Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Keiya Yumimoto Last modified date:2020.01.08

Associate Professor / Division of Earth Environment Dynamics / Research Institute for Applied Mechanics

1. Mizuo Kajino, Makoto Deushi, Tsuyoshi Thomas Sekiyama, Naga Oshima, Keiya Yumimoto, Taichu Yasumichi Tanaka, Joseph Ching, Akihiro Hashimoto, Tetsuya Yamamoto, Masaaki Ikegami, Akane Kamada, Makoto Miyashita, Yayoi Inomata, Shin Ichiro Shima, Akinori Takami, Atsushi Shimizu, Shiro Hatakeyama, NHM-Chem, the Japan meteorological agency’s regional meteorology – chemistry model
Model evaluations toward the consistent predictions of the chemical, physical, and optical properties of aerosols, Journal of the Meteorological Society of Japan, 10.2151/JMSJ.2019-020, 97, 2, 337-374, 2019.01, The model performance of a regional-scale meteorology-chemistry model (NHM-Chem) has been evaluated for the consistent predictions of the chemical, physical, and optical properties of aerosols. These properties are essentially important for the accurate assessment of air quality and health hazards, contamination of land and ocean ecosystems, and regional climate changes due to aerosol-cloud-radiation interaction processes. Currently, three optional methods are available: the five-category non-equilibrium method, the three-category non-equilibrium method, and the bulk equilibrium method. These three methods are suitable for the predictions of regional climate, air quality, and operational forecasts, respectively. In this paper, the simulated aerosol chemical, physical, and optical properties and their consistency were evaluated using various observation data in East Asia. The simulated mass, size, and deposition of SO42− and NH4 + agreed well with the observations, whereas those of NO3−, sea salt, and dust needed improvement. The simulated surface mass concentration (PM10 and PM2.5) and spherical extinction coefficient agreed well with the observations. The simulated aerosol optical thickness (AOT) and dust extinction coefficient were significantly underestimated..
2. Keiya Yumimoto, Mizuo Kajino, Taichu Y. Tanaka, Itsushi Uno, Dust Vortex in the Taklimakan Desert by Himawari-8 High Frequency and Resolution Observation, Scientific reports, 10.1038/s41598-018-37861-4, 9, 1, 2019.12, The Taklimakan Desert is known to be one of the world’s major sources of aeolian dust particles. Continuous images with 10-min temporal and 2-km spatial resolutions from a new-generation geostationary meteorological satellite captured the lifecycle (generation, evolution and outflow) of a previously unrecognized type of Taklimakan dust storm. The dust storm showed an anti-clockwise spiral structure and a clear core and behaved like a “dust vortex”. From image analysis, the horizontal scale and temporal lifetime of the dust vortex were estimated to be 600 km and 36 hours, respectively. We found that a strong pressure trough (cut-off low), along with a cold air mass located on the northwestern side of the Taklimakan Desert and the high mountains surrounding the Taklimakan Desert, played important roles in the formation and evolution of the dust vortex..
3. Peng Xian, Jeffrey S. Reid, Edward J. Hyer, Charles R. Sampson, Juli I. Rubin, Melanie Ades, Nicole Asencio, Sara Basart, Angela Benedetti, Partha S. Bhattacharjee, Malcolm E. Brooks, Peter R. Colarco, Arlindo M. da Silva, Tom F. Eck, Jonathan Guth, Oriol Jorba, Rostislav Kouznetsov, Zak Kipling, Mikhail Sofiev, Carlos Perez Garcia-Pando, Yaswant Pradhan, Taichu Tanaka, Jun Wang, Douglas L. Westphal, Keiya Yumimoto, Jianglong Zhang, Current state of the global operational aerosol multi-model ensemble
An update from the International Cooperative for Aerosol Prediction (ICAP), Quarterly Journal of the Royal Meteorological Society, 10.1002/qj.3497, 2019.01, Since the first International Cooperative for Aerosol Prediction (ICAP) multi-model ensemble (MME) study, the number of ICAP global operational aerosol models has increased from five to nine. An update of the current ICAP status is provided, along with an evaluation of the performance of ICAP-MME over 2012–2017, with a focus on June 2016–May 2017. Evaluated with ground-based Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) and data assimilation quality MODerate-resolution Imaging Spectroradiometer (MODIS) retrieval products, the ICAP-MME AOD consensus remains the overall top-scoring and most consistent performer among all models in terms of root-mean-square error (RMSE), bias and correlation for total, fine- and coarse-mode AODs as well as dust AOD; this is similar to the first ICAP-MME study. Further, over the years, the performance of ICAP-MME is relatively stable and reliable compared to more variability in the individual models. The extent to which the AOD forecast error of ICAP-MME can be predicted is also examined. Leading predictors are found to be the consensus mean and spread. Regression models of absolute forecast errors were built for AOD forecasts of different lengths for potential applications. ICAP-MME performance in terms of modal AOD RMSEs of the 21 regionally representative sites over 2012–2017 suggests a general tendency for model improvements in fine-mode AOD, especially over Asia. No significant improvement in coarse-mode AOD is found overall for this time period..
