© 2020 by the authors. In this study, the results for nitrate (NO3-) aerosol during winter from the first-phase model inter-comparison study of Japan's Study for Reference Air Quality Modeling (J-STREAM) were analyzed. To investigate the models' external and internal settings, the results were limited to Community Multiscale Air Quality (CMAQ) models. All submitted models generally underestimated NO3-over the urban areas in Japan (e.g., Osaka, Nagoya, and Tokyo); however, some model settings showed distinct behavior. The differences due to the model external settings were larger than the model internal settings. Emissions were an important factor, and emissions configured with lower NOx emissions and higher NH3 emissions led to a higher NO3-concentration as the NH3 was consumed under NH3-rich conditions. The model internal settings of the chemical mechanisms caused differences over China, and this could affect western Japan; however, the difference over Tokyo was lower. To obtain a higher NO3-concentration over the urban areas in Japan, the selection of the HONO option for the heterogenous reaction and the inline calculation of photolysis was desired. For future studies, the external settings of the boundary condition and the meteorological field require further investigation.

A model inter-comparison of secondary pollutant simulations over urban areas in Japan, the first phase of Japan’s study for reference air quality modeling (J-STREAM Phase I), was conducted using 32 model settings. Simulated hourly concentrations of nitric oxide (NO) and nitrogen dioxide (NO2), which are primary pollutant precursors of particulate matter with a diameter of 2.5 µm or less (PM2.5), showed good agreement with the observed concentrations, but most of the simulated hourly sulfur oxide (SO2) concentrations were much higher than the observations. Simulated concentrations of PM2.5 and its components were compared to daily observed concentrations by using the filter pack method at selected ambient air pollution monitoring stations (AAPMSs) for each season. In general, most models showed good agreement with the observed total PM2.5 mass concentration levels in each season and provided goal or criteria levels of model ensemble statistics in warmer seasons. The good performances of these models were associated with the simulated reproducibility of some dominant components, sulfates (SO42−) and ammonium (NH4+). The other simulated PM2.5 components, i.e., nitrates (NO3−), elemental carbon (EC), and organic carbon (OC), often show clear deviations from the observations. The considerable underestimations (approximately 30 µg/m3 for total PM2.5) of all participant models found on heavily polluted days with approximately 40–50 µg/m3 for total PM2.5 indicated some problems in the simulated local meteorology such as the atmospheric stability. This model inter-comparison suggests that these deviations may be owing to a need for further improvements both in the emission inventories and additional formation pathways in chemical transport models, and meteorological conditions also require improvement to simulate elevated atmospheric pollutants. Additional accumulated observations are likely needed to further evaluate the simulated concentrations and improve the model performance.

Ozone is one of remaining air quality issues in Japan. Effective strategies are required to reduce ozone at the ground level. Regional chemical transport models are useful in investigating relationships between precursor emissions and ambient concentrations of secondary pollutants including ozone. Model performance on ozone concentrations over urban areas in Japan were thoroughly evaluated in model inter-comparisons conducted in Japan's study for reference air quality modeling (J-STREAM). Specifically, 33 models with different configurations including the Community Multiscale Air Quality Modeling System (CMAQ), the Comprehensive Air Quality Model with Extensions (CAMx), and the Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem) participated. They realized inter-comparisons with an unprecedented number of different model configurations. All the participating models overestimated ozone concentrations by 22 ± 4.6 ppb over urban areas in Japan during the summer. Spatial and temporal variations in model performance suggest the influence of background ozone concentrations. Based on differences in the participating model configurations, halogen chemistry and deposition, dry deposition velocity, precursor emissions in other countries, and vertical transport were identified as the key factors influencing simulated background ozone concentrations. Specific sensitivity analyses were conducted to evaluate the effects of the key influencing factors. Halogen chemistry and deposition implemented in recent versions of CMAQ caused more than 10 ppb reduction of simulated ozone over the ocean surrounding Japan, while the original dry deposition schemes used in CAMx and WRF-Chem, without any effect of halogen, can also cause larger dry deposition. Horizontal and downward transport of ozone kept in a residual layer over the continent can spread the effect of precursor emissions in other countries to downwind regions, including Japan. Differences in vertical transport can alter the spatial extent of their effects. It is essential to improve the influence of the aforementioned key factors to realize better model performance on ozone concentrations over urban areas, not only in Japan, but all over the world.

© 2019 by the authors. During the Japanese intercomparison study, Japan's Study for Reference Air Quality Modeling (J-STREAM), it was found that wintertime SO42- concentrations were underestimated over Japan with the Community Multiscale Air Quality (CMAQ) modeling system. Previously, following two development phases, model performance was improved by refining the Fe- and Mn-catalyzed oxidation pathways and by including an additional aqueous-phase pathway via NO2 oxidation. In a third phase, we examined a winter haze period in December 2016, involving a gas-phase oxidation pathway whereby three stabilized Criegee intermediates (SCI) were incorporated into the model. We also included options for a kinetic mass transfer aqueous-phase calculation. According to statistical analysis, simulations compared well with hourly SO42- observations in Tokyo. Source sensitivities for four domestic emission sources (transportation, stationary combustion, fugitive VOC, and agricultural NH3) were investigated. During the haze period, contributions from other sources (overseas and volcanic emissions) dominated, while domestic sources, including transportation and fuel combustion, played a role in enhancing SO42- concentrations around Tokyo Bay. Updating the aqueous phase metal catalyzed and NO2 oxidation pathways lead to increase contribution from other sources, and the additional gas phase SCI chemistry provided a link between fugitive VOC emission and SO42- concentration via changes in O3 concentration.

© 2019 by Asian Journal of Atmospheric Environment. Hourly concentrations of fine particulate OC and EC are monitored for more than one year by optical monitors at three sites in and out of Tokyo, Japan. Distances between the sites are 20 to 50 km. SOC concentrations are estimated from the OC and EC concentrations by an EC tracer method. Site A in an industrial site shows higher EC concentrations than site B in a residential area, but differences between the sites are much reduced for OC. Site C in a rural area, where measurements are available in colder months, shows pronounced seasonal variations with high peaks in October and December and characteristic diurnal variations in OC with the highest in the evening in October, due probably to open field burning. Photochemical formation of SOC is suggested but does not rise up so much OC concentrations in summer, which are quite lower than other seasons. A comparison between relative concentrations of EC among the sites and local emissions amounts indicates missing or considerable underestimation of EC emissions near the rural site C. Time lag correlations suggest transport of OC produced by open field burning around site C to site A. These findings would be useful for improving model performances in OC/EC predictions.

© 2018 by the authors. Sulfate aerosol (SO 42- ) is a major component of particulate matter in Japan. The Japanese model intercomparison study, J-STREAM, found that although SO 42- is well captured by models, it is underestimated during winter. In the first phase of J-STREAM, we refined the Fe- and Mn-catalyzed oxidation and partly improved the underestimation. The winter haze in December 2016 was a target period in the second phase. The results from the Community Multiscale Air Quality (CMAQ) and Comprehensive Air quality Model with eXtentions (CAMx) regional chemical transport models were compared with observations from the network over Japan and intensive observations at Nagoya and Tokyo. Statistical analysis showed both models satisfied the suggested model performance criteria. CMAQ sensitivity simulations explained the improvements in model performance. CMAQ modeled lower SO 42- concentrations than CAMx, despite increased aqueous oxidation via the metal catalysis pathway and NO 2 reaction in CMAQ. Deposition explained this difference. A scatter plot demonstrated that the lower SO 42- concentration in CMAQ than in CAMx arose from the lower SO 2 concentration and higher SO 42- wet deposition in CMAQ. The dry deposition velocity caused the difference in SO 2 concentration. These results suggest the importance of deposition in improving our understanding of ambient concentration behavior.

Since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in March 2011, atmospheric simulation models have improved our understanding of the atmospheric behavior of radionuclides. Model intercomparisons provide valuable and useful information for evaluating the validity and variability of individual model results. In this study, we compared results of seven atmospheric transport models used to simulate 137Cs released from the FDNPP to the atmosphere. All model results used in this analysis had been submitted for a model intercomparison project of the Science Council of Japan (2014, http://www.scj.go.jp/en/report/index.html). Here we assessed model performance by comparing model results with observed hourly atmospheric concentrations of 137Cs, with a particular focus on nine plumes over the Tohoku and Kanto regions. The intercomparison results showed that model performance in reproducing 137Cs concentrations was highly variable among different models and plumes. In general, models better reproduced plumes that passed over many observation stations. The performance among the models was consistent with the simulated wind fields and the source terms used. We also assessed model performance in relation to accumulated 137Cs deposition. Simulated areas of high 137Cs deposition were consistent with the simulated 137Cs plume pathways, though the models that best simulated atmospheric 137Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced atmospheric 137Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.

© 2018, Korean Society for Atmospheric Environment. The urban model inter-comparison study (UMICS) was conducted in order to improve the performance of air quality models (AQMs) for simulating fine particulate matter (PM2.5) in the Greater Tokyo Area of Japan. UMICS consists of three phases: the first phase focusing on elemental carbon (UMICS1), the second phase focusing on sulfate, nitrate and ammonium (UMICS2), and the third phase focusing on organic aerosol (OA) (UMICS 3). In UMICS2/3, all the participating AQMs were the Community Multiscale Air Quality modeling system (CMAQ) with different configurations, and they similarly overestimated PM2.5 nitrate concentration and underestimated PM2.5 OA concentration. Various sensitivity analyses on CMAQ configurations, emissions and boundary concentrations, and meteorological fields were conducted in order to seek pathways for improvement of PM2.5 simulation. The sensitivity analyses revealed that PM2.5 nitrate concentration was highly sensitive to emissions of ammonia (NH3) and dry deposition of nitric acid (HNO3) and NH3, and PM2.5 OA concentration was highly sensitive to emissions of condensable organic compounds (COC). It was found that PM2.5 simulation was substantially improved by using modified monthly profile of NH3 emissions, larger dry deposition velocities of HNO3 and NH3, and additionally estimated COC emissions. Moreover, variability in PM2.5 simulation was estimated from the results of all the sensitivity analyses. The variabilities on CMAQ configurations, chemical inputs (emissions and boundary concentrations), and meteorological fields were 6.1-6.5, 9.7-10.9, and 10.3-12.3%, respectively.

© 2018 by the authors. We refined the aqueous-phase sulfate (SO42-) production in the state-of-the-art Community Multiscale Air Quality (CMAQ) model during the Japanese model inter-comparison project, known as Japan's Study for Reference Air Quality Modeling (J-STREAM). In Japan, SO42- is the major component of PM2.5, and CMAQ reproduces the observed seasonal variation of SO42- with the summer maxima and winter minima. However, CMAQ underestimates the concentration during winter over Japan. Based on a review of the current modeling system, we identified a possible reason as being the inadequate aqueous-phase SO42- production by Fe- and Mn-catalyzed O2 oxidation. This is because these trace metals are not properly included in the Asian emission inventories. Fe and Mn observations over Japan showed that the model concentrations based on the latest Japanese emission inventory were substantially underestimated. Thus, we conducted sensitivity simulations where the modeled Fe and Mn concentrations were adjusted to the observed levels, the Fe and Mn solubilities were increased, and the oxidation rate constant was revised. Adjusting the concentration increased the SO42- concentration during winter, as did increasing the solubilities and revising the rate constant to consider pH dependencies. Statistical analysis showed that these sensitivity simulations improved model performance. The approach adopted in this study can partly improve model performance in terms of the underestimation of SO42- concentration during winter. From our findings, we demonstrated the importance of developing and evaluating trace metal emission inventories in Asia.

