@article{kong_tang_zhu_wang_fu_wang_itahashi_yamaji_nagashima_lee_et al._2020, title={Evaluation and uncertainty investigation of the NO2, CO and NH3 modeling over China under the framework of MICS-Asia III}, volume={20}, ISSN={["1680-7324"]}, DOI={10.5194/acp-20-181-2020}, abstractNote={Abstract. Despite the significant progress in improving
chemical transport models (CTMs), applications of these modeling endeavors
are still subject to large and complex model uncertainty. The Model
Inter-Comparison Study for Asia III (MICS-Asia III) has provided the
opportunity to assess the capability and uncertainty of current CTMs in East
Asian applications. In this study, we have evaluated the multi-model
simulations of nitrogen dioxide (NO2), carbon monoxide (CO) and ammonia
(NH3) over China under the framework of MICS-Asia III. A total of 13
modeling results, provided by several independent groups from different
countries and regions, were used in this study. Most of these models used the same
modeling domain with a horizontal resolution of 45 km and were driven by
common emission inventories and meteorological inputs. New observations over the
North China Plain (NCP) and Pearl River Delta (PRD) regions were also
available in MICS-Asia III, allowing the model evaluations over highly
industrialized regions. The evaluation results show that most models
captured the monthly and spatial patterns of NO2 concentrations in the
NCP region well, though NO2 levels were slightly underestimated. Relatively
poor performance in NO2 simulations was found in the PRD region, with
larger root-mean-square error and lower spatial correlation coefficients,
which may be related to the coarse resolution or inappropriate spatial
allocations of the emission inventories in the PRD region. All models
significantly underpredicted CO concentrations in both the NCP and PRD
regions, with annual mean concentrations that were 65.4 % and 61.4 %
underestimated by the ensemble mean. Such large underestimations suggest
that CO emissions might be underestimated in the current emission inventory. In
contrast to the good skills for simulating the monthly variations in NO2
and CO concentrations, all models failed to reproduce the observed monthly
variations in NH3 concentrations in the NCP region. Most models
mismatched the observed peak in July and showed negative correlation
coefficients with the observations, which may be closely related to the
uncertainty in the monthly variations in NH3 emissions and the NH3
gas–aerosol partitioning. Finally, model intercomparisons have been
conducted to quantify the impacts of model uncertainty on the simulations of
these gases, which are shown to increase with the reactivity of species. Models
contained more uncertainty in the NH3 simulations. This suggests that
for some highly active and/or short-lived primary pollutants, like NH3,
model uncertainty can also take a great part in the forecast uncertainty
in addition to the emission uncertainty. Based on these results, some
recommendations are made for future studies.
                    }, number={1}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Kong, Lei and Tang, Xiao and Zhu, Jiang and Wang, Zifa and Fu, Joshua S. and Wang, Xuemei and Itahashi, Syuichi and Yamaji, Kazuyo and Nagashima, Tatsuya and Lee, Hyo-Jung and et al.}, year={2020}, month={Jan}, pages={181–202} }
 @article{itahashi_mathur_hogrefe_zhang_2020, title={Modeling stratospheric intrusion and trans-Pacific transport on tropospheric ozone using hemispheric CMAQ during April 2010-Part 1: Model evaluation and air mass characterization for stratosphere-troposphere transport}, volume={20}, ISSN={["1680-7324"]}, DOI={10.5194/acp-20-3373-2020}, abstractNote={Abstract. Stratospheric intrusion and trans-Pacific transport have been recognized as a
potential source of tropospheric ozone over the US. The
state-of-the-science Community Multiscale Air Quality (CMAQ) modeling system
has recently been extended for hemispheric-scale modeling applications
(referred to as H-CMAQ). In this study, H-CMAQ is applied to study the
stratospheric intrusion and trans-Pacific transport during April 2010. The
results will be presented in two companion papers. In this Part 1 paper,
model evaluation for tropospheric ozone (O3) is presented. Observations
at the surface, by ozonesondes and airplane, and by satellite across the
Northern Hemisphere are used to evaluate the model performance for O3.