4. Yukari Hara, Tomoaki Nishizawa, Nobuo Sugimoto, Kazuo Osada, Keiya Yumimoto, Itsushi Uno, Rei Kudo, Hiroshi Ishimoto, Retrieval of aerosol components using multi-wavelength Mie-Raman lidar and comparison with ground aerosol sampling, Remote Sensing, 10.3390/rs10060937, 10, 6, 2018.06, We verified an algorithm using multi-wavelength Mie-Raman lidar (MMRL) observations to retrieve four aerosol components (black carbon (BC), sea salt (SS), air pollution (AP), and mineral dust (DS)) with in-situ aerosol measurements, and determined the seasonal variation of aerosol components in Fukuoka, in the western region of Japan. PM
, PM
, and mass concentrations of BC and SS components are derived from in-situ measurements. MMRL provides the aerosol extinction coefficient (α), particle linear depolarization ratio (δ), backscatter coefficient (β), and lidar ratio (S) at 355 and 532 nm, and the attenuated backscatter coefficient (β
) at 1064 nm. We retrieved vertical distributions of extinction coefficients at 532 nm for four aerosol components (BC, SS, AP, and DS) using 1α
+ 1β
+ 1β
+ 1δ
data of MMRL. The retrieved extinction coefficients of the four aerosol components at 532 nm were converted to mass concentrations using the theoretical computed conversion factor assuming the prescribed size distribution, particle shape, and refractive index for each aerosol component. MMRL and in-situ measurements confirmed that seasonal variation of aerosol optical properties was affected by internal/external mixing of various aerosol components, in addition to hygroscopic growth of water-soluble aerosols. MMRL overestimates BC mass concentration compared to in-situ observation using the pure BC model. This overestimation was reduced drastically by introducing the internal mixture model of BC and water-soluble substances (Core-Gray Shell (CGS) model). This result suggests that considering the internal mixture of BC and water-soluble substances is essential for evaluating BC mass concentration in this area. Systematic overestimation of BC mass concentration was found during summer, even when we applied the CGS model. The observational facts based on in-situ and MMRL measurements suggested that misclassification of AP as CGS particles was due to underestimation of relative humidity (RH) by the numerical model in lidar analysis, as well as mismatching of the optical models of AP and CGS assumed in the retrieval with aerosol properties in the actual atmosphere. The time variation of lidar-derived SS was generally consistent with in-situ measurement; however, we found some overestimation of SS during dust events. The cause of this SS overestimation is mainly due to misclassifying internally mixing DS as SS, implying that to consider internal mixing between DS and water-soluble substances leads to better estimation. The time-variations of PM
and PM
generally showed good agreement with in-situ measurement although lidar-derived PM
and PM
overestimated in dust events..
5. Syuichi Itahashi, Keiya Yumimoto, Itsushi Uno, Hiroshi Hayami, Shin Ichi Fujita, Yuepeng Pan, Yuesi Wang, A 15-year record (2001-2015) of the ratio of nitrate to non-sea-salt sulfate in precipitation over East Asia, Atmospheric Chemistry and Physics, 10.5194/acp-18-2835-2018, 18, 4, 2835-2852, 2018.02, 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..
6. Keiya Yumimoto, Taichu Y. Tanaka, Mayumi Yoshida, Maki Kikuchi, Takashi M. Nagao, Hiroshi Murakami, Takashi Maki, Assimilation and forecasting experiment for heavy siberian wildfire smoke in may 2016 with himawari-8 aerosol optical thickness, Journal of the Meteorological Society of Japan, 10.2151/jmsj.2018-035, 96B, 2018.01, The Japan Meteorological Agency (JMA) launched a next-generation geostationary meteorological satellite (GMS), Himawari-8, on October 7, 2014, which began its operation on July 7, 2015. The Advanced Himawari Imager (AHI) onboard Himawari-8 has 16 observational bands that enable the retrieval of full-disk maps of aerosol optical properties (AOPs), including aerosol optical thickness (AOT) and the Ångström exponent (AE), with unprecedented spatial and temporal resolutions. In this study, we combined an aerosol transport model with the Himawari-8 AOT using the data assimilation method and performed aerosol assimilation and forecasting experiments on smoke from an intensive wildfire that occurred over Siberia between May 15 and 18, 2016. To effectively utilize the high observational frequency of Himawari-8, we assimilated 1-h merged AOTs generated through the combination of six AOT snapshots taken over 10-min intervals, three times per day. The heavy smoke originating from the wildfire was transported eastward behind a low-pressure trough and covered northern Japan from May 19 to 20. The southern part of the smoke plume then traveled westward, in a clockwise flow associated with high pressure. The forecast without assimilation reproduced the transport of the smoke to northern Japan; however, it underestimated AOT and the extinction coefficient compared with observed values mainly because of errors in the emission inventory. Data assimilation with the Himawari-8 AOT compensated for the un-derestimation and successfully forecasted the unique C-shaped distribution of the smoke. In particular, the assimilation of the Himawari-8 AOT in May 18 greatly improved the forecast of the southern part of the smoke flow. Our results indicate that the inheritance of assimilation cycles and the assimilation of more recent observations led to better forecasting in this case of a continental smoke outflow..
7. Mizuo Kajino, Tsuyoshi Thomas Sekiyama, Anne Mathieu, Irène Korsakissok, Raphaël Périllat, Denis Quélo, Arnaud Quérel, Olivier Saunier, Kouji Adachi, Sylvain Girard, Takashi Maki, Keiya Yumimoto, Damien Didier, Olivier Masson, Yasuhito Igarashi, Lessons learned from atmospheric modeling studies after the Fukushima nuclear accident
Ensemble simulations, data assimilation, elemental process modeling, and inverse modeling, GEOCHEMICAL JOURNAL, 10.2343/geochemj.2.0503, 52, 2, 85-101, 2018.01, Modeling studies on the atmospheric diffusion and deposition of the radiocesium associated with the Fukushima Daiichi Nuclear Power Plant accident is reviewed here, with a focus on a research collaboration between l’Institut de Radioprotection et de Sûreté Nucléaire (IRSN)—the French institute in charge of evaluating the consequences of nuclear accidents and advising authorities in case of a crisis—and the Meteorological Research Institute (MRI) of the Japan Meteorological Agency—an operational weather forecasting center in Japan. While the modelers have come to know that wet deposition is one of the key processes, the size of its influence is unknown. They also know that the simulation results vary, but they do not know exactly why. Under the research collaboration, we aimed to understand the atmospheric processes, especially wet deposition, and to quantify the uncertainties of each component of our simulation using various numerical techniques, such as ensemble simulations, data assimilation, elemental process modeling, and inverse modeling. The outcomes of these collaborative research topics are presented in this paper. We also discuss the future directions of atmospheric modeling studies: data assimilation using the high temporal and spatial resolution surface concentration measurement data, and consideration of aerosol properties such as size and hygroscopicity into wet and dry deposition schemes..