Acidifying species in precipitation can have severe impacts on ecosystems. The chemical composition of precipitation is directly related to the amount of precipitation
accordingly, it is difficult to identify long-term variation in chemical concentrations. The ratio of the nitrate (NO3) to non-sea-salt sulfate (nss-SO42) concentration in precipitation on an equivalent basis (hereinafter, Ratio) is a useful index to investigate the relative contributions of these acidifying species. To identify the long-term record of acidifying species in precipitation over East Asia, the region with the highest emissions worldwide, we compiled ground-based observations of the chemical composition of precipitation over China, Korea, and Japan from 2001 to 2015 based on the Acid Deposition Monitoring Network in East Asia (EANET). The spatial coverage was limited, but additional monitoring data for Japan, southern China, and northern China around Beijing were utilized. The period of analysis was divided into three phases: Phase I (2001-2005), Phase II (2006-2010), and Phase III (2011-2015). The behaviors of NO3 and nss-SO42 concentrations and hence the Ratio in precipitation were related to these precursors. The anthropogenic NOx and SO2 emissions and the NOxg•SO2 emission ratio were analyzed. Further, satellite observations of the NO2 and SO2 column density to capture the variation in emissions were applied. We found that the long-term trend in the NO3 concentration in precipitation was not related to the variation in NOx emission and the NO2 column. In comparison, the nss-SO42 concentration in precipitation over China, Korea, and Japan was partially connected to the changes in SO2 emissions from China, but the trends were not significant. The long-term trends of Ratio over China, Korea, and Japan were nearly flat during Phase I, increased significantly during Phase II, and were essentially flat again during Phase III. This variation in Ratio in East Asia clearly corresponded to the NOxg•SO2 emission ratio and the NO2g•SO2 column ratio in China. The initial flat trend during Phase I was due to increases in both NOx and SO2 emissions in China, the significantly increasing trend during Phase II was triggered by the increase in NOx emissions and decrease in SO2 emissions in China, and the return to a flat trend during Phase III was caused by declines in both NOx and SO2 emissions in China. These results suggest that emissions in China had a significant impact not only on China but also on downwind precipitation chemistry during the 15-year period of 2001-2015. In terms of wet deposition, the NO3 wet deposition over China, Korea, and Japan did not change dramatically, but the nss-SO42 wet deposition declined over China, Korea, and Japan from Phase II to III. These declines were caused by a strong decrease in the nss-SO42 concentration in precipitation accompanied by a reduction in SO2 emission from China, which counteracted the increase in precipitation. These findings indicated that the acidity of precipitation shifted from sulfur to nitrogen.

© 2018 by the authors. The inter-comparison of regional air quality models is an effective way to understand uncertainty in ambient pollutant concentrations simulated using various model configurations, as well as to find ways to improve model performance. Based on the outcomes and experiences of Japanese projects thus far, a new model inter-comparison project called Japan's study for reference air quality modeling (J-STREAM) has begun. The objective of J-STREAM is to establish reference air quality modeling for source apportionment and effective strategy making to suppress secondary air pollutants including PM2.5 and photochemical ozone in Japan through model inter-comparison. The first phase focuses on understanding the ranges and limitations in ambient PM2.5 and ozone concentrations simulated by participants using common input datasets. The second phase focuses on issues revealed in previous studies in simulating secondary inorganic aerosols, as well as on the three-dimensional characteristics of photochemical ozone as a new target. The third phase focuses on comparing source apportionments and sensitivities under heavy air pollution episodes simulated by participating models. Detailed understanding of model performance, uncertainty, and possible improvements to urban-scale air pollution involving secondary pollutants, as well as detailed sector-wise source apportionments over megacities in Japan are expected.

<p>We have been monitoring the air pollutants at the Tokyo Skytree (TST) in order to understand the air quality over central Tokyo. Focusing on the haze event on the 9th and 10th December 2015, we analyzed the causes of the event and differences in the air quality between the ground and upper levels. In the afternoon on Dec. 9, as a result, higher concentrations of SO<sub>2</sub> were observed at 320 m AGL on Tokyo Skytree (H320) than near the ground surface (H10). It is likely that a boundary layer was formed from 18:00, and H320 had been influenced by large-point sources and ships. In the night of Dec. 10 when the PM<sub>2.5</sub> concentrations went over 90 μg/m<sup>3</sup> around central Tokyo, an inversion layer was formed associated with a local front (the so-called the Boso front line). This polluted air mass seemed to be centered at the southeastern part of the 23 wards of Tokyo and distributed below 200 m AGL from 22:00 to 23:00. We also found that the number concentration ratios (N<sub>H320</sub>/N<sub>H10</sub>) of smaller particles measured at H320 to H10 increased earlier than those of the larger particles.</p>

Appropriate policies to improve air quality by reducing anthropogenic emissions are urgently needed. This is typified by the particulate matter (PM) problem and it is well known that one type of PM, sulfate aerosol (SO42-), has a large-scale impact due to long range transport. In this study we evaluate the source receptor relationships of SOi-over East Asia for 2005, when anthropogenic sulfur dioxide (SO2) emissions from China peaked. SO2 emissions from China have been declining since 2005-2006, so the possible maximum impact of Chinese contributions of SO42- is evaluated. This kind of information provides a foundation for policy making and the estimation of control effects. The tagged tracer method was applied to estimate the source apportionment of SO42- is for 31 Chinese province-scale regions. In addition, overall one-year source apportionments were evaluated to clarify the seasonal dependency. Model performance was confirmed by comparing with ground-based observations over mainland China, Taiwan, Korea, and Japan, and the model results fully satisfied the performance goal for PM. We found the following results. Shandong and Hebei provinces, which were the largest and second largest SO2 sources in China, had the greatest impact over the whole of East Asia with apportionments of around 10-30% locally and around 5-15% in downwind receptor regions during the year. Despite large SO2 emissions, the impact of south China (e.g., Guizhou, Guangdong, and Sichuan provinces) was limited to local impact. These results suggest that the reduction policy in south China contributes to improving the local air quality, whereas policies in north and central China are beneficial for both the whole of China and downwind regions. Over Taiwan, Korea, and Japan, the impact of China was dominant; however, local contributions were important during summer. (C) 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.

<p>Source apportionments of PM_2.5 in Japan on 2010 fiscal year were evaluated based on the air quality model by applying the tagged tracer method. Source groups were divided into the total of 15; 10 domestic anthropogenic source, 3 foreign anthropogenic sources from China, Korea, and other regions, and ships and natural sources. The performances of the air quality model were validated through statistical analysis. Annual mean source apportionments averaged over Japan was the largest with 3.60 μg/m³ (33.9% as relative percentages) from domestic anthropogenic source and the second largest with 3.10 μg/m³ (29.2%) from anthropogenic emissions of China. Domestic source had the impacts in the following order; vehicle (7.4%), manufacturing industry (7.0%), livestock (5.5%), rest of domestic sources (5.4%), fertilization (2.8%), and power plant, machines, business boilers, waste incinerator (approximately 1–2%). From the viewpoint of long- and short-term standards, source apportionments were further evaluated for attainment and non-attainment sites. The results showed that the dominant influence of the transboundary air pollution over the Kyushu region especially for short-term standard. Over the Setouchi region, the impacts from manufacturing industry and ships were large. The attribution from vehicle was also important in the Kinki region. In the Kanto region, both of vehicle and manufacturing industry attributions were important for short-term standard, but vehicle was more significant source for long-term standard.</p>

The atmospheric input of anthropogenic total reactive oxygenated nitrogen (NOy) to ocean regions in East Asia during 2002-2004 was revisited with an updated regional chemical transport model and the latest emissions inventory. The updated model treats both fine- and coarse-mode nitrate (NO3-). Coarse-mode NO3- is produced by the reaction of nitric acid (HNO3) and sea salt particles. The modeling system reproduced the atmospheric concentration and wet deposition amount of NO3- quantitatively compared with observations. The fraction of coarse-mode NO3- was also well captured. NOy deposition amounts over marginal seas and open oceans were 733 and 730 Gg N/yr, which are increases of 1.6- and 2.2-fold, respectively, by including coarse-mode NO3-. Anthropogenic NOx emissions from China were 5377 Gg N/yr, and 3060 Gg N/yr was exported from China; therefore, the NOy deposition amount over ocean regions in East Asia (1463 Gg N/yr) corresponded to almost half (48%) of the export amounts.

&lt;p&gt;This paper describes the gaseous organic carbon (OC) concentration in the PM&lt;sub&gt;2.5&lt;/sub&gt; and positive artifact. The observations were done from April 2014 to March 2015 in Komae, Tokyo. In order to understand the influence of the gaseous OC, the measuring devices equipped with a denuder (denuder-filter method) and without a denuder (filter method) were simultaneously operated in parallel. The samples were analyzed for the OC concentrations by a thermal optical reflectance (TOR) method using a carbon analyzer manufactured by Sunset Laboratory. The average organic carbon concentrations were 2.8 μgC/m&lt;sup&gt;3&lt;/sup&gt; (filter method) and 1.7 μgC/m&lt;sup&gt;3&lt;/sup&gt; (denuder-filter method). The mean gaseous OC concentration was estimated to be 1.1 μgC/m&lt;sup&gt;3&lt;/sup&gt;. It turned out that about 39% was the gaseous OC among the OC concentrations in the PM&lt;sub&gt;2.5&lt;/sub&gt;.&lt;/p&gt;

Changes in anthropogenic emissions in East Asia will cause substantial variations in the precipitation chemistry. In particular, the effects of changes in China, where NOx emissions have been rising continuously and SO2 emissions peaked in 2005-2006, are important. The absolute chemical concentration in precipitation is inherently linked to the amount of precipitation; therefore, in this work we d) used the ratio of nitrate (NO3-) to non-seasalt sulfate (nss-SO42-) concentration in precipitation on an equivalent basis (hereinafter, Ratio). Here, we extend the method our previous study (Itahashi et al., 2014a) to Korea and China. We analyzed the long-term behavior of Ratio in precipitation during 2000-2011 and investigated the factors responsible for variations of Ratio in precipitation by using a model simulation with sensitivity analysis for emission changes in China. Ratio over Japan, Korea, and China decreased slightly or remained constant during 2000-2005 (first 6 years of 2000-2011) and subsequently increased during 2006-2011 (last 6 years of 2000-2011). Linear regression analysis of the observations showed significant increases in Ratio during 2006-2011: +3.4 +/- 1.0%/year, +13.2 +/- 4.1%/year, and +9.8 +/- 2.5%/year for Japan, Korea, and China, respectively (each p &lt; 0.05). These variations in Ratio corresponded closely to the changes in the NOx/SO2 emission ratio in China. This suggests that anthropogenic emissions from China were responsible for most of the variation in precipitation chemistry in East Asia. Model simulations for 2000-2011 and their reproducibility were validated by comparison with the observation dataset, and they captured the observed features well. Sensitivity analysis of emissions from China in the model simulation for 2009-2011 clarified that the increase in NOx emissions from China contributed to 55-60% of the increase in Ratio in China and around 50-55% in Korea and Japan; the contribution of the increase in NOx emissions was smaller in the region downwind of China. In contrast, the decline in SO2 emissions from China contributed below 40% in China and around 40-45% in Japan; the effect was larger in the region downwind of China. (C) 2015 The Authors. Published by Elsevier Ltd.

