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>都心上空での大気質を把握するため、東京スカイツリー(TST)で上空の大気質の定点観測を行ってきた。その中で、2015年12月9～10日には地上で高濃度のPM<sub>2.5</sub>が観測された。この事例に着目し、地上・上空の各種汚染物質の濃度変動から、都心域での地上–上空間における大気質の挙動差、PM<sub>2.5</sub>の高濃度要因を解析した。9日午後の東京スカイツリー高度320m (H320)で地上より高い二酸化硫黄(SO<sub>2</sub>)濃度が観測された。これは9日18時ごろから境界層が形成され、H320は南風により大規模固定煙源や船舶の影響を受け続けたためと思われる。都心付近で微小粒子状物質(PM<sub>2.5</sub>)濃度が90 μg/m<sup>3</sup>を越えた10日夜は、いわゆる房総前線に伴う逆転層の形成が高濃度の原因と考えられた。この高濃度域は東京23区南東部が中心で、高濃度汚染気塊の高さは22～23時で200m程度と推定された。また、両日午前中のH320と地上(H10)の粒子数濃度比(N<sub>H320</sub>/N<sub>H10</sub>)は、粒径が小さいほど早く増加を始める傾向があった。</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>領域化学物質輸送モデルに適用したトレーサー法を用いて、2010年度を対象にわが国の微小粒子状物質(PM_2.5)の発生源寄与を評価した。最新の排出量インベントリや文献等から2010年度を対象とした発生源データを構築した。国内の人為起源発生源を種別に10区分、国外の人為起源発生源を領域別に中国、韓国、その他の領域とし、船舶、自然起源の計15区分を発生源寄与評価の対象とした。月別無機イオン成分濃度、季節別PM_2.5成分濃度、日別PM_2.5濃度の観測データを用い、モデル再現性を統計解析の指標から検証し、発生源寄与評価への適用に十分な再現性を有することを確認した。わが国における発生源寄与評価の結果、年平均の日本全域のPM_2.5濃度に対し、国内の寄与が3.60 μg/m³（相対比で33.9％）と最大で、中国の寄与は3.10 μg/m³（同29.2％）であった。国内の寄与の内訳は自動車（同7.4％）、製造業（同7.0％）、家畜（同5.5％）、その他の国内発生源（同5.4％）、肥料施肥（同2.8％）、以下、電気業、機械、業務、廃棄物処理（同1–2％前後）であった。さらに、長期基準と短期基準の達成・非達成局別に発生源寄与を評価し、非達成の要因を地域別に評価した。九州域においては特に短期基準非達成の要因として国外の強い影響が懸念されること、瀬戸内では製造業と船舶、近畿ではこれに加えて自動車の寄与が大きいこと、関東では短期基準非達成の要因には自動車と製造業の寄与が大きいが、長期基準の点からは自動車が重要な発生源であることなどが明らかとされた。</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;東京都狛江市において、2014年4月から2015年3月までの各月上旬（10日間）にフィルタ法とデニューダ・フィルタ法を用いて微小粒子状物質（PM&lt;sub&gt;2.5&lt;/sub&gt;）を併行採取し、IMPROVEプロトコルに基づく熱分離・光学補正法により有機炭素濃度の測定を行った。その結果、フィルタ法の有機炭素濃度は0.6–8.4 μgC/m&lt;sup&gt;3&lt;/sup&gt; （平均2.8 μgC/m&lt;sup&gt;3&lt;/sup&gt;、標準偏差1.4 μgC/m&lt;sup&gt;3&lt;/sup&gt;）、デニューダ・フィルタ法の有機炭素濃度は0.2–7.6 μgC/m&lt;sup&gt;3&lt;/sup&gt; （平均1.7 μgC/m&lt;sup&gt;3&lt;/sup&gt;、標準偏差1.2 μgC/m&lt;sup&gt;3&lt;/sup&gt;）であった。これらの濃度差より、ガス状有機炭素濃度は0–4.1 μgC/m&lt;sup&gt;3&lt;/sup&gt; （平均1.1 μgC/m&lt;sup&gt;3&lt;/sup&gt;、標準偏差0.9 μgC/m&lt;sup&gt;3&lt;/sup&gt;）と見積もられた。フィルタ法で採取した全有機炭素のうちガス状有機炭素が占める割合（正のアーティファクト）は2014年5月から2015年2月まで0.3–0.4の範囲内にあったが、2014年4月と2015年3月は0.5以上となっていた。これより、春季の有機炭素は半分以上がガス態であり、PM&lt;sub&gt;2.5&lt;/sub&gt;中の有機炭素分析において大きな影響を与えていることが示唆された。また、ガス状有機炭素の60–90％はOC2であり、その濃度は一年を通して大きな変化がなかったことから、大気環境中にはOC2に含まれる成分が一定量存在していることがわかった。一方、粒子状有機炭素はOC3とOCpyroが主成分で50–70％を占めており、特に11月に高くなっていた。&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.