H-CMAQ is able to capture surface and boundary layer (defined as surface to
750 hPa) O3 with a normalized mean bias (NMB) of −10 %; however, a
systematic underestimation with an NMB up to −30 % is found in the free
troposphere (defined as 750–250 hPa). In addition, a new air mass
characterization method is developed to distinguish influences of
stratosphere–troposphere transport (STT) from the effects of photochemistry
on O3 levels. This method is developed based on the ratio of O3
and an inert tracer indicating stratospheric O3 to examine the
importance of photochemistry, and sequential intrusion from upper layer.
During April 2010, on a monthly average basis, the relationship between
surface O3 mixing ratios and estimated stratospheric air masses in the
troposphere show a slight negative slope, indicating that high surface
O3 values are primarily affected by other factors (i.e., emissions),
whereas this relationship shows a slight positive slope at elevated sites,
indicating that STT has a possible impact at elevated sites. STT shows large
day-to-day variations, and STT impacts can either originate from the same
air mass over the entire US with an eastward movement found during early
April, or stem from different air masses at different locations indicated
during late April. Based on this newly established air mass characterization
technique, this study can contribute to understanding the role of STT and
also the implied importance of emissions leading to high surface O3.
Further research focused on emissions is discussed in a subsequent paper (Part 2).
                    }, number={6}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Itahashi, Syuichi and Mathur, Rohit and Hogrefe, Christian and Zhang, Yang}, year={2020}, month={Mar}, pages={3373–3396} }
 @article{itahashi_mathur_hogrefe_napelenok_zhang_2020, title={Modeling stratospheric intrusion and trans-Pacific transport on tropospheric ozone using hemispheric CMAQ during April 2010-Part 2: Examination of emission impacts based on the higher-order decoupled direct method}, volume={20}, ISSN={["1680-7324"]}, DOI={10.5194/acp-20-3397-2020}, abstractNote={Abstract. The state-of-the-science Community Multiscale Air Quality (CMAQ) modeling
system, which has recently been extended for hemispheric-scale modeling
applications (referred to as H-CMAQ), is applied to study the trans-Pacific
transport, a phenomenon recognized as a potential source of air pollution in
the US, during April 2010. The results of this analysis are presented in
two parts. In the previous paper (Part 1), model evaluation for tropospheric
ozone (O3) was presented and an air mass characterization method was
developed. Results from applying this newly established method pointed to
the importance of emissions as the factor to enhance the surface O3 mixing
ratio over the US. In this subsequent paper (Part 2), emission impacts are
examined based on mathematically rigorous sensitivity analysis using the
higher-order decoupled direct method (HDDM) implemented in H-CMAQ. The HDDM
sensitivity coefficients indicate the presence of a NOx-sensitive
regime during April 2010 over most of the Northern Hemisphere. By defining
emission source regions over the US and east Asia, impacts from these
emission sources are examined. At the surface, during April 2010, the
emission impacts of the US and east Asia are comparable over the western
US with a magnitude of about 3 ppbv impacts on monthly mean O3
all-hour basis, whereas the impact of domestic emissions dominates over the
eastern US with a magnitude of about 10 ppbv impacts on monthly mean
O3. The positive correlation (r=0.63) between surface O3 mixing
ratios and domestic emission impacts is confirmed. In contrast, the
relationship between surface O3 mixing ratios and emission impacts from
east Asia exhibits a flat slope when considering the entire US. However,
this relationship has strong regional differences between the western and
eastern US; the western region exhibits a positive correlation
(r=0.36–0.38), whereas the latter exhibits a flat slope (r < 0.1).
Based on the comprehensive evaluation of H-CMAQ, we extend the sensitivity
analysis for O3 aloft. The results reveal the significant impacts of
emissions from east Asia on the free troposphere (defined as 750 to 250 hPa)
over the US (impacts of more than 5 ppbv) and the dominance of
stratospheric air mass on upper model layer (defined as 250 to 50 hPa) over
the US (impacts greater than 10 ppbv). Finally, we estimate changes of
trans-Pacific transport by taking into account recent emission trends from
2010 to 2015 assuming the same meteorological condition. The analysis
suggests that the impact of recent emission changes on changes in the
contribution of trans-Pacific transport to US O3 levels was
insignificant at the surface level and was small (less than 1 ppbv) over the free troposphere.