8. Itsushi Uno, Kazuo Osada, Keiya Yumimoto, Zhe Wang, Syuichi Itahashi, Xiaole Pan, Yukari Hara, Shigekazu Yamamoto, Tomoaki Nishizawa, Importance of long-range nitrate transport based on long-term observation and modeling of dust and pollutants over East Asia, Aerosol and Air Quality Research, 10.4209/aaqr.2016.11.0494, 17, 12, 3052-3064, 2017.12, Long-term synergetic fine and coarse mode aerosol observations were analyzed at 1-h intervals at Fukuoka, Japan, from January to June 2015. The GEOS-Chem chemical transport model, including dust and sea-salt acid uptake processes, was used for detailed analysis of observation data. Several Asian dust events and long-range anthropogenic aerosol transport events were observed during our analysis period, and the numerical model generally explained the observed time variation for both fine and coarse mode aerosols. We found that (i) the majority of fine mode NO3 can be considered as long-range transport (LRT) outside of Japan during the cold season, and (ii) the peak timing of fine mode NO3 coincided with that of SO4 , indicating that both aerosols are controlled by LRT. Also, an observed mass concentration ratio of NO3 /SO4 2– > 0.9 occurred during the cold season, indicating the importance of NO3 as a major contributor to the PM2.5 mass fraction. Finally, we clearly showed that large-scale dust-nitrate outflow from China to Fukuoka was confirmed in all cases of dust events, indicating that the anthropogenic NOx is converted to dust-nitrate and transported to Japan with dust. These results demonstrate the importance of anthropogenic NO3 LRT during the cold season and dust-nitrate LRT for all dust events (even in June)..
9. Itsushi Uno, Kazuo Osada, Keiya Yumimoto, Zhe Wang, Syuichi Itahashi, Xiaole Pan, Yukari Hara, Yugo Kanaya, Shigekazu Yamamoto, Thomas Duncan Fairlie, Seasonal variation of fine- and coarse-mode nitrates and related aerosols over East Asia
Synergetic observations and chemical transport model analysis, Atmospheric Chemistry and Physics, 10.5194/acp-17-14181-2017, 17, 23, 14181-14197, 2017.11, We analyzed long-term fine- and coarse-mode synergetic observations of nitrate and related aerosols (SO2 4 , NO3 , NHC4 , NaC, Ca2C) at Fukuoka (33.52 N, 130.47 E) from August 2014 to October 2015. A Goddard Earth Observing System chemical transport model (GEOS-Chem) including dust and sea salt acid uptake processes was used to assess the observed seasonal variation and the impact of long-range transport (LRT) from the Asian continent. For fine aerosols (fSO2 4 , fNO3 , and fNHC4 ), numerical results explained the seasonal changes, and a sensitivity analysis excluding Japanese domestic emissions clarified the LRT fraction at Fukuoka (85% for fSO2 4 , 47% for fNO3 , 73% for fNHC4 ). Observational data confirmed that coarse NO3 (cNO3 ) made up the largest proportion (i.e., 40-55 %) of the total nitrate (defined as the sum of fNO3 , cNO3 , and HNO3) during the winter, while HNO3 gas constituted approximately 40% of the total nitrate in summer and fNO3 peaked during the winter. Large-scale dust-nitrate (mainly cNO3 ) outflow from China to Fukuoka was confirmed during all dust events that occurred between January and June. The modeled cNO3 was in good agreement with observations between July and November (mainly coming from sea salt NO3 ). During the winter, however, the model underestimated cNO3 levels compared to the observed levels. The reason for this underestimation was examined statistically using multiple regression analysis (MRA).We used cNaC, nsscCa2 C, and cNHC4 as independent variables to describe the observed cNO3 levels; these variables were considered representative of sea salt cNO3 , dust cNO3 , and cNO3 accompanied by cNHC4 ), respectively. The MRA results explained the observed seasonal changes in dust cNO3 and indicated that the dust-acid uptake scheme reproduced the observed dust-nitrate levels even in winter. The annual average contributions of each component were 43% (sea salt cNO3 ), 19% (dust cNO3 ), and 38% (cNHC4 term). The MRA dust-cNO3 component had a high value during the dust season, and the sea salt component made a large contribution throughout the year. During the winter, cNHC4 term made a large contribution. The model did not include aerosol microphysical processes (such as condensation and coagulation between the fine anthropogenic aerosols NO3 and SO2 4 and coarse particles), and our results suggest that inclusion of aerosol microphysical processes is critical when studying observed cNO3 formation, especially in winter..
10. Keiya Yumimoto, Taichu Y. Tanaka, Naga Oshima, Takashi Maki, JRAero
The Japanese Reanalysis for Aerosol v1.0, Geoscientific Model Development, 10.5194/gmd-10-3225-2017, 10, 9, 3225-3253, 2017.09, A global aerosol reanalysis product named the Japanese Reanalysis for Aerosol (JRAero) was constructed by the Meteorological Research Institute (MRI) of the Japan Meteorological Agency. The reanalysis employs a global aerosol transport model developed by MRI and a twodimensional variational data assimilation method. It assimilates maps of aerosol optical depth (AOD) from MODIS onboard the Terra and Aqua satellites every 6 h and has a TL159 horizontal resolution (approximately 1.1° × 1.1°). This paper describes the aerosol transport model, the data assimilation system, the observation data, and the setup of the reanalysis and examines its quality with AOD observations. Comparisons with MODIS AODs that were used for the assimilation showed that the reanalysis showed much better agreement than the free run (without assimilation) of the aerosol model and improved under- and overestimation in the free run, thus confirming the accuracy of the data assimilation system. The reanalysis had a root mean square error (RMSE) of 0.05, a correlation coefficient (R) of 0.96, a mean fractional error (MFE) of 23.7 %, a mean fractional bias (MFB) of 2.8 %, and an index of agreement (IOA) of 0.98. The better agreement of the first guess, compared to the free run, indicates that aerosol fields obtained by the reanalysis can improve short-term forecasts. AOD fields from the reanalysis also agreed well with monthly averaged global AODs obtained by the Aerosol Robotic Network (AERONET) (RMSED0.08, R D 0:90, MFED28.1 %, MFBD0.6 %, and IOAD0.93). Site-by-site comparison showed that the reanalysis was considerably better than the free run; RMSE was less than 0.10 at 86.4% of the 181 AERONET sites, R was greater than 0.90 at 40.7% of the sites, and IOA was greater than 0.90 at 43.4% of the sites. However, the reanalysis tended to have a negative bias at urban sites (in particular, megacities in industrializing countries) and a positive bias at mountain sites, possibly because of insufficient anthropogenic emissions data, the coarse model resolution, and the difference in representativeness between satellite and ground-based observations..