Emission source contributions of tropospheric ozone (O3) were comprehensively investigated by using the higher-order decoupled direct method (HDDM) for sensitivity analysis and the ozone source apportionment technology (OSAT) for mass balance analysis in the comprehensive air-quality model with extensions (CAMx). The response of O to emissions reductions at various levels in mainland China, Korea, and Japan were estimated and compared with results calculated by the brute force method (BFM) where one model parameter is varied at a time. Emissions were assessed at three receptor sites in Japan that experienced severe pollution events in May 2009. For emissions from China, HDDM assessed O3 response with a bias of only up to 3 ppbv (a relative error of 4.5%) even for a 50% reduction but failed to assess a more extreme reduction. OSAT was reasonably accurate at 100% reduction, with a −4 ppbv (−7%) bias, but was less accurate at moderate ranges of reduction (∼50-70%). For emissions from Korea and Japan, HDDM captured the nonlinear response at all receptor sites and at all reduction levels to within 1% in all but one case
however, the bias of OSAT increased with the increasing reduction of emissions. One possible reason for this is that OSAT does not account for NO titration. To address this, a term for potential ozone (PO
O3and NO2 together) was introduced. Using of PO instead of O3 improved the performance of OSAT, especially for emissions reductions from Korea and Japan. The proposed approach with PO refined the OSAT results and did not degrade HDDM performance.

In recent years, the concentrations of precursors of ozone have been decreasing in Japan, but the ground-level ozone concentrations tend to increase. During the summertime in the Kanto region, anthropogenic emission control in Japan is an important factor for decreasing the ozone concentration. In this study, we conducted an air quality simulation using WRF and CMAQ with the anthropogenic emissions data in 2000 and 2005 to verify the effect of the emission controls between 2000 and 2005 on the ozone concentration in the Kanto region. The NO&lt;sub&gt;x&lt;/sub&gt; and VOC reductions contribute to the increase in the daytime maximum ozone in the central Tokyo surrounding area but to the decrease in the other areas of the Kanto region. For the NO&lt;sub&gt;x&lt;/sub&gt; reduction case, the daytime maximum ozone was increased in a wide area of the plains. On the other hand, The VOC reduction effectively works to decrease the ozone concentration in the entire Kanto area. Based on the results of the ozone sensitive analysis for a high concentration day, the NO&lt;sub&gt;x&lt;/sub&gt; sensitive and mixed sensitive regime account for half of the number of occurrences in inland Kanto area. Howeber, the VOC sensitive regime was the majority in the large city. These results show the effectiveness of the reduction of precursors to the decrease in the ozone concentration in each area of Kanto.

Source apportionments of domestic/overseas impacts on non-seasalt sulfate aerosol (nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;) concentration in Japan were analyzed on the basis of tagged tracer method in regional chemical transport model. The emission source groups were categorized into anthropogenic sources from China, Korea, and Japan, and natural sources from volcanic activity. To investigate the seasonal dependency of source apportionments, the representative months of January, April, July, and October on the year of 2005 were chosen in this analysis. A distinguishable feature of this study is that source apportionments of sulfur dioxide (SO&lt;sub&gt;2&lt;/sub&gt;), which is a precursor of nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;, were also investigated. Modeling system with 36 km horizontal resolution well captured the seasonal variability of both SO&lt;sub&gt;2&lt;/sub&gt; and nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;. In Japan, domestic impacts on SO&lt;sub&gt;2&lt;/sub&gt; concentration was leading contributor (66.3% on average), however, transboundary air pollution with the contribution from China was dominant throughout seasons for nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; (50.6% on average). This is because the SO&lt;sub&gt;2&lt;/sub&gt; concentration in China was one order of magnitude greater than that in Japan, therefore, nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; was chemically produced during long-range transport. During summer, SO&lt;sub&gt;2&lt;/sub&gt; emitted from China was fully (&gt; 95%) converted into nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; and affected Japan. Impact from volcanic activity was also identified as the major contributor of nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; concentration in Japan; they surpassed the anthropogenic Japanese domestic impacts during spring and autumn.

Increasing ozone concentrations are observed over Japan from year to year. One cause of high ozone concentration in the Kanto region, which includes areas inland from large coastal cities such as metropolitan Tokyo, is the transportation of precursors by sea breezes. However, high ozone concentrations are also observed in the morning, before sea breezes approach inland areas. In this point, there would be a possibility of residual ozone existing above the nocturnal boundary layer affects the ozone concentration in the following morning. In this study, we utilized the Weather Research and Forecasting model and the Community Multiscale Air Quality model to evaluate the effect of regional precursors and residual ozone on ozone concentrations over the inland Kanto region. The results show that precursors emitted from non-metropolitan areas affected inland ozone concentrations more than did precursors from metropolitan areas. Moreover, calculated results indicate downward transportation of residual ozone, resulting in increased concentration. The residual ozone was also affected by precursors emitted from non-metropolitan areas.

Emission source contributions of tropospheric ozone (O-3) were comprehensively investigated by using the higher-order decoupled direct method (HDDM) for sensitivity analysis and the ozone source apportionment technology (OSAT) for mass balance analysis in the comprehensive air-quality model with extensions (CAMx). The response of O-3 to emissions reductions at various levels in mainland China, Korea, and Japan were estimated and compared with results calculated by the brute force method (BFM) where one model parameter is varied at a time. Emissions were assessed at three receptor sites in Japan that experienced severe pollution events in May 2009. For emissions from China, HDDM assessed O-3 response with a bias of only up to 3 ppbv (a relative error of 4.5%) even for a 50% reduction but failed to assess a more extreme reduction. OSAT was reasonably accurate at 100% reduction, with a -4 ppbv (-7%) bias, but was less accurate at moderate ranges of reduction (approximate to 50-70%). For emissions from Korea and Japan, HDDM captured the nonlinear response at all receptor sites and at all reduction levels to within 1% in all but one case; however, the bias of OSAT increased with the increasing reduction of emissions. One possible reason for this is that OSAT does not account for NO titration. To address this, a term for potential ozone (PO; O-3 and NO2 together) was introduced. Using of PO instead of O-3 improved the performance of OSAT, especially for emissions reductions from Korea and Japan. The proposed approach with PO refined the OSAT results and did not degrade HDDM performance.
Key Points

Anthropogenic emissions in East Asia have been increasing during the three decades since 1980, as the population of East Asia has grown and the economies in East Asian countries have expanded. This has been particularly true in China, where NOx emissions have been rising continuously. However, because of fuel-gas desulfurization systems introduced as part of China's 11th Five-Year Plan (2006-2010), SO2 emissions in China reached a peak in 2005-2006 and have declined since then. These drastic changes in emission levels of acidifying species are likely to have caused substantial changes in the precipitation chemistry. The absolute concentration of compounds in precipitation is inherently linked to precipitation amount; therefore, we use the ratio of nitrate (NO3-) to non-seasalt sulfate (nss-SO42-) concentration in precipitation as an index for evaluating acidification, which we call Ratio. In this study, we analyzed the long-term behavior of Ratio in precipitation over the Japanese archipelago during 2000-2011 and estimated the factors responsible for changes in Ratio in precipitation by using a model simulation. This analysis showed that Ratio was relatively constant at 0.5-0.6 between 2000 and 2005, and subsequently increased to 0.6-0.7 between 2006 and 2011. These changes in Ratio corresponded remarkably well to the changes of NOx/SO2 emissions ratio in China; this correspondence suggests that anthropogenic emissions from China were responsible for most of the change in precipitation chemistry over Japan. Sensitivity analysis elucidated that the increase in NOx emissions and the decrease in SO2 emissions contributed equally to the increases in Ratio. Considering both emission changes in China enables to capture the observed increasing trend of Ratio in Japan. (C) 2014 Elsevier Ltd. All rights reserved.

Improvement of air quality models is required so that they can be utilized to design effective control strategies for fine particulate matter (PM2.5). The Community Multiscale Air Quality modeling system was applied to the Greater Tokyo Area of Japan in winter 2010 and summer 2011. The model results were compared with observed concentrations of PM2.5 sulfate (SO42-), nitrate (NO3-) and ammonium, and gaseous nitric acid (HNO3) and ammonia (NH3). The model approximately reproduced PM2.5 SO42- concentration, but clearly overestimated PM2.5 NO3- concentration, which was attributed to overestimation of production of ammonium nitrate (NH4NO3). This study conducted sensitivity analyses of factors associated with the model performance for PM2.5 NO3- concentration, including temperature and relative humidity, emission of nitrogen oxides, seasonal variation of NH3 emission, HNO3 and NH3 dry deposition velocities, and heterogeneous reaction probability of dinitrogen pentoxide. Change in NH3 emission directly affected NH3 concentration, and substantially affected NH4NO3 concentration. Higher dry deposition velocities of HNO3 and NH3 led to substantial reductions of concentrations of the gaseous species and NH4NO3. Because uncertainties in NH3 emission and dry deposition processes are probably large, these processes may be key factors for improvement of the model performance for PM2.5 NO3-.Implications:The Community Multiscale Air Quality modeling system clearly overestimated the concentration of fine particulate nitrate in the Greater Tokyo Area of Japan, which was attributed to overestimation of production of ammonium nitrate. Sensitivity analyses were conducted for factors associated with the model performance for nitrate. Ammonia emission and dry deposition of nitric acid and ammonia may be key factors for improvement of the model performance.

The first phase of the Urban air quality Model InterComparison Study in Japan (UMICS) has been conducted to find ways to improve model performance with regard to elemental carbon (EC). Common meteorology and emission datasets are used with eight different models. All the models underestimate the EC concentrations observed in Tokyo Metropolitan Area in the summer of 2007. Sensitivity analyses are conducted using these models to investigate the causes of this underestimation. The results of the analyses reveal that emissions and vertical diffusion are dominant factors that affect the simulated EC concentrations. A significant improvement in the accuracy of EC concentrations could be realized by applying appropriate scaling factors to EC emissions and boundary concentrations. Observation data from Lidar and radiosonde suggest the possible overestimation of planetary boundary layer height, which is a vital parameter representing vertical diffusion. The findings of this work can help to improve air quality models to that they can be used to develop more effective strategies for reducing PM2.5 concentrations.

Ground-based PM&lt;sub&gt;2.5&lt;/sub&gt; observations were compared with the space-borne observed aerosol optical depth (AOD). Decadal-scale observations at 5 sites in Japan and the observation by the U.S. embassy at Beijing in China were utilized. Measurements by MODIS onboard Terra and Aqua have been detecting AOD from space since February 2000 and July 2002, respectively. The monthly averaged PM&lt;sub&gt;2.5&lt;/sub&gt; and AOD at each site corresponded with correlation coefficients around 0.7 both in the morning and afternoon except for Osaka and Beijing. The coverage threshold of monthly data in MODIS dataset was considered as an important factor to evaluate the correspondence of AOD with ground-based PM&lt;sub&gt;2.5&lt;/sub&gt;, especially at Beijing. When the threshold value of MODIS monthly coverage was set at 40%, the averaged correlation coefficient at 6 sites in Japan and China showed correlation coefficient of 0.63 with a statistically significance level. PM&lt;sub&gt;2.5&lt;/sub&gt; and AOD also had a spatial correlation. As an example of application, on the basis of sound relationships between PM&lt;sub&gt;2.5&lt;/sub&gt; and AOD, episodic events of high PM&lt;sub&gt;2.5&lt;/sub&gt; concentrations in Beijing occurred during January 2013 were assessed, and the results indicated that a dramatic increase of PM&lt;sub&gt;2.5&lt;/sub&gt; around Japan were not found during that episode.