近年、日本国内において、オゾンの前駆物質濃度は減少する傾向にあるがオゾン濃度は長期的なトレンドでは増加している。越境汚染の影響が比較的少ない夏季の関東地方では国内の発生源対策が重要と考えられる。本研究ではWRFおよびCMAQと2000年から2005年にかけての排出量減少を反映した排出量データを用いた大気質シミュレーションを行い，排出量の削減がオゾン濃度に与えた影響を検証した。その結果、2000年から2005年のNO&lt;sub&gt;x&lt;/sub&gt;とVOCの排出量削減により，オゾン日中最高濃度は東京湾沿岸の一部を除いた関東全域で減少を示していた。また、NO&lt;sub&gt;x&lt;/sub&gt;のみ削減した場合、オゾン日中最高濃度は東京都心を中心に増加するが内陸部では減少することが示された。VOCのみの削減では関東の全域で濃度減少が示され、VOC削減の有効性が示唆された。さらに、高濃度日に対する感度解析の結果、内陸部ではNO&lt;sub&gt;x&lt;/sub&gt; sensitive あるいはMixed sensの状態を取る事が多く、一方の都心周辺ではVOC sensitiveの状態が優勢であった。この結果よりそれぞれの地域でのオゾン濃度低減に対する前駆物質の削減の有効性が示された。

微小粒子状物質(PM&lt;sub&gt;2.5&lt;/sub&gt;)の主要成分の1つである非海塩起源硫酸塩(nss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;)について、前駆体である二酸化硫黄(SO&lt;sub&gt;2&lt;/sub&gt;)までを含めて、わが国における国内外の発生源寄与を包括的に評価した。対象とした発生源は中国、韓国、日本の人為起源および火山由来の自然起源である。発生源寄与の季節変動について評価を行うため、2005年1、4、7、10月について、36 kmの水平解像度を有する数値モデルで計算を行い、数値モデルはSO&lt;sub&gt;2&lt;/sub&gt;とnss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;ともに観測値と比較して良好な再現性を有することを確認した。トレーサー法を用いて発生源寄与を推定した結果、わが国においては、SO&lt;sub&gt;2&lt;/sub&gt;は季節を通じて自国の寄与が支配的(各季の平均値で1.00 ppbv、相対比では66.3%)であり、一方でnss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;は季節を通じて中国の寄与が支配的(各季の平均値で2.22 μg/m&lt;sup&gt;3&lt;/sup&gt;、相対比では50.6%)であることが示された。火山由来の自然起源の寄与は、春季と秋季には日本の人為起源の寄与を上回る結果となった。SO&lt;sub&gt;2&lt;/sub&gt;は自国の寄与が支配的であるが、その濃度は桁違いで大陸よりも小さいため、二次生成するnss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;については、夏季には中国でほぼすべて(95%以上)が粒子化したうえで、夏季以外には輸送される過程で粒子化しながら、わが国のnss-SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;濃度に影響を及ぼしていることを明らかとした。

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.