11. Osamu Uchino, Tetsu Sakai, Toshiharu Izumi, Tomohiro Nagai, Isamu Morino, Akihiro Yamazaki, Makoto Deushi, Keiya Yumimoto, Takashi Maki, Taichu Y. Tanaka, Taiga Akaho, Hiroshi Okumura, Kohei Arai, Takahiro Nakatsuru, Tsuneo Matsunaga, Tatsuya Yokota, Lidar detection of high concentrations of ozone and aerosol transported from northeastern Asia over Saga, Japan, Atmospheric Chemistry and Physics, 10.5194/acp-17-1865-2017, 17, 3, 1865-1879, 2017.02, To validate products of the Greenhouse gases Observing SATellite (GOSAT), we observed vertical profiles of aerosols, thin cirrus clouds, and tropospheric ozone with a mobile-lidar system that consisted of a two-wavelength (532 and 1064 nm) polarization lidar and a tropospheric ozone differential absorption lidar (DIAL). We used these lidars to make continuous measurements over Saga (33.24° N, 130.29° E) during 20-31 March 2015. High ozone and high aerosol concentrations were observed almost simultaneously in the altitude range 0.5-1.5 km from 03:00 to 20:00 Japan Standard Time (JST) on 22 March 2015. The maximum ozone volume mixing ratio was ∼110 ppbv. The maxima of the aerosol extinction coefficient and optical depth at 532 nm were 1.2 km-1 and 2.1, respectively. Backward trajectory analysis and the simulations by the Model of Aerosol Species IN the Global AtmospheRe (MASINGAR) mk-2 and the Meteorological Research Institute Chemistry-Climate Model, version 2 (MRI-CCM2), indicated that mineral dust particles from the Gobi Desert and an air mass with high ozone and aerosol (mainly sulfate) concentrations that originated from the North China Plain could have been transported over the measurement site within about 2 days. These high ozone and aerosol concentrations impacted surface air quality substantially in the afternoon of 22 March 2015. After some modifications of its physical and chemical parameters, MRI-CCM2 approximately reproduced the high ozone volume mixing ratio. MASINGAR mk-2 successfully predicted high aerosol concentrations, but the predicted peak aerosol optical thickness was about one-third of the observed value..
12. Syuichi Itahashi, Hiroshi Hayami, Keiya Yumimoto, Itsushi Uno, Chinese province-scale source apportionments for sulfate aerosol in 2005 evaluated by the tagged tracer method, Environmental Pollution, 10.1016/j.envpol.2016.10.098, 220, 1366-1375, 2017.01, 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 SO42− 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− 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..
13. Keiya Yumimoto, Itsushi Uno, Xiaole Pan, Tomoaki Nishizawa, Sang Woo Kim, Nobuo Sugimoto, Inverse modeling of Asian dust emissions with POPC observations
A TEMM dust sand storm 2014 case study, Scientific Online Letters on the Atmosphere, 10.2151/sola.2017-006, 13, 31-35, 2017.01, An inverse modeling system for estimating Asian dust emissions was developed by combining the GEOS-Chem chemical transport model with the Green's function method. We applied the system to two heavy dust storms that occurred in 2014 (10-25 March and 24 May to 5 June), using surface-based polarization optical particle counter (POPC) observations at Fukuoka. Validation by independent observation datasets, including POPC measurements and PM10 observations at Seoul, showed that the use of a posteriori dust emissions improved overestimations in the a priori simulation and achieved much better agreement with observations. Satellite observations, surface synoptic observations, and modeled wind fields indicated that the major dust source region differed between the two dust storms; the major dust outbreak of one storm occurred in the northeastern Gobi Desert, whereas that of the other occurred in the southern Gobi Desert. The a posteriori dust emissions successfully reproduced this difference. Thus, the inverse modeling system developed in this study was able to improve the estimation of not only the intensity but also the geographical distribution of dust emissions..
14. Itsushi Uno, Keiya Yumimoto, Kazuo Osada, Zhe Wang, Xiaole Pan, Syuichi Itahashi, Shigekazu Yamamoto, Dust acid uptake analysis during long-lasting dust and pollution episodes over East Asia based on synergetic observation and chemical transport model, Scientific Online Letters on the Atmosphere, 10.2151/sola.2017-020, 13, 109-113, 2017.01, Two heavy dust storms that occurred between 24-26 May 2014 in Mongolia and Inner Mongolia, China were responsible for long-lasting dust episodes observed from 26 May to 2 June 2014 in Fukuoka, Japan. During this period, dust and anthropogenic pollutants were transported simultaneously to Fukuoka and Korea and remained there for almost 8 days. We successfully observed fine and coarse aerosol time variations (1-hour intervals) in Fukuoka. The GEOS-Chem chemical transport model, which includes dust-acid uptake processes, successfully reproduced the aerosol variations and explained the Asian-scale dust-pollutant transport and transformation processes. Model sensitivity analyses with and without dust-acid uptake processes showed that the formation of dust-nitrate occurred over the Yellow Sea and East China Sea before arriving in Japan. The model sensitivity analysis showed that less than 5% of the coarse dust-nitrate originated from NOx emissions from Japan, and large amounts of dustnitrate originated outside of Japan..