In winter 2013, extreme air pollution by fine particulate matter (PM2.5) in China attracted much public attention. In order to simulate the PM2.5 pollution, the Community Multiscale Air Quality model driven by the Weather Research and Forecasting model was applied to East Asia in a period from 1 January 2013 to 5 February 2013. The model generally reproduced PM2.5 concentration in China with emission data in the year 2006. Therefore, the extreme PM2.5 pollution seems to be mainly attributed to meteorological (weak wind and stable) conditions rather than emission increases in the past several years. The model well simulated temporal and spatial variations in PM2.5 concentrations in Japan as well as China, indicating that the model well captured characteristics of the PM2.5 pollutions in both areas on the windward and leeward sides in East Asia in the study period. In addition, contribution rates of four anthropogenic emission sectors (power generation, industrial, residential and transportation) in China to PM2.5 concentration were estimated by conducting zero-out emission sensitivity runs. Among the four sectors, the residential sector had the highest contribution to PM2.5 concentration. Therefore, the extreme PM2.5 pollution may be also attributed to large emissions from combustion for heating in cold regions in China.

© Crown Copyright 2014 Dstl. The urban air quality model inter-comParison study in Japan (UMICS) was conducted in order to improve the Community Multiscale Air Quality model (CMAQ) performance of the for PM2.5 simulation. UMICS consist of three phases including the first phase focusing on elemental carbon, the second phase focusing on major ionic components (sulfate, nitrate and ammonium) and the third phase focusing on organic aerosol (OA) (UMICS1, 2 and 3). The results of UMICS3 for improvement of substantial OA underestimation were described in this paper. Because primary OA accounted for most of OA in the participating models, changes in volatile organic compounds emissions caused only slight changes in OA concentrations. Meanwhile, additional primary OA emissions because of a large amount of semi-volatile organic compounds and condensable organic compounds emissions substantially increased OA concentrations. The results emphasized the importance of emission sources that were not considered in the existing emission data. In addition, sensitivity analyses on various processes including meteorology and emission were conducted in order to show errors of PM2.5 simulation originating from model input data and configurations. The results indicated that the importance of model input data is comparable to, or greater than that of model configurations in improvement of model performance for PM2.5 simulation.

In Northeast Asia, the effect of long-range transport of air pollutants is generally pronounced in spring and winter, but can be important even in summer. This study analyzed summer-time atmospheric transport of elemental carbon (EC) and sulfate (SO4 (2-)) with the Community Multiscale Air Quality (CMAQ) model driven by the Weather Research and Forecasting (WRF) model. The WRF/CMAQ modeling system was applied to regions ranging from Northeast Asia to the Greater Tokyo Area in Japan in summer 2007. In terms of EC, while the model simulated well the effect of long-range transport, the simulation results indicated that domestic emissions in Japan dominantly contributed (85%) to EC concentrations in the Greater Tokyo. In terms of SO4 (2-), the simulation results indicated that both domestic emissions (62%) and long-range transport from the other countries (38%) substantially contributed to SO4 (2-) concentrations in the Greater Tokyo. Distinctive transport processes of SO4 (2-) were associated with typical summer-time meteorological conditions in the study region. When a Pacific high-pressure system covered the main island of Japan, domestic emissions, including volcanic emission, dominantly contributed to SO4 (2-) concentrations in the Greater Tokyo. When a high-pressure system prevailed over the East China Sea and low-pressure systems passed north of Japan, synoptic westerly winds associated with this pressure pattern transported a large amount of SO4 (2-) from the continent to Japan. In addition, although heavy precipitation and strong wind decreased SO4 (2-) concentrations near the center of a typhoon, peripheral typhoon winds occasionally played an important role in long-range transport of SO4 (2-).

A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant following the Great East Japan Earthquake and tsunami of 11 March 2011 resulted in the release of radioactive materials to the ocean by two major pathways: direct release from the accident site and atmospheric deposition. A 1 yr, regional-scale simulation of Cs-137 activity in the ocean offshore of Fukushima was carried out, the sources of radioactivity being direct release, atmospheric deposition, and the inflow of Cs-137 deposited into the ocean by atmospheric deposition outside the domain of the model. Direct releases of Cs-137 were estimated for 1 yr after the accident by comparing simulated results and measured activities adjacent to the accident site. The contributions of each source were estimated by analysis of I-131/Cs-137 and Cs-134/Cs-137 activity ratios and comparisons between simulated results and measured activities of Cs-137. The estimated total amounts of directly released I-131, Cs-134, and Cs-137 were 11.1 +/- 2.2 PBq, 3.5 +/- 0.7 PBq, and 3.6 +/- 0.7 PBq, respectively. Simulated Cs-137 activities attributable to direct release were in good agreement with measured Cs-137 activities not only adjacent to the accident site, but also in a wide area in the model domain, therefore this implies that the estimated direct release rate was reasonable. Employment of improved nudging data by JCOPE2 improved both the offshore transport result and the reproducibility of Cs-137 activities 30 km offshore. On the other hand, simulated Cs-137 activities attributable to atmospheric deposition were low compared to measured activities. The rate of atmospheric deposition into the ocean was underestimated because of a lack of measurements of deposition into the ocean when atmospheric deposition rates were being estimated. Simulated Cs-137 activities attributable to the inflow of Cs-137 deposited into the ocean outside the domain of the model were in good agreement with measured activities in the open ocean within the model domain after June 2012. The consideration of inflow is important to simulate the Cs-137 activity in this model region in the later period of the simulation. The contribution of inflow increased with time and was dominant (more than 99 %) by the end of February 2012. The activity of directly released Cs-137, however, decreased exponentially with time and was detectable only in the coastal zone by the end of February 2012.

In recent years, the increasing photochemical oxidant concentration in Japan has been discussed as one of the social issues. In the Kanto area in the summer, the effect of transboundary air pollution is not very high, therefore, a domestic pollutant source could effect this issue. Based on previous studies, a high concentration of inland ozone results from the transportation of ozone from the south, the Tokyo Bay area and the Pacific Ocean driven by sea breezes. However some studies have shown that a high concentration of ozone was observed in the northern Kanto area, before the ozone from south arrives. To understand this ozone elevation in the northern Kanto area, we consider the contribution of the upper-layer ozone to the ground-level ozone by a box model with no chemical reactions. The difference between the simulated results and observed results at 12:00 is 30-60ppb. This difference would be caused by chemical reactions. From the doppler lidar observations and observations of the ozone concentration at Mt. Akagi, the ozone concentration was almost constant and about a 4 to 5 m/s horizontal wind blew on the night of July 27&lt;SUP&gt;th&lt;/SUP&gt; and August 4&lt;SUP&gt;th&lt;/SUP&gt; at a 1300m height. These results would mean that the northern Kanto area was covered by a constant concentration ozone and transported by the wind.

Organic carbon (OC) is a major component of PM2.5. Filer-sampled OC is often contaminated by gaseous organic carbons. The contamination likely varies with time and location. Before investigating it, we evaluate collection efficiencies of gases and particles by denuders, which may reduce the contamination. The collection efficiency is quite low for coarse particles and below 4 % even for sub-micron particles. Organic gases are mostly captured by the denuder.

Long-range transport of black carbon (BC) aerosol by the East Asian winter monsoon was simulated using the WRF/CMAQ modeling system. The temporal variations of observed and simulated BC concentrations were well agreed with each other at Fukue-jima and Chichijima. The results indicated that the model generally simulated the Asian outflow by the winter monsoon, which ensured the validity of the long-range horizontal advection process of the model. The concentration level of simulated BC tended to be lower than that of observed BC at Fulcue-jima but be close to at Chichijima. Therefore, the model may underestimate the magnitude of the vertical diffusion on ocean.

Simultaneous measurement of ambient aerosols was carried out using three aerosol mass spectrometers in the Kanto area during summer of 2011. Organic aerosol (OA) was detected as major component in this sampling campaign. The organic aerosol mass spectra was divided into two types of OA components, oxygenated organic aerosol (OOA) and hydrocarbon-like organic aerosol (HOA), using positive matrix factorization (PMF). The OOA was ubiquitous in various atmospheric environments, on average accounting for 44%, 49% and 55% of the total OA in Saitama (urban), Kazo (rural), and Maebashi (rural), respectively.

Simultaneous high-time resolution observations of PM2.5 components were carried out at four sites in Kanto area in summer and winter in order to get data sets for evaluation of air quality models and analyze factors of variation of PM2.5. The variations of PM2.5 were generally similar in both summer and winter. However, an increasing trend with higher concentrations of NO3, SO4 and NH4 was observed at Komae on July 28-29. In summer, particulate NO3 was low concentration whereas gaseous NO3 obviously increased in daytime and decreased in nighttime. The ratios of gaseous to total NO3 in nighttime were &gt;0.6 at Komae and almost zero at Maebashi probably due to temperature and humidity. In winter, the ratios of gaseous to total NO3 were much lower than in summer. SO4 generally indicated similar variations spatially and temporally in both summer and winter. Periodical variations of EC and OC were observed in summer, whereas

Currently, about 50% of the world’s population is living in urban areas, and that figure is predicted to continue to increase (United Nations, Department of Economic and Social Affairs Population Division, Population Estimates and Projections Section (2009) World urbanization prospects: the 2009 revision). On the other hand, many cities are facing problems caused by urbanization. The urban heat island phenomenon, one of the urban climate problems, is a typical environmental problem encountered in dense urban areas in summer. The use of the sea breeze to mitigate the urban heat island phenomenon has attracted attention in coastal cities. Some statistics show that about 40% of the world’s population lives within 100 km of the coast (World Resources Institute, Fisheries (2007) Population within 100 km of coast). Further investigation of the environment in the urban area near the coast is, therefore, important. In this chapter, Tokyo is targeted for investigation. Tokyo is the Japanese capital, and its surrounding region, the Tokyo metropolitan area, comprises a circular area with a radius of 50 km and a population of over 30 million. Within this area, the sea breeze from Tokyo Bay is an important factor mitigating the air temperature rise in summer. However, ongoing urbanization could be changing not only the mechanism of the energy balance on the urban surface but also the sea breeze system in the region. To clarify the effects of urbanization, a mesoscale meteorological model was adopted for analysis. Simulation results suggest that expansion of the Tokyo metropolitan area from the 1970s to the 1990s has induced a temperature rise near the ground and that the difference is largest in inland areas. Moreover, the time of sea breeze penetration is delayed in suburban areas. These results suggest that the ongoing urbanization process could raise the air temperature and change the sea breeze system in the Tokyo metropolitan area.

The Central Research Institute of Electric Power Industry (CRIEPI) constructed a nationwide monitoring network to survey acidic deposition in Japan in October 1987. Although the monitoring network was closed in September 1996, monitoring at Komae, Tokyo has been continued over than last two decades. On the basis of the monitoring data collected between October 1987 and September 2010, we analyzed (i) long term trend in the chemical composition of precipitation, (ii) effect of precipitation amounts on the seasonal variation of concentrations, and (iii) influence of changes in precursor′s emissions on precipitation quality in the metropolitan area.&lt;BR&gt;The equivalent ratio of non sea-salt sulfate to nitrate in precipitation significantly increased by 88% during the period from 1987 to 1999, suddenly decreased in the summer of 2000, and did not change during the period from 2002 to 2010. The equivalent ratio of sulfate, nitrate, and chloride to total non sea-salt anion were 31: 53: 16 for the end of 1980′s, 48: 44: 8 for the end of 1990′s, and 40: 56: 4 for the end of 2000′s, respectively. There was a strong effect of precipitation amounts on monthly concentrations of sulfate and nitrate in the warm season. Eruption of Miyake-jima volcano impacted concentrations of sulfate and chloride during the period from 2000 to 2001. The decrease in the concentration of chloride was considered to be related the reduction in hydrochloric acid emissions from industrial waste incinerators in the metropolitan area.