                    }, number={6}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Itahashi, Syuichi and Mathur, Rohit and Hogrefe, Christian and Napelenok, Sergey L. and Zhang, Yang}, year={2020}, month={Mar}, pages={3397–3413} }
 @article{chen_gao_zhang_fu_zhu_liao_li_huang_ge_wang_et al._2019, title={MICS-Asia III: multi-model comparison and evaluation of aerosol over East Asia}, volume={19}, ISSN={["1680-7324"]}, DOI={10.5194/acp-19-11911-2019}, abstractNote={Abstract. A total of 14 chemical transport models (CTMs) participated in
the first topic of the Model Inter-Comparison Study for Asia (MICS-Asia)
phase III. These model results are compared with each other and an extensive
set of measurements, aiming to evaluate the current CTMs' ability in
simulating aerosol concentrations, to document the similarities and
differences among model performance, and to reveal the characteristics of
aerosol components in large cities over East Asia. In general, these CTMs
can well reproduce the spatial–temporal distributions of aerosols in East
Asia during the year 2010. The multi-model ensemble mean (MMEM) shows
better performance than most single-model predictions, with correlation
coefficients (between MMEM and measurements) ranging from 0.65 (nitrate,
NO3-) to 0.83 (PM2.5). The
concentrations of black carbon (BC), sulfate
(SO42-), and PM10 are
underestimated by MMEM, with normalized mean biases (NMBs) of −17.0 %,
−19.1 %, and −32.6 %, respectively. Positive biases are simulated
for NO3- (NMB = 4.9 %), ammonium
(NH4+) (NMB = 14.0 %), and PM2.5
(NMB = 4.4 %). In comparison with the statistics calculated from
MICS-Asia phase II, frequent updates of chemical mechanisms in CTMs during
recent years make the intermodel variability of simulated aerosol
concentrations smaller, and better performance can be found in reproducing
the temporal variations of observations. However, a large variation (about a
factor of 2) in the ratios of SNA (sulfate, nitrate, and ammonium) to
PM2.5 is calculated among participant models. A more intense secondary
formation of SO42- is simulated by Community Multi-scale Air Quality (CMAQ)
models, because of the higher SOR (sulfur oxidation ratio) than other
models (0.51 versus 0.39). The NOR (nitric oxidation ratio) calculated by all
CTMs has larger values (∼0.20) than the observations,
indicating that overmuch NO3- is
simulated by current models. NH3-limited condition (the mole ratio of
ammonium to sulfate and nitrate is smaller than 1) can be successfully
reproduced by all participant models, which indicates that a small reduction
in ammonia may improve the air quality. A large coefficient of variation
(CV > 1.0) is calculated for simulated coarse particles,
especially over arid and semi-arid regions, which means that current CTMs
have difficulty producing similar dust emissions by using different dust
schemes. According to the simulation results of MMEM in six large Asian
cities, different air-pollution control plans should be taken due to
their different major air pollutants in different seasons. The MICS-Asia
project gives an opportunity to discuss the similarities and differences of
simulation results among CTMs in East Asian applications. In order to acquire
a better understanding of aerosol properties and their impacts, more
experiments should be designed to reduce the diversities among air quality
models.