15. Itsushi Uno, Keiya Yumimoto, Xiaole Pan, Zhe Wang, Kazuo Osada, Syuichi Itahashi, Shigekazu Yamamoto, Simultaneous dust and pollutant transport over East Asia
The Tripartite Environment Ministers Meeting March 2014 case study, Scientific Online Letters on the Atmosphere, 10.2151/sola.2017-009, 13, 47-52, 2017.01, Heavy dust storms that occurred between 13 and 23 March 2014 were selected for analysis as a case study of dust and sand storm events by the Tripartite Environment Ministers Meeting. During this period, two dust and anthropogenic aerosol events were observed and analyzed. The GEOS-Chem chemical transport model, which includes dust-acid uptake processes, successfully reproduced the aerosol variations and explained the Asian-scale dust-pollutant transport processes. Our results confirmed the importance of coarse-mode dust-nitrate as evidence of 'polluted dust' pollution. The model analysis showed that the formation of dust-nitrate occurred over the Yellow Sea and East China Sea before arriving in Japan. We showed that more than 40% of nitrate exists in dust-nitrate when air mass arrived in Japan..
16. Keiya Yumimoto, Yu Morino, Toshimasa Ohara, Yasuji Oura, Mitsuru Ebihara, Haruo Tsuruta, Teruyuki Nakajima, Inverse modeling of the 137Cs source term of the Fukushima Dai-ichi Nuclear Power Plant accident constrained by a deposition map monitored by aircraft, Journal of Environmental Radioactivity, 10.1016/j.jenvrad.2016.06.018, 164, 1-12, 2016.11, The amount of 137Cs released by the Fukushima Dai-ichi Nuclear Power Plant accident of 11 March 2011 was inversely estimated by integrating an atmospheric dispersion model, an a priori source term, and map of deposition recorded by aircraft. An a posteriori source term refined finer (hourly) variations comparing with the a priori term, and estimated 137Cs released 11 March to 2 April to be 8.12 PBq. Although time series of the a posteriori source term was generally similar to those of the a priori source term, notable modifications were found in the periods when the a posteriori source term was well-constrained by the observations. Spatial pattern of 137Cs deposition with the a posteriori source term showed better agreement with the 137Cs deposition monitored by aircraft. The a posteriori source term increased 137Cs deposition in the Naka-dori region (the central part of Fukushima Prefecture) by 32.9%, and considerably improved the underestimated a priori 137Cs deposition. Observed values of deposition measured at 16 stations and surface atmospheric concentrations collected on a filter tape of suspended particulate matter were used for validation of the a posteriori results. A great improvement was found in surface atmospheric concentration on 15 March; the a posteriori source term reduced root mean square error, normalized mean error, and normalized mean bias by 13.4, 22.3, and 92.0% for the hourly values, respectively. However, limited improvements were observed in some periods and areas due to the difficulty in simulating accurate wind fields and the lack of the observational constraints..
17. Keiya Yumimoto, Hiroshi Murakami, Taichu Y. Tanaka, Tsuyoshi T. Sekiyama, Akinori Ogi, Takashi Maki, Forecasting of Asian dust storm that occurred on May 10–13, 2011, using an ensemble-based data assimilation system, Particuology, 10.1016/j.partic.2015.09.001, 28, 121-130, 2016.10, An ensemble-based assimilation system that used the MASINGAR mk-2 (Model of Aerosol Species IN the Global AtmospheRe Mark 2) dust forecasting model and satellite-derived aerosol optical thickness (AOT) data, processed in the JAXA (Japan Aerospace Exploration Agency) Satellite Monitoring for Environmental Studies (JASMES) system with MODIS (Moderate Resolution Imaging Spectroradiometer) observations, was used to quantify the impact of assimilation on forecasts of a severe Asian dust storm during May 10–13, 2011. The modeled bidirectional reflectance function and observed vegetation index employed in JASMES enable AOT retrievals in areas of high surface reflectance, making JASMES effective for dust forecasting and early warning by enabling assimilations in dust storm source regions. Forecasts both with and without assimilation were validated using PM10 observations from China, Korea, and Japan in the TEMM WG1 dataset. Only the forecast with assimilation successfully captured the contrast between the core and tail of the dust storm by increasing the AOT around the core by 70–150% and decreasing it around the tail by 20–30% in the 18-h forecast. The forecast with assimilation improved the agreement with observed PM10 concentrations, but the effect was limited at downwind sites in Korea and Japan because of the lack of observational constraints for a mis-forecasted dust storm due to cloud..
18. Keiya Yumimoto, T. M. Nagao, M. Kikuchi, T. T. Sekiyama, H. Murakami, T. Y. Tanaka, A. Ogi, H. Irie, P. Khatri, H. Okumura, K. Arai, I. Morino, O. Uchino, T. Maki, Aerosol data assimilation using data from Himawari-8, a next-generation geostationary meteorological satellite, Geophysical Research Letters, 10.1002/2016GL069298, 43, 11, 5886-5894, 2016.06, Himawari-8, a next-generation geostationary meteorological satellite, was launched on 7 October 2014 and became operational on 7 July 2015. The advanced imager on board Himawari-8 is equipped with 16 observational bands (including three visible and three near-infrared bands) that enable retrieval of full-disk aerosol optical properties at 10 min intervals from geostationary (GEO) orbit. Here we show the first application of aerosol optical properties (AOPs) derived from Himawari-8 data to aerosol data assimilation. Validation of the assimilation experiment by comparison with independent observations demonstrated successful modeling of continental pollution that was not predicted by simulation without assimilation and reduced overestimates of dust front concentrations. These promising results suggest that AOPs derived from Himawari-8/9 and other planned GEO satellites will considerably improve forecasts of air quality, inverse modeling of emissions, and aerosol reanalysis through assimilation techniques..