微小粒子状物質(PM&lt;sub&gt;2.5&lt;/sub&gt;)の地上観測と、衛星から観測されるエアロゾル光学的厚さ(AOD)について、10年以上の長期間の観測データを活用して月平均値を基本にその対応関係について解析を行った。各地点の観測データについて、PM&lt;sub&gt;2.5&lt;/sub&gt;とAODは利尻、隠岐、箆岳、川崎の4地点では相関係数0.7程度の有意な相関があり、大阪における相関はやや低めで、また中国北京では有意でない結果を得た。この点に関し、衛星データの月内データカバー率を考慮することが両者の対応関係を適切に評価する上で必要であることを示し、データカバー率が40%以上のデータに対象を限ると、日本の5地点と中国北京の計6地点すべてで有意であり、平均して0.63の相関係数を得た。PM&lt;sub&gt;2.5&lt;/sub&gt;とAODには空間的にも有意な相関があり、AODを活用した一例として、北京をはじめ大陸で非常に高濃度のPM&lt;sub&gt;2.5&lt;/sub&gt;が観測された2013年1月の事例について2001年から2010年までの10年平均値との偏差を解析した。その結果、日本域におけるPM&lt;sub&gt;2.5&lt;/sub&gt;の顕著な増加は見られなかったことがAODの解析結果から示された。衛星から観測されるAODはPM&lt;sub&gt;2.5&lt;/sub&gt;の動態解析に用いることができる有用な情報の一つであることを示した。

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.

近年、日本国内においてオゾンの高濃度化、出現頻度の増加が社会問題となっている。夏季の関東地方内陸部における高濃度オゾンの発生要因としては都心部からの広域海風による輸送が主な要因であると考えられるが、過去の研究から海風の到達以前の高濃度オゾンの発生も報告されており、2009年夏季の観測データからも同様の現象が確認された。この問題を理解するため、混合層の発達による上空のオゾンの取り込みのみを考慮したボックスモデルを用いて解析を行った。その結果、正午における濃度はかなりの過小評価となり、濃度の増加傾向も観測値と異なるものであった。この原因としては化学反応によるオゾンの生成、消滅の影響が考えられる。また、赤城山におけるドップラーライダ観測とオゾン濃度の測定から、夜間山頂付近のオゾン濃度がほぼ一定でかつ風速が大きいという現象が観測された。これらより関東地方北部の上空が濃度のほぼ等しいオゾンによって覆われており、その気塊が常に内陸へ輸送され続けることでオゾン濃度がほぼ変化しない状態が実現していると推察された。

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.

電力中央研究所では，ヨーロッパや北アメリカで提案された指針を参考に独自の観測ネットワークを構築し，1987年10月に全国規模の降水成分のモニタリングを開始した。全国規模のモニタリングは1996年9月に終了したが，東京都狛江市ではその後も測定方法をほとんど変えることなく，20年以上にわたってモニタリングを続けてきた。本論文ではこの観測データを用いて，非海塩起源の陰イオンの濃度の経年変化や季節変化や降水量との関係を調べ，東京都内における降水の質的変化の実態を明らかにするとともに，前駆物質の排出量の抑制効果との関係について考察を加えた。&lt;BR&gt;狛江における非海塩起源の硫酸イオンに対する硝酸イオンの当量濃度比は，1980年代から1990年代にかけて増加したが，2000年の三宅島の噴火に伴って急減し，2003年ころからおむね一定の値で推移してきた。非海塩起源の陰イオンの総量に占める硝酸，硫酸，塩化物の各イオンの割合は，1980年代のおわりには31：53：16であり，全量の半分以上を硫酸イオンが占めた。1990年代のおわりになると，各イオンの割合は48：44：8となり，硫酸イオンと硝酸イオンの順位が逆転するとともに，塩化物イオンの占める割合は半減した。2000年代のおわりになると，各イオンの割合は40：56：4となり，硝酸イオンと硫酸イオンの順位が再逆転するとともに，塩化物イオンの占める割合はさらに半減した。2000年の三宅島の噴火にともなって，降水中の硫酸イオンと塩化物イオンの濃度は特異的に上昇した。降水量が平年値より大きく増減した期間の成分濃度は，その影響を受けて減増した。塩化物イオンの濃度の経年的な減少には，1999年のダイオキシン類特別措置法の施行のまえから，首都圏の廃棄物焼却炉における塩化水素の排出量の抑制効果が，少しずつ現れていたのではないかと推定された。

