 36.3% with placebo at week 12, and 57.1% versus 29.0% with placebo at week 24 (both, P < 0.001). Treatment-emergent, all-causality adverse events with an incidence ≥ 5% for varenicline were nausea (43.7% for varenicline vs 11.3% placebo), insomnia (15.1% vs 13.7%), increased appetite (7.9% vs 6.5%), constipation (7.1% vs 2.4%), anxiety (5.6% vs 2.4%), and abnormal dreams (5.6% vs 0.8%). Adverse events resulted in <10% treatment discontinuations overall. Conclusion:: Varenicline was an efficacious and well-tolerated pharmacotherapy for smoking cessation in this group of Asian smokers over a 12-week treatment period, and its effects persisted for a further 12-week follow-up period. [Copyright &y& Elsevier]