19. Tsuyoshi Thomas Sekiyama, Keiya Yumimoto, Taichu Y. Tanaka, Takashi Nagao, Maki Kikuchi, Hiroshi Murakami, Data assimilation of himawari-8 aerosol observations
Asian dust forecast in June 2015, Scientific Online Letters on the Atmosphere, 10.2151/sola.2016-020, 12, 86-90, 2016.01, Himawari-8 is a Japanese geostationary weather satellite that was launched in October 2014 and has been in operation since July 2015. Himawari-8 is equipped with an outstanding highperformance imager that has 16 spectral channels (3 for visible, 3 for near-infrared and 10 for infrared wavelengths) with a 10- minute observation interval. We retrieved aerosol optical thickness (AOT) from visible and near-infrared multispectral observations of Himawari-8 and assimilated the AOT data into a global aerosol forecast model with an ensemble Kalman filter system. The data assimilation result was validated by comparison with conventional products derived from polar-orbiting satellite aerosol observations (i.e., Moderate Resolution Imaging Spectroradiometer (MODIS) AOT) of an Asian dust storm in June 2015. The Himawari-8 AOT data assimilation successfully produced an analysis and forecast of the Asian dust that was comparable or superior to those of the MODIS AOT data assimilation. The Himawari-8 aerosol product has a much higher temporal coverage than that of polar-orbiting satellites, which is promising for aerosol data assimilation. This study is a first step in the application of geostationary satellites for aerosol research..
20. Keiya Yumimoto, Toshihiko Takemura, Long-term inverse modeling of Asian dust
Interannual variations of its emission, transport, deposition, and radiative forcing, Journal of Geophysical Research, 10.1002/2014JD022390, 120, 4, 1582-1607, 2015.02, Inverse modeling of Asian dust over the 8-year period 2005-2012 was performed with the Spectral Radiation-Transport Model for Aerosol Species/four-dimensional variational (SPRINTARS/4D-Var) data assimilation system and satellite-measured aerosol optical thickness over the ocean. We validated the inversion results with independent measurements provided by ground-based and space-based lidar and various in situ measurements. The inversion results were used to analyze interannual variations of Asian dust fluxes and relationships of these fluxes with climate indices. Dust emissions from central China and the Mongolian Plateau were 229-384-Tg-yr-1. The standard deviation of 55.3-Tg-yr-1 reflected large interannual variability. The frequency of dust storms and the beginning of the dust season in the source region also showed interannual variations. There was a meridional shift of the outflow path from the continent; the transport core was centered at 40-45°N during southern transport years (2006-2007) and at 35-40°N during northern transport years (2005 and 2008-2012). The fact that dust deposition showed a significant positive correlation with satellite-measured chlorophyll concentrations indicated that settled Asian dust enhanced phytoplankton blooms in the eastern North Pacific. Dust emissions were positively and negatively correlated with the Far Eastern Zonal and Dynamical Normalized Seasonality indices, respectively, the implication being that a strong meridional pressure gradient over the source region and a strong winter monsoon favor dust emission. The fact that the Southern Oscillation Index was positively correlated with dust emission, transport, and deposition suggests that Asian dust is affected by the El Niño-Southern Oscillation cycle and is enhanced during the La Niña phase. Key Points Long-term inverse modeling of Asian dust was performed for the period 2005-2012 Interannual variability of Asian dust was analyzed with the inversion results The relationship between Asian dust and climate indices was also investigated.
21. Keiya Yumimoto, Itsushi Uno, Syuichi Itahashi, Long-term inverse modeling of Chinese CO emission from satellite observations, Environmental Pollution, 10.1016/j.envpol.2014.07.026, 195, 308-318, 2014.12, Carbon monoxide (CO) emissions in China in 2005-2010 were estimated by inversion, using the Green's function method from vertical CO profiles derived from MOPITT Version 5 satellite data and a tagged CO simulation, and validated with independent in situ observations from the World Data Centre for Greenhouse Gases. Modeling with a posteriori emission successfully reproduced CO outflow from the continent to the East China Sea, Sea of Japan, and Japanese islands during winter and spring, and compensated for underestimates in central and eastern China in summer. A posteriori emissions showed large seasonal variations in which December and March emissions were on average 23% larger than August emissions, consistent with other studies. Estimated Chinese CO emissions were 184.4, 173.1, 184.6, 158.4, 157.4, and 157.3 Tg/year for 2005-2010, respectively. The decrease after 2007 is partly attributed to Chinese socioeconomic conditions and improved combustion efficiency..
22. Itsushi Uno, Nobuo Sugimoto, Atsushi Shimizu, Keiya Yumimoto, Yukari Hara, Zifa Wang, Record heavy PM2.5 air pollution over China in January 2013
Vertical and horizontal dimensions, Scientific Online Letters on the Atmosphere, 10.2151/sola.2014-028, 10, 1, 136-140, 2014.01, Record heavy PM2.5 air pollution (maximum concentration of ∼1 mg m-3) observed over China in January 2013 was analyzed. The vertical and horizontal scales of the pollution layer are critically important parameters for the analysis of pollution phenomena, but they are difficult to measure. This is because the PM2.5 aerosol concentration is so high that ordinary remote-sensing methods such as ground-based and space-borne lidar inversion are difficult to apply. First, we showed the detailed time-height structure of aerosol extinction coefficients based on Beijing lidar observation, by assuming a non-zero boundary extinction coefficient and using 3D chemical transport modeling (CTM). The aerosol structure derived from lidar observations and the CTM results were in close agreement. Using ground-based lidar, we also found that a shallow aerosol layer (height of 200-300 m) remained over Beijing for a long time. We also successfully showed that the horizontal extent of the aerosol layer over the China Plain was several hundred km based on CALIOP observations and CTM..