レセプターモデルを用いて炭素成分に注目して微小粒子状物質の発生源推定を行った。観測は2007年夏季に前橋と騎西で行い，6時間（日中）または12時間（夜間）ごとにPM&lt;SUB&gt;2.5&lt;/SUB&gt;を捕集し，炭素成分，イオン成分，無機元素成分および放射性炭素同位体比を分析した。このデータにCMB（Chemical Mass Balance）法を適用し，10種の発生源による寄与割合の推定を行った。この結果から炭素成分を発生源別に割り振ったところ，元素状炭素（Elemental Carbon; EC）はほとんどがディーゼル自動車排ガス由来であったが，有機炭素（Organic Carbon; OC）は一次粒子の寄与が少なく，ほとんどが二次生成によるものと推定された。発生源別に文献値等から設定したpMC（Percent Modern Carbon）の値からEC，OCを化石燃料起源と生物起源にわけると，ECはおおむね化石燃料起源であり，EC濃度の変動は日中に高く夜間に低かった。一方，二次生成の有機炭素（Secondary Organic Carbon; SOC）は日中には化石燃料起源と生物起源がほぼ1:2で存在するが，夜間には都心部からの移流に由来する化石燃料起源の割合が低下していた。その結果，観測された全炭素のpMCが増大することがわかった。また，日中にはSOCの70％が生物起源であり，SOCの前駆体として生物起源炭素が主要な寄与を持つことが示唆された。

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.

O&lt;SUB&gt;3&lt;/SUB&gt;とPM&lt;SUB&gt;2.5&lt;/SUB&gt;の予測性能を評価するために、関東地方において化学輸送モデル(CTM)の相互比較を行い、2007年夏季の観測データと比較した。参加した４グループ全てがCTMとしてCMAQを利用しており、排出インベントリは各々が異なるデータを利用していた。全てのCTMがO&lt;SUB&gt;3&lt;/SUB&gt;濃度とその経時変動を比較的良く再現していたが(r&gt;0.5)、PM&lt;SUB&gt;2.5&lt;/SUB&gt;を過小評価し、郊外においてはその経時変動の再現性も低かった(r&lt;0.5)。PM&lt;SUB&gt;2.5&lt;/SUB&gt;成分について、CTMはSO&lt;SUB&gt;4&lt;/SUB&gt;&lt;SUP&gt;2-&lt;/SUP&gt;を濃度・経時変動ともに比較的良く再現していたが(r&gt;0.5)、元素状炭素エアロゾル(EC)、有機エアロゾル(OA)を過小評価していた。また、CTM間でNO&lt;SUB&gt;3&lt;/SUB&gt;&lt;SUP&gt;-&lt;/SUP&gt;濃度に10倍程度のばらつきが見られた。OAはPM&lt;SUB&gt;2.5&lt;/SUB&gt;濃度の31%-41%を占めており、その過小評価がPM&lt;SUB&gt;2.5&lt;/SUB&gt;濃度の過小評価の大きな原因であった。今後、PM&lt;SUB&gt;2.5&lt;/SUB&gt;の再現性向上のためには、OA再現性の向上が不可欠である。また、NO&lt;SUB&gt;x&lt;/SUB&gt;やECなどの一次排出成分濃度のCTM間のばらつきは、排出量の差異によって概ね説明されたが、二次生成成分である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;)、二次有機エアロゾル濃度のCTM間のばらつきは境界濃度や前駆物質の差異によって説明されなかった。これらの成分の化学生成速度は前駆物質濃度に非線形に応答する事を反映しており、今後詳細な濃度制御要因解明が必要である。

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.