In order to understand the source apportionment of carbonaceous aerosols using a receptor model, we examined the source contribution of fine particles. The observation was done in the summer of 2007 at Maebashi and Kisai. Samples were collected every 6 hours (during the daytime) and 12 hours (during the nighttime), and the following chemical components were analyzed: carbonaceous compounds, ionic components, inorganic elements and radiocarbon content. The Chemical Mass Balance (CMB) method was applied to these data to estimate the source contribution into 10 sources. The carbonaceous compounds were apportioned into the 10 sources using these results, and elemental carbon (EC) was almost entirely diesel-exhaust derived. On the other hand, there was limited primary particle contribution in the organic carbon (OC), and it was estimated as either unknown or secondary particles. The EC and OC were divided into fossil-fuel-derived carbon and biogenic-derived carbon based on the value of the pMC (percent modern carbon) of individual sources derived from the literature. For the secondary organic carbon (SOC), it was found that although the ratio of the fossil-fuel-derived carbon to the biogenic-derived carbon was around 1:2 during the daytime, the fossil-fuel-derived carbon transported from metropolitan area decreased and the ratio dropped to 1:10 during the nighttime, and the observed pMC of total carbon (=EC+OC) increased. As the biogenic-derived-carbon accounted for 70 % of the SOC during the daytime, it was shown that biogenic-derived-carbon provided the major contributions to the SOC.

We investigated the influence of meteorological factors that affect ozone in summer using both measurement analysis and numerical simulation. The results show that there is a close relationship between changes in meteorological conditions and variations in ozone concentrations over the central Kanto area. In summer, up to 84% of long-term variations in peak ozone concentrations may be accounted for by changes in the seasonally averaged daily maximum temperatures and seasonally averaged wind speeds. The ozone episodes in the Kanto region are dominated by three major patterns, of which Patterns I and II are regular summertime pressure patterns with a 26% and 16% frequency of occurrence, respectively. A detailed process analysis of ozone formation under urban heat island (UHI) at two areas in the Kanto region - urban and rural area - indicates that ozone formation is mainly controlled by chemistry, dry deposition, vertical transport, and horizontal transport processes. The ground-level ozone concentrations are enhanced mainly by the vertical mixing of ozone - rich air from aloft, whereas dry deposition process mainly depletes ozone. Horizontal transport and chemistry processes play opposite roles in the net change of ozone concentration between the two areas. The results of numerical simulations also indicate that the sea breeze has significant effects on the ozone accumulation and distribution in the Kanto area. The high ozone was first observed in urban area and then was transported to the rural area by sea breeze. At rural area, the highest ozone concentrations were found in late afternoon, about two hours later in comparison with the urban area. (C) 2009 Published by Elsevier BV

We assessed the ability of the MM5/CMAQ model to predict ozone (O-3) air quality over the Kanto area and to investigate the factors that affect simulation of O-3. We find that the coupled MM5/CMAQ model is a useful tool for the analysis of urban environmental problems. The simulation results were compared with observational data and were found to accurately replicate most of the important observed characteristics. The initial and boundary conditions were found to have a significant effect on simulated O-3 concentrations. The results show that on hot and dry days with high O-3 concentration, the CMAQ model provides a poor simulation of O-3 maxima when using initial and boundary conditions derived from the CMAQ default data. The simulation of peak O-3 concentrations is improved with the JCAP initial and boundary conditions. On mild days, the default CMAQ initial and boundary conditions provide a more realistic simulation. Meteorological conditions also have a strong impact on the simulated distribution and accumulation of O-3 concentrations in this area. Low O-3 concentrations are simulated during mild weather conditions, and high concentrations are predicted during hot and dry weather. By investigating the effects of different meteorological conditions on each model process, we find that advection and diffusion differ the most between the two meteorological regimes. Thus, differences in the winds that govern the transport of O-3 and its precursors are likely the most important meteorological drivers of ozone concentration over the central Kanto area.

We have assessed the contributions of individual physical and chemical atmospheric processes on ozone formation under different weather conditions during a typical summer month (August 2005) using the MM5/CMAQ modelling system. We found that the ozone episodes in the Kanto region are dominated by three major patterns, of which Patterns land II are regular summertime pressure patterns with a 26% and 16% frequency of occurrence, respectively. A process analysis at two typical sites in the Kanto region - one located in the central region of Tokyo and the other located in the rural areas of Kanto - indicates that ozone formation is mainly controlled by advection, vertical diffusion, dry deposition, and chemical processes. The ground-level ozone concentrations are enhanced mainly by the vertical mixing of ozone-rich air from aloft, whereas the dry deposition and chemical processes mainly deplete ozone. By investigating the effects of each process under different weather conditions, we found that the significant decrease in ozone removal due to the chemical and advection processes under conditions of high stagnation is the most important cause of the enhanced levels of ozone in the central region of Tokyo. The results of this study can contribute to a better understanding of ozone formation in the Kanto region, and they may be valuable for local policy makers for further development planning. (C) 2010 Elsevier Ltd. All rights reserved.

The inter-comparison of chemical transport models (CTMs) of four research groups was conducted for O&lt;SUB&gt;3&lt;/SUB&gt; and PM&lt;SUB&gt;2.5&lt;/SUB&gt; simulations in the Kanto area in summer 2007. Three groups used CMAQ v4.6 and the other employed CMAQ v4.5; each group used different emissions data. The results clearly showed that all the CTMs reproduced well the temporal variation of O&lt;SUB&gt;3&lt;/SUB&gt; (r &gt; 0.5 at all four sites), but all the CTMs underestimated PM&lt;SUB&gt;2.5&lt;/SUB&gt; concentrations and did not reproduce the PM&lt;SUB&gt;2.5&lt;/SUB&gt; temporal variation (r &lt;0.5) at suburban sites. Among the PM&lt;SUB&gt;2.5&lt;/SUB&gt; species, the concentration and temporal variation of SO&lt;SUB&gt;4&lt;/SUB&gt;2&lt;SUP&gt;-&lt;/SUP&gt; was predicted well by all the CTMs (within a factor of 2 and r &gt; 0.5 in most cases). By contrast, the elemental carbon (EC) and organic aerosol (OA) concentrations were underestimated by all the CTMs. The predicted NO&lt;SUB&gt;3&lt;/SUB&gt;&lt;SUP&gt;-&lt;/SUP&gt; concentrations showed a high variability (up to a factor of 10) among the four CTMs. Differences in the predicted concentrations of the primary products were explained well by the differences in their emission rates. However, differences in the secondary products, including O&lt;SUB&gt;3&lt;/SUB&gt;, TNO&lt;SUB&gt;3&lt;/SUB&gt; (= HNO&lt;SUB&gt;3&lt;/SUB&gt;+ NO&lt;SUB&gt;3&lt;/SUB&gt;&lt;SUP&gt;-&lt;/SUP&gt;), and the secondary organic aerosols, were not explained by the differences in the precursors&#039; emission rates or in boundary conditions.

Inter-comparison of chemical transport models (CTMs) was conducted among four modeling research groups. Model performance of the ensemble approach to O3 and PM2.5 simulation was evaluated by using observational data with a time resolution of 1 or 6 hours at four sites in the Kanto area, Japan, in summer 2007. All groups applied the Community Multiscale Air Quality model. The ensemble average of the four CTMs reproduced well the temporal variation of O3 (r=0.65-0.85) and the daily maximum O3 concentration within a factor of 1.3. By contrast, it underestimated PM2.5 concentrations by a factor of 1.4-2, and did not reproduce the PM2.5 temporal variation at two suburban sites (r=~0.2). The ensemble average improved the simulation of SO4 2-, NO3 -, and NH4 +, whose production pathways are well known. In particular, the ensemble approach effectively simulated NO3 -, despite the large variability among CTMs (up to a factor of 10). However, the ensemble average did not improve the simulation of organic aerosols (OAs), underestimating their concentrations by a factor of 5. The contribution of OAs to PM2.5 (36-39%) was large, so improvement of the OA simulation model is essential to improve the PM2.5 simulation.

An increasing trend in ground-level ozone (O-3) concentrations has recently been recognized in Japan, although concentrations of ozone precursors, nitrogen oxides (NOx), volatile organic compounds (VOCs) and nonmethane hydrocarbons (NMHCs) have decreased. In this paper, the relationship between meteorological factors (temperature and wind speed) and ground-level ozone concentrations in the summer over the central Kanto area of Japan was examined using both statistical analyses and numerical models. The Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) and the Community Multiscale Air Quality (CMAQ) model were employed in this study. It was found that there is a close relationship between meteorological conditions and ground-level ozone concentrations over the central Kanto area. In summer, up to 84% of the long-term variation in peak ozone concentrations may be accounted for by changes in the seasonally averaged daily maximum temperature and seasonally averaged wind speed, while about 70% of the recent short-term variation in peak ozone depends on the daily maximum temperature and the daily averaged wind speed. The results of numerical simulations also indicate that urban heat island (UHI) phenomena can play an important role in the formation of high ozone concentrations in this area.

&nbsp;&nbsp;&nbsp;In recent years, the urban atmospheric pollution is still an important environmental problem due to the rapid urbanization and industrial development. It is found that atmospheric pollutant concentration can be strongly affected by some local climatic factors (e.g., temperature, humidity, wind, radiation, etc.). In this study, we use the MM5/CMAQ model to examine relationship between these climatic factors and ground ozone (O₃) concentration over Kanto (Japan) area. The nested grid system which cover a region of Kanto with grid resolutions of 9 km, 3 km, and 1 km respectively, have been employed to this study. The relationship between the simulated O₃ concentration with temperature, solar radiation, relative humidity, and wind were analyzed over the August 2005, representing typical summer climate. The numerical simulation shows O₃ concentration as function of temperature, solar radiation, relative humidity and wind direction. The positive correlation was found between O₃ concentration with temperature and solar radiation, while the negative correlation was found between O₃ concentration and relative humidity. The result of this study suggests that O₃ concentration has a close relationship with climatic factors over Kanto area.

Results from the Model Intercomparison Study Asia Phase II (MICS-Asia II) are presented. Nine different regional modeling groups simulated chemistry and transport of ozone (O-3), secondary aerosol, acid deposition, and associated precursors, using common emissions and boundary conditions derived from a global model. Four-month-long periods, representing 2 years and three seasons (i.e., March, July, and December in 2001, and March in 2002), are analyzed. New observational data, obtained under the EANET (the Acid Deposition Monitoring Network in East Asia) monitoring program, were made available for this study, and these data provide a regional database to compare with model simulations. The analysis focused around seven subject areas: O-3 and related precursors, aerosols, acid deposition, global inflow of pollutants and precursor to Asia, model sensitivities to aerosol parameterization, analysis of emission fields, and detailed analyses of individual models, each of which is presented in a companion paper in this issue of Atmospheric Environment. This overview discusses the major findings of the study, as well as information on common emissions, meteorological conditions, and observations. (C) 2007 Elsevier Ltd. All rights reserved.