23. Keiya Yumimoto, Toshihiko Takemura, The SPRINTARS version 3.80/4D-Var data assimilation system
Development and inversion experiments based on the observing system simulation experiment framework, Geoscientific Model Development, 10.5194/gmd-6-2005-2013, 6, 6, 2005-2022, 2013.11, We present an aerosol data assimilation system based on a global aerosol climate model (SPRINTARS - Spectral Radiation-Transport Model for Aerosol Species) and a four-dimensional variational data assimilation method (4D-Var). Its main purposes are to optimize emission estimates, improve composites, and obtain the best estimate of the radiative effects of aerosols in conjunction with observations. To reduce the huge computational cost caused by the iterative integrations in the models, we developed an offline model and a corresponding adjoint model, which are driven by pre-calculated meteorological, land, and soil data. The offline and adjoint model shortened the computational time of the inner loop by more than 30%. By comparing the results with a 1 yr simulation from the original online model, the consistency of the offline model was verified, with correlation coefficient R > 0.97 and absolute value of normalized mean bias NMB < 7% for the natural aerosol emissions and aerosol optical thickness (AOT) of individual aerosol species. Deviations between the offline and original online models are mainly associated with the time interpolation of the input meteorological variables in the offline model; the smaller variability and difference in the wind velocity near the surface and relative humidity cause negative and positive biases in the wind-blown aerosol emissions and AOTs of hygroscopic aerosols, respectively. The feasibility and capability of the developed system for aerosol inverse modelling was demonstrated in several inversion experiments based on the observing system simulation experiment framework. In the experiments, we used the simulated observation data sets of fine- and coarse-mode AOTs from sun-synchronous polar orbits to investigate the impact of the observational frequency (number of satellites) and coverage (land and ocean), and assigned aerosol emissions to control parameters. Observations over land have a notably positive impact on the performance of inverse modelling as compared with observations over ocean, implying that reliable observational information over land is important for inverse modelling of land-born aerosols. The experimental results also indicate that information that provides differentiations between aerosol species is crucial to inverse modelling over regions where various aerosol species coexist (e.g. industrialized regions and areas downwind of them)..
24. Keiya Yumimoto, Impacts of geostationary satellite measurements on CO forecasting
An observing system simulation experiment with GEOS-Chem/LETKF data assimilation system, Atmospheric Environment, 10.1016/j.atmosenv.2013.03.032, 74, 123-133, 2013.08, We developed a chemical data assimilation system based on the GEOS-Chem global chemical transport model (CTM) and an ensemble-based data assimilation method, and performed an observing system simulation experiment (OSSE) to evaluate the impact of geostationary (GEO) satellite data obtained with a multi-spectral (thermal infrared (TIR) and near infrared (NIR)) sensor on air quality forecasting in East Asia.Initial conditions determined by assimilation of the three observation sets improved the forecasting of trans-boundary CO outflow. The performance of GEO satellite with TIR sensor (GEO-TIR) was better than that of LEO satellite with TIR sensor (LEO-TIR). However, in Seoul district (the Korean Peninsula) and Northern Kyushu (western Japan), the positive impact of the wider coverage and higher frequency of GEO disappeared when the forecast time was longer than 48h. GEO satellite with NIR and TIR sensor (GEO-NIR+TIR) improved the forecast most, reducing the root mean square difference (RMSD), normalized mean bias, and normalized mean difference by more than 20% even for a forecast time longer than 48h.Using the LEO-TIR result as a benchmark, we evaluated the ability of GEO-NIR+TIR to improve the forecast. The 60-hCO forecasting performances of GEO-TIR and GEO-NIR+TIR were about 30% and 120% better, respectively, than that of LEO-TIR. The wider coverage and higher frequency of GEO therefore improved the RMSD by 30%, and the higher sensitivity in the lower troposphere of NIR+TIR improved it by an additional 90%. Thus, the higher sensitivity in the lower troposphere of NIR+TIR as well as the wider coverage and higher frequency of GEO had a notably positive impact on the forecasting of trans-boundary pollutants over East Asia..
25. S. Itahashi, Itsushi Uno, Keiya Yumimoto, H. Irie, K. Osada, K. Ogata, H. Fukushima, Z. Wang, T. Ohara, Interannual variation in the fine-mode MODIS aerosol optical depth and its relationship to the changes in sulfur dioxide emissions in China between 2000 and 2010, Atmospheric Chemistry and Physics, 10.5194/acp-12-2631-2012, 12, 5, 2631-2640, 2012.12, Anthropogenic SO2emissions increased alongside economic development in China at a rate of 12.7%yr-1from 2000 to 2005. However, under new Chinese government policy, SO2emissions declined by 3.9%yr-1 between 2005 and 2009. Between 2000 and 2010, we found that the variability in the fine-mode (submicron) aerosol optical depth (AOD) over the oceans adjacent to East Asia increased by 3-8% yr-1to a peak around 2005-2006 and subsequently decreased by 2-7% yr-1, based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA's Terra satellite and simulations by a chemical transport model. This trend is consistent with ground-based observations of aerosol particles at a mountainous background observation site in central Japan. These fluctuations in SO2 emission intensity and fine-mode AOD are thought to reflect the widespread installation of fuel-gas desulfurization (FGD) devices in power plants in China, because aerosol sulfate is a major determinant of the fine-mode AOD in East Asia. Using a chemical transport model, we confirmed that the contribution of particulate sulfate to the fine-mode AOD is more than 70% of the annual mean and that the abovementioned fluctuation in fine-mode AOD is caused mainly by changes in SO2emission rather than by other factors such as varying meteorological conditions in East Asia. A strong correlation was also found between satellite-retrieved SO2vertical column density and bottom-up SO2 emissions, both of which were also consistent with observed fine-mode AOD trends. We propose a simplified approach for evaluating changes in SO2 emissions in China, combining the use of modeled sensitivity coefficients that describe the variation of fine-mode AOD with changes in SO2 emissions and satellite retrieval. Satellite measurements of fine-mode AOD above the Sea of Japan marked a 4.1%yr -1 decline between 2007 and 2010, which corresponded to the 9% yr-1 decline in SO2emissions from China during the same period..
26. Keiya Yumimoto, Itsushi Uno, N. Sugimoto, A. Shimizu, Yukari Hara, Toshihiko Takemura, Size-resolved adjoint inversion of Asian dust, Geophysical Research Letters, 10.1029/2012GL053890, 39, 24, 2012.12, We expanded the variational assimilation system of a regional dust model by using size-resolved inversion. Dust emissions and particle-size distributions of a severe dust and sandstorm (DSS) in April 2005 were inversely optimized with optical measurements by the National Institute for Environmental Studies lidar network. The inversion results successfully compensated underestimates by the original model and increased the ngstrm exponent around the DSS core by 13-17%, shifting the particle-size distribution to finer. The a posteriori size distribution was distinctly different between eastern and western source regions. In the western regions, dust emissions in the 3.19 and 5.06 m size bins increased considerably, and the peak size shifted from 5.06 to 3.19 m, whereas in the eastern regions, emissions of finer particles (bins 0.82-2.01 m) increased. Differences in vegetation and soil type and moisture between eastern and western regions might explain the characteristics of the inverted size distribution..