首都圏を対象に, 原因物質の排出量抑制にともなう二次生成無機粒子 (SIA) の濃度の変化を, 数値シミュレーションにより調べた。シミュレーション計算に先立ち, 使用する数値モデルが観測されたSIA成分の濃度を精度よく再現することを確認した。計算の結果, SIAの長期平均濃度と短期高濃度は排出量抑制にともなって減少し, 排出量抑制がある程度有効なことがわかった。濃度の減少は夏季に顕著であったが, 冬季の濃度はむしろ増大する場合がみられた。こうしたSIA濃度の変化は, おもにNO&lt;SUB&gt;3&lt;/SUB&gt;&lt;SUP&gt;-&lt;/SUP&gt;濃度の変動によりもたらされていた。

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.

静岡県と山梨県の県境に位置する富士山 (標高3776m) を観測塔に見立て, 高度の異なる20地点で2005年7月12日から7月20日までの9日間, パッシブサンプラーを用いてオゾン濃度の鉛直分布を測定した。山麓の都市部3地点 (標高30m～460m) と丹沢山頂 (標高1540m) での自動計測器による測定データをもとに, オゾン濃度の時間変化についても解析を加えた。パッシブサンプラーによって観測期間に測定されたオゾンの平均濃度は, 混合層内で約20ppbv, 混合層より上層で約40ppbvであり, 高度1500m付近を境にして大きな変化がみられた。濃度分布のパターンは, 過去に報告された観測結果などと矛盾するものではなかった。&lt;BR&gt;自動計測器の観測結果から, 富士山頂から水平距離が20km以内の山麓の都市部ではオゾン濃度の日変化は大きく, 地域規模の大気汚染の影響を受けていることがわかった。一方, 富士山頂から東に約30km離れた丹沢山頂では, 夜間に富士山麓の都市部と同レベルまでオゾン濃度が低下することがあり, 高度1500m付近でも気象条件によっては, 地域規模の大気汚染の影響を受ける場合があることがわかった。このためほぼ同じ高度である富士山の中腹で観測されたオゾン濃度の大きな変化は, 地域規模の大気汚染の影響によるものと推定された。

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.

電力中央研究所で開発した大気中複数成分の同時測定が可能な開光路型分光計の測定可能波長領域には, 健康への影響が懸念されている浮遊粒子状物質 (SPM) の生成と深く係わりのある揮発性有機化合物 (VOC) の吸収帯が存在している。本研究では, 開光路型分光計を用いてVOC7成分とオゾン, 二酸化硫黄の同時濃度測定を試みた。測定スペクトルから気体濃度を推定する際には, 測定スペクトルに大きく影響している酸素分子の吸収構造を除去し, 濃度推定精度の向上を図っている。濃度推定値は, 同時に行った吸引大気の測定値との比較によって, 妥当性が検証された。比較の結果, 測定期間中に検出限界以下の濃度であった1成分を除く8成分について, 両者は良い相関を示した。また, VOCの濃度推定値の時間変化と, 化学発光法による窒素酸化物濃度の時間変化は良い一致を示し, VOCの発生源である自動車排ガスの影響を適正に捕らえていた。

1999年度に, SPMの全国平均の年平均濃度が急減し, 環境基準達成率が大きく改善された。この低濃度の実態を明らかにし, 気象要因を解析した。1999年度のSPMの全国平均濃度は, 月別には4月, 6～8月, 2月に低かった。このうち7, 8月の濃度低下は関東で著しく, 週単位で低濃度が連続したことが特徴的であった。そこで1999年7, 8月の関東について気象解析を行ったところ, 月間値では他年に比べて強風, 多雨であり, 全月的な濃度低下との関連が示唆された。しかし, 低濃度が連続した期間では低濃度と降水, 風速との関連性は乏しく, むしろ, ほぼ同一風向の風が維持され, 太平洋からの清浄な空気が流入し続けたことが要因であると考えられた。

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).