                    }, number={18}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Chen, Lei and Gao, Yi and Zhang, Meigen and Fu, Joshua S. and Zhu, Jia and Liao, Hong and Li, Jialin and Huang, Kan and Ge, Baozhu and Wang, Xuemei and et al.}, year={2019}, month={Sep}, pages={11911–11937} }
 @article{itahashi_hatakeyama_shimada_takami_2019, title={Sources of High Sulfate Aerosol Concentration Observed at Cape Hedo in Spring 2012}, volume={19}, ISSN={["2071-1409"]}, DOI={10.4209/aaqr.2018.09.0350}, abstractNote={ABSTRACT

Intensive observation campaigns approximately 1 week long were conducted periodically from March 2010 to November 2015 at Cape Hedo, Okinawa, Japan. The maximum daily mean sulfate aerosol (SO42–) concentrations surpassed 15 µg m–3 in spring 2012. In this study, source apportionment for these high concentrations was conducted using an air quality model with the tagged tracer method, and the main source was identified as volcanoes in March and as anthropogenic emissions from China in April. In March, the prevailing northerly wind transported a volcanic SO2 plume with a low conversion ratio to Cape Hedo. The impacts of 15 volcanoes in Japan were estimated, and a substantial impact from Sakurajima, which accounted for more SO2 than anthropogenic emissions from Japan, was found. Because the model had difficulty capturing the highest concentration, three sensitivity simulations were performed to consider the uncertainty of the volcanic SO2 emission amounts and injection heights, revealing the importance of the injection height in addition to the SO2 emission amount. Throughout April, contributions from anthropogenic emissions from China were found; hence, this source was further divided into 31 provincial scales. Shandong and Jiangsu Provinces, which are the first and seventh largest emission sources in China, respectively, were identified as significant sources at Cape Hedo. These sources showed day-to-day variation in their contributions, and the highest contribution from Shandong Province occurred on April 23, whereas that from Jiangsu Province occurred on April 22.}, number={3}, journal={AEROSOL AND AIR QUALITY RESEARCH}, author={Itahashi, Syuichi and Hatakeyama, Shiro and Shimada, Kojiro and Takami, Akinori}, year={2019}, month={Mar}, pages={587–600} }
 @article{itahashi_yamaji_chatani_hisatsune_saito_hayami_2018, title={Model Performance Differences in Sulfate Aerosol in Winter over Japan Based on Regional Chemical Transport Models of CMAQ and CAMx}, volume={9}, ISSN={["2073-4433"]}, DOI={10.3390/atmos9120488}, abstractNote={Sulfate aerosol (SO42−) is a major component of particulate matter in Japan. The Japanese model intercomparison study, J-STREAM, found that although SO42− 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 SO42− concentrations than CAMx, despite increased aqueous oxidation via the metal catalysis pathway and NO2 reaction in CMAQ. Deposition explained this difference. A scatter plot demonstrated that the lower SO42− concentration in CMAQ than in CAMx arose from the lower SO2 concentration and higher SO42− wet deposition in CMAQ. The dry deposition velocity caused the difference in SO2 concentration. These results suggest the importance of deposition in improving our understanding of ambient concentration behavior.}, number={12}, journal={ATMOSPHERE}, author={Itahashi, Syuichi and Yamaji, Kazuyo and Chatani, Satoru and Hisatsune, Kunihiro and Saito, Shinji and Hayami, Hiroshi}, year={2018}, month={Dec} }
 @article{chatani_yamaji_sakurai_itahashi_shimadera_kitayama_hayami_2018, title={Overview of Model Inter-Comparison in Japan's Study for Reference Air Quality Modeling (J-STREAM)}, volume={9}, ISSN={["2073-4433"]}, DOI={10.3390/atmos9010019}, abstractNote={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.}, number={1}, journal={ATMOSPHERE}, author={Chatani, Satoru and Yamaji, Kazuyo and Sakurai, Tatsuya and Itahashi, Syuichi and Shimadera, Hikari and Kitayama, Kyo and Hayami, Hiroshi}, year={2018}, month={Jan} }
 @article{itahashi_yamaji_chatani_hayami_2018, title={Refinement of Modeled Aqueous-Phase Sulfate Production via the Fe- and Mn-Catalyzed Oxidation Pathway}, volume={9}, ISSN={["2073-4433"]}, DOI={10.3390/atmos9040132}, abstractNote={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.}, number={4}, journal={ATMOSPHERE}, author={Itahashi, Syuichi and Yamaji, Kazuyo and Chatani, Satoru and Hayami, Hiroshi}, year={2018}, month={Apr} }
 @article{itahashi_2018, title={Toward Synchronous Evaluation of Source Apportionments for Atmospheric Concentration and Deposition of Sulfate Aerosol Over East Asia}, volume={123}, ISSN={["2169-8996"]}, DOI={10.1002/2017jd028110}, abstractNote={Abstract}, number={5}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Itahashi, S.}, year={2018}, month={Mar}, pages={2927–2953} }