Eight chemical transport models participate in a model intercomparison study for East Asia, MICS-Asia II. This paper analyzes calculated results for particulate matter of sulfate, nitrate and ammonium through comparisons with each other and with monthly measurements at EANET (the acid deposition monitoring network in East Asia) and daily measurements at Fukue, Japan.
To the EANET measurements, model ensemble means better agree with model individual results for sulfate and total ammonium, although total nitrate is consistently and considerably underestimated. To measurements at Fukue, the models show better agreement than for the EANET measurements. This is likely because Fukue is centered in many of the model domains, whereas the EANET stations are mostly in Southeast Asia and Russia. Moreover, it would be important that Fukue is in Northeast Asia, where the emission inventory is more reliable than Southeast Asia.
The model-model comparisons are made in view of the total amount in the atmosphere, vertical profile, coefficient of variation in surface concentrations, and transformation changes with distance. All the models show reasonable tendencies in vertical profiles and composition ratios. However, total amounts in the atmosphere are discrepant among the models. The consistency of the total amount in the atmosphere would influence source-receptor analysis. It seems that model results would be consistent, if the models take into account the primitive processes like emission, advection/diffusion, chemical transformation and dry/wet deposition, no matter the processes are modeled simply or comprehensively.
Through the comparison study, we learned that it would be difficult to find any problems from one comparison (model-observation comparison with one data or many but at one station or in a short period). Modelers tend to examine model performances only from model-observation comparisons. However, taking budget in a certain or whole model domain would be important, before the models are applied to source-receptor analysis. (C) 2007 Elsevier Ltd. All rights reserved.

Eight regional Eulerian chemical transport models (CTMs) are compared with each other and with an extensive set of observations including ground-level concentrations from EANET, ozone soundings from JMA and vertical profiles from the TRACE-P experiment to evaluate the models' abilities in simulating O(3) and relevant species (SO(2), NO, NO(2), HNO(3) and PAN) in the troposphere of East Asia and to look for similarities and differences among model performances. Statistical analysis is conducted to help estimate the consistency and discrepancy between model simulation and observation in terms of various species, seasons, locations, as well as attitude ranges. In general, all models show a good skill of simulating SO(2) for both ground level and the lower troposphere, although two of the eight models systematically overpredict SO(2) concentration. The model skills for O(3) vary largely with region and season. For ground-level O(3), model results are best correlated with observations in July 2001. Comparing with O(3) soundings measured in the afternoon reveals the best consistency among models in March 2001 and the largest disparity in O(3) magnitude in July 2001, although most models produce the best correlation in July as well. In terms of the statistics for the four flights of TRACE-P experiment, most models appear to be able to accurately capture the variability in the lower troposphere. The model performances for NO(x) are relatively poor, with lower correlation and with almost all models tending to underpredict NO(x) levels, due to larger uncertainties in either emission estimates or complex chemical mechanism represented. All models exhibit larger RMSE at altitudes &lt; 2 km than 2-5.5 kin, mainly due to a consistent tendency of these models towards underprediction of the magnitude of intense plumes that often originate from near surface. Relatively lower correlation at altitudes 2-5.5 km may be attributed to the models' limitation in representing convection or potential chemical processes. Most of the key features in species distribution have been consistently reproduced by the participating models, such as the O(3) enhancement in the western Pacific Ocean in March and in northeast Asia in July, respectively, although the absolute model values may differ considerably from each other. Large differences are found among models in the southern parts of the domain for all the four periods, including southern China and northern parts of some Southeast Asia countries where the behaviors of chemical components and the ability of these models are still not clearly known because of a lack of observational databases. (C) 2007 Elsevier Ltd. All rights reserved.

This paper focuses on the comparison of chemical deposition of eight regional chemical models used in Model Inter-Comparison Study for Asia (MICS-Asia) II. Monthly-mean depositions of chemical species simulated by these models, including dry deposition of SO(2), HNO(3), NH(3), Sulfate, nitrate and ammonium and wet deposition of SO(4)(2-), NO(3)(-) and NH(4)(+), have been provided for four periods (March, July, December 2001 and March 2002) in this work. Observations at 37 sites of the Acid Deposition Monitoring Network in East Asia (EANET) are compared with SO(4)(2-), NO(3)(-) and NH(4)(+) wet deposition model results. Significant correlations appeared between the observation and computed ensemble mean of participant models. Also, differences among modeled sulfur and nitrogen dry depositions have been studied at the EANET sites. Based on the analysis of acid deposition for various species from different models, total depositions of sulfur (SO(2) and sulfate) and nitrogen (nitrate and ammonium) have been evaluated as the ensemble mean of the eight models. In general, all models capture the observed spatial distribution' of sulfur and nitrogen deposition, although the absolute values may differ from measurements. High deposition often occurs in eastern China, Japan, the Republic of Korea, Thailand, Vietnam, Philippines and other parts of Southeast Asia. The magnitude of model bias is quite large for many of the models. In examining the reasons for model-measurement disagreement, we find that differences in chemical processes, deposition parameterization, and modeled precipitation are the main reasons for large model disparities. (C) 2008 Elsevier Ltd. All rights reserved.

This study quantifies the seasonality and geographic variability of global pollutant inflow to Asia. Asia is often looked to as a major source of intercontinental air pollution transport with rising emissions and efficient pollutant export processes. However, the degree to which foreign emissions have been imported to Asia has not been thoroughly examined. The Model Inter-Comparison Study for Asia (MICS-Asia) is an international collaboration to study air pollution transport and chemistry in Asia. Using the global atmospheric chemistry Model of Ozone and Related Tracers (MOZART v. 2.4), and comparing results with a suite of regional models participating in MICS-Asia, we find that imported O-3 contributes significantly throughout Asia. The choice of upper boundary condition is found to be particularly important for O-3, even for surface concentrations. Both North America and Europe contribute to ground-level O-3 concentrations throughout the region, though the seasonality of these two sources varies. North American contributions peak at over 10% of monthly mean O-3 during winter months in East Asia, compared to Europe's spring- and autumn-maxima (5-8%). In comparison to observed data from the Acid Deposition Monitoring Network in East Asia (EANET), MOZART concentrations for 03 generally fall within the range of the MICS models, but MOZART is unable to capture the fine spatial variability of shorter-lived species as well as the regional models. (C) 2007 Elsevier Ltd. All rights reserved.

In the framework of the model intercomparison study-Asia Phase II (MICS2), where eight models are compared over East Asia, this paper studies the influence of different parameterizations used in the aerosol module on the aerosol concentrations of sulfate and nitrate in PM10.
An intracomparison of aerosol concentrations is done for March 2001 using different configurations of the aerosol module of one of the model used for the intercomparison. Single modifications of a reference setup for model configurations are performed and compared to a reference case. These modifications concern the size distribution, i.e. the number of sections, and physical processes, i.e. coagulation, condensation/evaporation, cloud chemistry, heterogeneous reactions and sea-salt emissions.
Comparing monthly averaged concentrations at different stations, the importance of each parameterization is first assessed. It is found that sulfate concentrations are little sensitive to sea-salt emissions and to whether condensation is computed dynamically or by assuming thermodynamic equilibrium. Nitrate concentrations are little sensitive to cloud chemistry. However, a very high sensitivity to heterogeneous reactions is observed.
Thereafter, the variability of the aerosol concentrations to the use of different chemistry transport models (CTMs) and the variability to the use of different parameterizations in the aerosol module are compared. For sulfate, the variability to the use of different parameterizations in the aerosol module is lower than the variability to the use of different CTMs. However, for nitrate, for monthly averaged concentrations averaged over four stations, these two variabilities have the same order of magnitude. (C) 2007 Elsevier Ltd. All rights reserved.

This paper studies two high-pollution episodes over Greater Tokyo: 9 and 10 December 1999 and 31 July and 1 August 2001. Results obtained with the chemistry transport model (CTM) Polair3D are compared to measurements of inorganic particulate matter (PM&lt
inf&gt
2.5&lt
/inf&gt
). To understand to which extent the aerosol processes modeled in Polair3D impact simulated inorganic PM&lt
inf&gt
2.5&lt
/inf&gt
, Polair3D is run with different options in the aerosol module, i.e., with/without heterogeneous reactions. To quantify the impact of processes outside the aerosol module, simulations are also done with another CTM (community multiscale air quality, CMAQ). In the winter episode, sulfate is mostly impacted by condensation, coagulation, long-range transport, and deposition to a lesser extent. In the summer episode, the effect of long-range transport largely dominates. The impact of condensation /evaporation is dominant for ammonium, nitrate, and chloride in both episodes. However, the impact of the thermodynamic equilibrium assumption is limited. The impact of heterogeneous reactions is large for nitrate and ammonium and, taking heterogeneous reactions into account, appears to be crucial in predicting the peaks of nitrate and ammonium. The impact of deposition is the same for all inorganic PM&lt
inf&gt
2.5&lt
/inf&gt
. It is small compared to the impact of other processes although it is not negligible. The impact of nucleation is negligible in the summer episode and small in the winter episode. The impact of coagulation is larger in the winter episode than in the summer episode because the number of small particles is higher in the winter episode as a consequence of nucleation. Copyright 2007 by the American Geophysical Union.

[1] This paper studies two high-pollution episodes over Greater Tokyo: 9 and 10 December 1999 and 31 July and 1 August 2001. Results obtained with the chemistry transport model (CTM) Polair3D are compared to measurements of inorganic particulate matter (PM2.5).To understand to which extent the aerosol processes modeled in Polair3D impact simulated inorganic PM2.5, Polair3D is run with different options in the aerosol module, i.e., with/without heterogeneous reactions. To quantify the impact of processes outside the aerosol module, simulations are also done with another CTM (community multiscale air quality, CMAQ). In the winter episode, sulfate is mostly impacted by condensation, coagulation, long-range transport, and deposition to a lesser extent. In the summer episode, the effect of long-range transport largely dominates. The impact of condensation/evaporation is dominant for ammonium, nitrate, and chloride in both episodes. However, the impact of the thermodynamic equilibrium assumption is limited. The impact of heterogeneous reactions is large for nitrate and ammonium and, taking heterogeneous reactions into account, appears to be crucial in predicting the peaks of nitrate and ammonium. The impact of deposition is the same for all inorganic PM2.5. It is small compared to the impact of other processes although it is not negligible. The impact of nucleation is negligible in the summer episode and small in the winter episode. The impact of coagulation is larger in the winter episode than in the summer episode because the number of small particles is higher in the winter episode as a consequence of nucleation.

The relationships between changes in secondary inorganic aerosol concentrations (SIA) and emission reductions in Greater Tokyo were investigated through numerical simulations. First of all, it was confirmed that the numerical model used in the simulations showed an acceptable performance in reproducing measurements. It was shown by analyzing the simulated results that both annual mean concentrations and high-episodic daily concentrations decreased with reduced emissions. The reduction of SIA concentrations appeared mostly in summertime, but the concentrations in wintertime increased with decreasing emissions in some cases. These changes in the SIA concentrations largely depended on the changes in nitrate concentrations.

We evaluated the performance of the newly developed atmospheric mesoscale model, WRF, for the simulation of urban-scale weather in the Tokyo metropolitan area during a high photochemical Oxidant event. The simulation clearly shows that WRF represents the spatial distribution of surface air temperature during the daytime, although the model temperature is lower than the observations in the late afternoon to evening in the urban area. The wind system can be well reproduced in WRF. Simulated convergence zone moves toward the inland areas located to the northwest of the coastal area during the three hours. These results are consistent with the observations of temperature and Photochemical Oxidant, indicating that WRF has enough potential to predict the ongoing Oxidant concentration.