わが国の都市域 (東京都狛江市) において, 半揮発性成分 (硝酸塩, 塩化物, アンモニウム塩) をガス態, 微小粒子態, 粗大粒子態に分別し, それぞれの24時間濃度を1998年9月から3力年間ほぼ連続して測定した。 分別捕集には, デニューダ・フィルタパック法を採用した。&lt;BR&gt;観測により, 硝酸塩の全 (ガス態+微小粒子態+粗大粒子態) 濃度は季節的な変化に乏しいが, 各態への分配割合は, 夏季はガス態に冬季は微小粒子態に多い顕著な季節変動を示すことがわかった。 塩化物の全濃度は冬季に増加したが, これには微小粒子態の非海塩起源塩化物が寄与していた。 また, アンモニウム塩は濃度, 分配割合ともに顕著な季節変化を示さなかった。&lt;BR&gt;これらの観測結果を, ガス・微小粒子間の分配関係について解析したところ, 多成分系の平衡反応を考慮して計算したガス成分の濃度積は, やや過大ながらも, 観測値にほぼ整合することがわかった。 このことから, 微小粒子態成分は内部混合状態にあり, 対応するガス成分と平衡関係にあったことが示唆された。 ただし冬季については, 当該成分しか存在しない単成分系を仮定して求められた濃度積でも観測値を良好に近似したことから, 外部混合の仮定を適用可能と考えた。

大気の吸収スペクトルから大気中微量成分濃度を推定する手法として提案した多重微分スペクトル法を, 実測された吸収スペクトルに適用して, その実用性についての検証を行った。検証に先立って, 吸収スペクトルを測定するための開光路型分光計の開発を行った。開発した装置は, 人工光源と反射鏡により大気中に開光路を確保し, 分散型分光計により光路上の大気吸収スペクトルを測定するものである。この装置の検出器には, 提案した推定法のノイズ成分の増長を考慮して, 高SN比が期待できる, 二次元CCアレーセンサを採用した。開発した装置により取得された吸収スペクトルから, 二酸化窒素, オゾン, 二酸化硫黄, ホルムアルデヒドの大気中濃度の同時推定を行い, その結果を, 他の装置の測定値と比較した。両者の結果は良い一致を見せ, 多重微分スペクトルを用いた推定法の実用性を実証した。

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.

エネルギー消費と大気汚染物質排出制御に関する幾つかのシナリオのもとで,わが国の将来の酸性沈着量を予測した。現時点で現実的と思われる現計画規制シナリオと経済改革シナリオでは,2030年のわが国の硫黄沈着量は現在の10～20%増,窒素沈着は30%増となる。悲観的シナリオでは,日本海に面する地域の沈着量は2倍になる。酸性沈着量の増加は,主に朝鮮半島西側に位置する渤海,黄海周辺で大気汚染物質の排出量が増加することによって生じる。

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.

多様な発生源を考慮した全国の1994年度NH&lt;SUB&gt;3&lt;/SUB&gt;排出量および時空間分布の推定を行った。NH&lt;SUB&gt;3&lt;/SUB&gt;の総排出量は約0.52Mt/yと推定され, 排出部門では, 農業起源 (家畜排泄物および施肥) が0.34Mt/yと最も大きな寄与を占めるが, 都市活動起源のNH&lt;SUB&gt;3&lt;/SUB&gt;も0.15Mt/yと無視しえない量であることが推定された。同時に推定したNO&lt;SUB&gt;x&lt;/SUB&gt;とSO&lt;SUB&gt;x&lt;/SUB&gt;の排出データベースと比較すると, NH&lt;SUB&gt;3&lt;/SUB&gt;の排出はモル比でNO&lt;SUB&gt;x&lt;/SUB&gt;に対し0.8, SO&lt;SUB&gt;x&lt;/SUB&gt;に対し2.3に相当することが推定された。既往の大気中濃度測定による総アンモニア/総窒素酸化物比と排出量におけるNH&lt;SUB&gt;3&lt;/SUB&gt;/NO&lt;SUB&gt;x&lt;/SUB&gt;比の比較により, NH&lt;SUB&gt;3&lt;/SUB&gt;排出量の時空間分布の推計値に矛盾がないことが推定された。

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.