This paper presents a modal aerosol model (MAM) developed to be used in three dimensional air quality models. MAM, which represents the aerosol distribution with four modes, has the advantage of simplicity and speed efficiency associated to modal models, while mass transfer is modeled with a dynamic approach. To assess the ability of MAM to represent mass transfer, MAM is compared to a size-resolved model based on the dynamic approach and to a version of MAM based on an equilibrium approach. Comparisons are done using measurements of inorganic species made in Japan as initial conditions. Furthermore, it is shown that MAM combined with a well chosen mode splitting scheme is able to deal accurately with the simultaneous occurrence of strong nucleation/condensation and coagulation, as may be observed in high nucleation episodes.

In order to obtain information on the vertical distributionof ozone concentration in the lower atmosphere, field experiments were conducted at Mt. Fuji located on the prefecture boundary of Shizuoka and Yamanashi. The ozone concentration was monitored by Ogawa passive samplers at 20points from base to top of Mt. Fuji during the period from 12 to 20 July, 2005. The temporal variation of ozone concentration was also analyzed by the automatic monitoring data at three urban points on the base of Mt. Fuji and the top of Tanzawa about 30 km East from Mt. Fuji.&lt;BR&gt;The estimated average ozone concentrations were about 20 ppbv for the mixing layer and about 40 ppbv for the free atmosphere; these values agreed with the recently reported values observed at mountainous areas in the summer season. The estimated average ozone concentrations were about 20 ppbv for three urban points and about 40 ppbv for the top of Tanzawa, with a significant diurnal variation. It was considered that the mid-slop of Mt. Fuji was influenced by local air pollution occasionally depending on the meteorological condition.&lt;BR&gt;The passive sampler would be useful by coupling an UV-photometric monitor to analyze the transport of ozone and oxidant in the lower atmosphere.

Concentrations of PM_2.5 mass and inorganic ionic components measured in Komae, Tokyo, from FY1998 to FY2005 are analyzed for studying the interannual variability. It is found that the mass concentration tends to decrease annually, and this tendency is pronounced in winter. It is considered from the comparisons with other studies in South Kanto that the decreasing tendency is a relatively large-scale phenomenon, and the PM_2.5 mass concentration is being uniformed in the area.<BR> Inorganic ionic species do not show such decreasing tendency in general. As a result, concentration ratios of secondary inorganic aerosol (SIA) to PM_2.5 mass tend to increase. This could lead to the uniformity in PM_2.5 mass concentration. The SIA concentration is high, very close to the US Air Quality Standard for PM_2.5. Therefore, the SIA should be more concerned in order to reduce the PM_2.5 mass concentration.

The denuder/filter-pack sampling system has been used to simultaneously measure the daily concentrations of inorganic compounds of fine and coarse aerosol and related gases in Fukue Island, Japan, in three springs (March-April of 2000-2002). Gaseous nitric acid concentrations are low, and gas-to-total (gas + aerosol) fractions of nitrate are also low. The gas-to-total fraction of ammonium and the production of non-sea-salt (nss)-sulfate on coarse aerosol increase with dust loading. Total nitrate concentration correlates with both total ammonium concentration and total aerosol nss-sulfate concentration, although these species are differently partitioned among the gas and fine- and coarse-aerosol phases. In some dust events, there is a time lag between an increase in nss-sulfate concentration and an increase in dust loading. Trajectory analysis shows that one of the dust events with a time lag is composed of nss-sulfate from the east affected by volcanic plumes and dust from the northwest passing over the loess areas in the Asian continent. &COPY; 2005 Elsevier Ltd. All rights reserved.

Europe has already established tentative critical levels of air pollutants based on the dose responses. Current ozone level has the potential adverse impact to plants. However, the relation with air pollutants is not clarified. The purpose of this study make GIS database to evaluate the relationship between air pollutants and forest decline, quantitatively and visually, and proposes critical level mapping method. The observation data, such as the forest decline monitoring data, the long term monitoring data of air pollutants and the meteorology data was collected. Geostatistical analysis (kriging method) was applied for making oxidant based accumulated exposure Over a Threshold of 40 ppb (A0T40) map from 1975 to 2001. And, the relation between air pollutants and Red pine, Larch, and Beech forest decline was analyzed using GIS database. Trials to present excess maps of pollutants would help a risk assessment of the impacts on forests health using critical levels evaluated by exposure experiments. AOT40 seemed to be effective as an index of the vegetation influence evaluation.

Measurable spectral regions of the open light path spectrometer developed by CRIEPI contain absorption bands of volatile organic compounds (VOC) which deeply relate to the formation of SPM that influences human health. In the report, we concentrated on the retrieval of 7 species of VOC, ozone, and sulfur dioxide. In the retrieval procedures, gas concentrations were determined by correlated linear least-squares fit, and a correction for the oxygen absorption structure was added to ensure higher accuracy of the retrieval results. For the evaluation of the retrieved concentrations, comparisons were carried out with gas concentrations that were simultaneously measured from directly trapped atmosphere. The results of the comparisons showed good correlations for all species excepting one VOC that existed as an undetectable concentration between the measurement periods. Furthermore, time variations of the retrieved VOC concentrations corresponded with those of the nitrogen oxide concentration of mobile exhaust emission are most likely the largest contributor.

In Japan, the nation-wide annual-mean concentration of suspended particulate matter (SPM) dramatically decreased, and the achievement rate of the air quality standard of SPM was considerably improved in FY1999. This study shows the actual conditions and meteorological causes of the low concentration. The nation-wide monthlymean concentration of SPM was low in April, from June to August, and in February in FY 1999. In July and August, the SPM concentration was remarkably low in Kanto, where the SPM concentration was characterized with very low concentrations continuing for as long as a week or more. Meteorological factors were analyzed for the low concentrations in Kanto in July and August, 1999. On a monthly basis, these two months of 1999 were characterized by stronger wind speeds and more precipitation than the five years around 1999, which could be causes of the low concentration. In the very low concentration weeks, however, such low concentrations were related to the mostly constant wind direction, which brought maritime air from the Pacific Ocean.

To evaluate the primary factor for the seasonal variation and the level of atmospheric ammonia concentration in the local scale, the emission, transport, and deposition of atmospheric ammonia were analyzed in the Kanto region of Japan, which has an area of about 40,000 km(2), by means of an atmospheric transport model. In the analysis of episodes of high concentration, the model reproduced an observed concentration of NH3 and NH4+ particles during a 5-day 4 observation period in the summer of 2002. In the annual simulation, the calculated concentration showed reasonable agreement with the spatial distribution and seasonal variation of the annual observation in 2000. The NH3 concentration strongly reflected the effect of local emission sources because of its short lifespan in the atmosphere. Moreover, it is found from the simulation results that atmospheric ammonia was transported over long distances when it existed as a particulate. The calculated deposition amount of NH3 and NH4+ particles was about the same as the emission amount of NH3 throughout the year. Moreover, the model simulation showed that there was little contribution from sources outside the Kanto region. These findings suggest that the concentration and the deposition in the Kanto region mainly originated from the emission sources in itself. (C) 2004 Elsevier Ltd. All rights reserved.

ABSTRACT; Europe has already established tentative critical levels of air pollutants based on the dose responses, however, not yet in the Asia. The critical levels are becoming needed for evaluating plant responses to air pollutants in the East Asia. Current ozone level has the potential adverse impact to plants. On the other hand, Forestry Agency in Japan carried out forest health monitoring survey. However, the relation with air pollutants is not clarified. This study analyzed observation data by using GIS to evaluate the relationship between air pollutants and decline, quantitatively and visually. Study areas are Sugi (Cryptomeria japonica D. Don) forests in the Kanto plains, where many surveys and reports have been done. Geostatistical analysis (kriging method) was applied for making oxidant based AOT40 (Ox) map in the forest monitoring period of Forestry Agency. The distribution and range of AOT40 (Ox) were compared with daytime and nighttime, and different monitoring period. Furthermore, AOT40 (0x) values were extracted and analyzed at each monitoring point, to examine the relationship between the mean decline index and climate normals (ATP, Precipitation index) or land use (e. g. forest rate).

The denuder/filter-pack sampling system has been used for three years since September 1998, in order to measure daily concentrations of nitrate, chloride and ammonium in the gas and fine-and coarse-aerosol phases in Tokyo.&lt;BR&gt;Total nitrate concentration does not vary seasonally, but its partitioning ratio shows remarkable seasonality with increases in the gas phase in summertime and in the fine-aerosol phase in wintertime. Total chloride concentration is high in wintertime due to non-sea-salt chloride in the fine-aerosol phase. Total ammonium concentration varies a little with season as well as its partitioning ratio.&lt;BR&gt;Those measurements are analyzed for the partitioning of nitrate, ammonium and chloride between the gas and fine-aerosol phases. It was found that estimates based on equilibrium reactions in a multi-component system are very comparable to measured concentration products of gaseous components. This suggests that the gaseous components are in equilibrium with corresponding components in internally-mixed fine aerosol. In wintertime, however, the concentration products are also well predicted by equilibrium coefficients in a single component system, which implies that external mixture of fine aerosol can be applied.

An analytical procedure to which the multiderivatives of the atmospheric absorption spectrum and of absorption cross section spectra are applied has been proposed in order to retrieve atmospheric constituent concentrations. In this study, the proposed method was evaluated by applying it to real atmospheric absorption spectra. Preceding the evaluation, an open light path spectrometer for acquiring atmospheric absorption spectra was developed. The instrument consisted of an artificial light source, a telescope for both emitting and receiving light, a reflector, and a spectrometer. Absorption spectra can be acquired in the spectral region from UV to visible. The instrument can achieve a high signal to noise ratio and high-speed sampling because it is equipped with a two-dimensional CCD detector. To evaluate the applicability of the proposed procedure, measurements of concentrations of NO&lt;SUB&gt;2&lt;/SUB&gt;, O&lt;SUB&gt;3&lt;/SUB&gt;, SO&lt;SUB&gt;2&lt;/SUB&gt;, and HCHO were carried out together with other instruments. The results of the comparisons showed good agreement for all species.

The emission strength of ammonia based on the volatilization generally increases as the temperature rises. Thus, the concentration of NH3 in the atmosphere is higher in summer, and the peak tends to appear in the daytime. However, in observations of atmospheric ammonia in summer 2002, although a high concentration of NH3 was observed in the daytime at Akagi, which is located in an agricultural area in the northern Kanto region, a high concentration was observed in the nighttime at Kagurazaka, which is located in the Tokyo urban area. This study evaluates the high concentration of NH3 in the nighttime at Kagurazaka by means of modeling analysis. The concentration of NH3 was simulated using Models-3/CMAQ with the meteorological fields of MM5. As a result, the calculated concentrations showed a good agreement with the observed concentrations for each site. The appearance of high concentration of NH3 in the nighttime at Kagurazaka, was consistent with the results of a simulation. (C) 2003 Elsevier Ltd. All rights reserved.

We performed SO2, NO2, and O-3 measurements in the lower troposphere using a multiwavelength differential absorption lidar (MDIAL) system. Measurement results are compared with results of airborne and ground-based in-situ measurements performed simultaneously with lidar measurement. Vertical concentration variation Of SO2 with 0-7 ppb for 1000-1700 in altitude was measured by dual-DIAL, and those of NO2 and O-3 with 0-50 ppb for 700-2000 in altitude were measured by 2-wavelength DIAL quasi-simultaneously. Measurement results suggest that NO2 was trapped below the inversion layer, which induced the reduction of O-3 concentration by the reaction with NOx. Comparison of results obtained by DIAL and by in-situ methods showed that the MDIAL system had sufficient accuracy for verification of long-range transport models of sulfur compounds and for observation of chemical reactions of oxidants and nitrogen oxides. We also performed simultaneous profiling of NO2 and O-3 in the lower troposphere using a stable, high power transmitter for NO2 measurement. Concentration variations of NO2 and O-3 for 900-1350 m altitude were measured for a continuous time interval of 24 hours without maintenance.

Future acidic depositions in Japan were forecasted for various energy consumption and emission control scenarios. In the case of the current legislation scenario and the economic reform scenario, sulfur and nitrogen depositions in Japan would increase by approximately 10-20 percent and 30 percent, respectively, from 1995 to 2030. In the case of the hypothetical worst-case scenario for China, sulfur deposition in several sites, facing the Sea of Japan would double by 2030. It can be deduced that the increase in acidic deposition is mainly due to the increase in emissions of air pollutants in the area surrounding Bo Hai and Huang Hai, which are located west of the Korean Peninsula.

An intercomparison study involving eight long-range transport models for sulfur deposition in East Asia has been initiated, The participating models included Eulerian and Lagrangian frameworks, with a wide variety of vertical resolutions and numerical approaches. Results from this study, in which models used common data sets for emissions, meteorology, and dry, wet and chemical conversion rates, are reported and discussed. Model results for sulfur dioxide and sulfate concentrations, wet deposition amounts, for the period January and May 1993, are compared with observed quantities at 18 surface sites in East Asia. At many sites the ensemble of models is found to have high skill in predicting observed quantities. At other sites all models show poor predictive capabilities. Source-receptor relationships estimated by the models are also compared. The models show a high degree of consistency in identifying the main source-receptor relationships, as well as in the relative contributions of wet/dry pathways for removal. But at some locations estimated deposition amounts can vary by a factor or 5. The influence of model structure and parameters on model performance is discussed. The main factors determining the deposition fields are the emissions and underlying meteorological fields. Model structure in terms of vertical resolution is found to be more important than the parameterizations used for chemical conversion and removal, as these processes are highly coupled and often work in compensating directions. (C) 2002 Elsevier Science Ltd. All rights reserved.

Numerical experiments using a long-rage transport model of suffer compounds were carried out to investigate influences of vertical distribution of sources on deposition fields in East Asia.
Monthly dry depositions of SOx emitted from a source placed at the center of the domain were insensitive to the vertical distribution of the source, with increasing distance from the source. The depositions at the source grid strongly reflected the emission intensity in the lowest layer. The vertical distribution of sources affected the source-receptor relationships at receptors near locally large emissions but not so much at remote receptors. It was presented that long-rage transport was not influenced by the vertical distribution of sources, i.e., far sources may be treated as either area sources or elevated sources.

Wet deposition monitoring was conducted at six rural stations in western Japan, during the period from 1987 through 1996. Long-term trends in the concentration of non-sea salt ions were analyzed on the basis of the data obtained. The monitoring results indicated that annual average concentrations of NO3- and NH4+ in precipitation significantly increased on the order of 45%, and that of nss-Ca2+ and nSS-SO42-, concentrations did not change over the past 10 years. The ratio of NO3-/nss-SO42- in precipitation significantly increased, the ratio of NO3-/NH4+ showed no marked fluctuations, and the ratio of [nss-Ca2++NH4+]/[nss-SO42-+NO3-] slightly increased during the period. These findings suggested that the wet deposition of NO3- and NH4+ in western Japan, particularly that in the winter season, was influenced by the long-range transport of nitrogen oxides and ammonia from the Asian continent.

In order to contribute to the analysis and solution of regional scale environmental problems in East Asia, we developed a tool for the comprehensive assessment of alternative policy options to improve air quality. This tool projects the future regional energy supply, calculates the emission levels of sulfur dioxide and estimates the geographical pattern of sulfur deposition resulting from emissions. Sulfur deposition in Japan through 2030 was forecasted for various energy supply and emission control scenarios using the analysis tool. Future sulfur depositions were calculated from the source-receptor matrix for 1995 and the growth rate of emission for the source subregion. In the case of the current legislation scenario, anthropogenic SO2 emissions in East Asia would grow by 34 percent and sulfur deposition in Japan would increase by approximately 20 percent between 1995 and 2030. This increase in sulfur deposition over these 35 years is slightly less than the contribution from volcanic emission to sulfur deposition in Japan. In the case of the hypothetical dirty scenario for China, sulfur deposition in several grids which face the Sea of Japan would double by 2030.

Ammonia emissions are important for the study of atmospheric transport and reaction models, because of their effects on the acidification processes of NO&lt;SUB&gt;x&lt;/SUB&gt; and SO&lt;SUB&gt;x&lt;/SUB&gt; in the atmosphere. Previously no sufficient ammonia emissions data were available for Japan. We have estimated ammonia emissions in Japan during 1994FY and determined their time-space variations. Estimated total ammonia emissions were 0.52 Mt/y, and the greatest contribution, 0.34 Mt/y, was from the agricultural sector, while 0.15 Mt/y was attributed to urban activities. Our estimated molecular ratio of ammonia to NO&lt;SUB&gt;x&lt;/SUB&gt; in total emissions was 0.83, and 2.3 to SO&lt;SUB&gt;x&lt;/SUB&gt;. The fine-spase disaggretion of estimated emissions was shown to be consistent with the NH&lt;SUB&gt;3&lt;/SUB&gt;/NO&lt;SUB&gt;x&lt;/SUB&gt; ratio by comparison with previosly measured total NH&lt;SUB&gt;3&lt;/SUB&gt;/total NO&lt;SUB&gt;x&lt;/SUB&gt; concentration ratio in the atmosphere.

To help improve the use of models in science & policy analysis in Asia it is necessary to have a better understanding of model performance and uncertainties. Towards this goal an intercomparison exercise has been initiated as a collaborative study of scientists interested in long-range transport in East Asia. An overview of this study is presented in this paper. The study consists of a set of prescribed test calculations with carefully controlled experiments. Models used the same domain, emission inventory, model parameters, meteorological conditions, etc. Two periods (January and May 1993) were selected to reflect long-range transport conditions under two distinct seasons. During these periods measurements of sulfur concentrations and deposition were made throughout the study region using identical sampling and analysis protocols. The intercomparison activity consists of four tasks (Blind Test, Fixed Parameter Test, Source Receptor test, and Tuning Test). All participants were asked to do Task A, and as many of the other tasks as possible. To date seven different models have participated in this study. Results and key findings are presented.

A comparison between transport models is done to study the sulfur deposition in East Asia. A single-layer Lagrangian model with simple chemistry is compared to a multilayered 3D Eulerian model. The comparison is done for two-month-long episodes of winter (February) and summer (August) 1989. The model-predicted sulfur deposition is about 0.1 g S (m(2) month)(-1) for regions with the largest emissions. A comparison between the model-predicted and the observed values at a network of monitoring stations in Japan shows similar temporal trends. The sulfur deposition due to volcanic emissions in Japan has been shown to be about 20% of the total deposition in that country.

A long-range transport model for East Asia was developed to estimate the sulfur deposition in Japan. The model is a hybrid type that combines a trajectory model for distant sources with a Eulerian model for nearby sources. The processes of transport and diffusion, chemical reactions, cloud scavenging, transfer of sulfate from cloud water to rainwater, and dry and wet depositions are considered. The emission distribution of sulfur dioxides in East Asia, with approximately 80 km X 80 km resolution, was updated. The emission distribution in Japan on a grid system with resolution in both the horizontal and vertical directions three times higher than that of the grid system for East Asia was also estimated for the Eulerian part of the hybrid model. The important assumption used in the hybrid model is that substances emitted from distant sources are well mixed during the long-range transport and are uniformly distributed in the vertical direction. This assumption was confirmed from the result of airplane measurements in the area of the sea northwest of Kyushu Island in Japan. The results obtained using the hybrid model were evaluated through comparison with observed data of acidic deposition. Observations were conducted at 21 stations throughout Japan during one year. The calculated amount of total sulfur deposition in Japan was 0.43 Tgy(-1) (Tgy(-1) = 10(12) g per year) in sulfur equivalents, while the observed amount was 053 Tgy(-1). The long-range transport model can predict more than 80% of observed sulfur deposition. The tendency of underprediction could be improved by changing the treatment of mass transfer to liquid phases. The sources contributing to the total sulfur deposition in Japan were estimated using the hybrid model. The contributions of Japanese anthropogenic sources. volcanic eruptions, and Asian continental sources were 40%, 20%, and 40%, respectively.

The seasonal variation in measured particulate nitrate at Cheju island, South Korea, is analyzed and shown to exhibit high concentrations from February to June and in October, and low values from July to September. Total nitrate concentrations, which are not monitored, are estimated with a gas-aerosol equilibrium model with two-size bins. The total nitrate concentrations are shown to be maximum in June and minimum in August, and these differences are associated with air-mass trajectories. The fraction of particulate to total nitrate is estimated and shown to be sensitive to the total nitrate concentrations and the coarse-mode composition that is dominated by non-volatile species. The particulate nitrate fractions are found to vary within a relatively narrow range around the annual-mean value, indicating that the particulate nitrate concentrations behave similarly to the total nitrate concentrations. Exceptions are found for April, June and July. For April the largest particulate nitrate fraction is found in association with very high concentrations of nss-calcium, an indicator of mineral aerosol. The smallest particulate nitrate fractions occur in June and July and are the result of a combination of low concentrations of nss-calcium, sea salt and total nitrate, and high concentration of nss-sulfate. (C) 1998 Elsevier Science Ltd. All rights reserved.

Aerosol chemical composition data measured at Cheju Island, Korea from March 1992 to December 1994 are analyzed with a gas-aerosol equilibrium model. The aerosol composition is divided into fine and coarse modes, with each mode assumed to be in equilibrium with the gas phase. The model represents the mean aerosol composition. The particulate ammonium is found to exist mostly in the fine mode to neutralize nss-sulfate, and the particulate nitrate and chloride are present mostly in the coarse mode and compete with each other to share sea salt and mineral cations. This means little formation of ammonium nitrate and chloride. Sensitivity analyses suggest that the aerosol in this region will be more deficit in chloride due to dechlorination and ammonium nitrate associated with the fine mode may become important. (C) 1997 Published by Elsevier Science Ltd.

Thirty-two months of aerosol chemical composition measured at Cheju Island, Korea, are analyzed with a gas-aerosol equilibrium model. The aerosol composition is divided into the fine and coarse sections, with each section assumed to be in equilibrium with the gas phase, which was supported by the calculations. The particulate ammonium is found to exists in the fine section to neutralize nss-sulfate, and the particulate nitrate and chloride is present in the coarse section and competes with each other to share sodium, potassium, calcium, and magnesium.

We have developed a hybrid long-range transport (LRT) model to estimate long-term sulfur deposition amounts in Japan. This model combines a trajectory model for the LRT with an Eulerian model for the short-range transport and deposition. The hybrid model shows the ability to predict concentrations influenced by large nearby sources, which the trajectory model we previously developed consistently underestimated. The hybrid model is designed as an engineering model, which allows for longterm estimation without the requirements of detailed data on meteorology, surface condition, and emission over the whole domain, and huge computer resources required for comprehensive Eulerian models.