27. Keiya Yumimoto, Toshihiko Takemura, Direct radiative effect of aerosols estimated using ensemble-based data assimilation in a global aerosol climate model, Geophysical Research Letters, 10.1029/2011GL049258, 38, 21, 2011.11, We developed a new ensemble-based data-assimilation system based on a global aerosol climate model and performed a 1-month assimilation experiment using satellite optical measurements from MODIS onboard TERRA and AQUA to estimate the direct radiative effect (DRE) of aerosols. Using the assimilated data field, monthly averaged optical thickness (AOT) was estimated to be 0.15 ± 0.030 (a 52.0% increase over a priori), and the root mean-square difference (RMSD) between modeled values and MODIS measurements was reduced by 28.4%. Independent validation using globally distributed AERONET measurements showed that the a posteriori data achieved better agreement with 82.5% of 80 AERONET sites. However, improvements in ngstrm exponents were limited (50.0% of sites). Using the assimilated aerosol field, we modeled the aerosol DRE. A posteriori whole-and clear-sky DREs at the top of the atmosphere were estimated to be-1.1 ± 0.35 and-2.5 ± 0.49 W/m2, respectively, in May 2007 and were close to previously reported measurement-based estimates..
28. Itsushi Uno, K. Eguchi, Keiya Yumimoto, Z. Liu, Yukari Hara, N. Sugimoto, A. Shimizu, Toshihiko Takemura, Large Asian dust layers continuously reached North America in April 2010, Atmospheric Chemistry and Physics, 10.5194/acp-11-7333-2011, 11, 14, 7333-7341, 2011.07, The NASA space-borne Mie-lidar system CALIPSO/CALIOP revealed that multiple large Asian dust layers with a horizontal scale of 2000-3000 km reached North America, occupying the full troposphere, in April 2010. This kind of dust layer transport has not been reported before. Our analysis of CALIOP data and global aerosol model results revealed that frequent dust emissions occurred in northwestern China because of stronger-than-average near-surface winds, and that strong stable westerly winds carried the Asian dust from northwestern China to the central Pacific Ocean. A negative pressure anomaly was located in the eastern Pacific Ocean, and the main dust transport path was split into two branches: a northern path and a southern path over North America. Northern-path dust was trapped and stagnant for a longer time than southern path dust and finally subsided under a high-pressure system. Dust along the southern path reached the central US. These complex conditions resulted in a multi-layered structure of dust over North America..
29. Yukari Hara, Itsushi Uno, Atsushi Shimizu, Nobuo Sugimoto, Ichiro Matsui, Keiya Yumimoto, Jun Ichi Kurokawa, Toshimasa Ohara, Zhaoyan Liu, Seasonal characteristics of spherical aerosol distribution in eastern Asia
Integrated analysis using ground/space-based lidars and a chemical transport model, Scientific Online Letters on the Atmosphere, 10.2151/sola.2011-031, 7, 1, 121-124, 2011.07, Seasonal characteristics of spherical aerosol distributions in eastern Asia were investigated between July 2006 and December 2008 using data from ground-based and space-borne lidar observations and the Community Multi-scale Air Quality Modeling System (CMAQ) chemical transport model simulation. The seasonal variation of spherical aerosol optical thickness (AOT) observed at four ground lidar stations surrounding the East China Sea (Beijing, Guangzhou, Seoul, and Hedo/Okinawa) was generally consistent with CMAQ simulation results. Detailed analyses confirmed clear regional differences in aerosol compositions. Analyses of aerosol vertical profiles revealed that the spherical aerosol variation is greatest in Beijing, with scale height varying between 720 m and 2100 m. The analyses also revealed that the seasonal variation patterns of spherical AOT are classifiable into 'summer peak' and 'summer trough' types. Northern sites (Beijing and Seoul) are of the summer peak type; southern sites (Guangzhou and Okinawa) show the summer trough pattern. Our analyses demonstrated that the Asian summer-winter monsoon system plays a major role in regulating such seasonal variation. The CMAQ simulated variation of spherical aerosols is well correlated to the synoptic scale monsoon variation..
30. Paulo H R Calil, Scott C. Doney, Keiya Yumimoto, Kenta Eguchi, Toshihiko Takemura, Episodic upwelling and dust deposition as bloom triggers in low-nutrient, low-chlorophyll regions, Journal of Geophysical Research, 10.1029/2010JC006704, 116, 6, 2011.06, Summertime phytoplankton blooms in the oligotrophic North Pacific Ocean are supported by N2-fixing organisms that relieve the system of nitrate limitation. Phosphate and iron, however, limit their growth and need to be supplied for these organisms to thrive. We analyze two recent blooms in the region whose differences provide insight into their possible formation mechanisms. In 2008, a typical late summer bloom, with sporadic patches of higher-chlorophyll concentration, occurred near the island chain and the subtropical front. In 2010, an unusually large, contiguous bloom was observed in the western oligotrophic North Pacific, a region where blooms seldom, if ever, occur. Streaks of high chlorophyll in 2008 coincide with surface temperature fronts and regions of large horizontal stretching, as detected by Lagrangian diagnostics. Such regions are prone to the generation of vertical velocities via frontogenesis. Horizontal transport from upwelling regions or iron-rich island sediments is also important for the redistribution of nutrients. In the case of the 2010 bloom, we use a global aerosol transport model as well as space-borne lidar observations to argue that atmospheric dust deposition events prior to the bloom provided the necessary nutrient conditions for the growth of N 2-fixing organisms. As sea surface temperature increased in the region, chlorophyll values increased significantly, showing that this bloom was likely a consequence of prior enrichment and that temperature is a key factor in bloom development in this important biome..
31. Kenta Eguchi, Itsushi Uno, Keiya Yumimoto, Toshihiko Takemura, Takashi Y. Nakajima, Mitsuo Uematsu, Zhaoyan Liu, Modulation of cloud Droplets and radiation over the North Pacific by sulfate aerosol erupted from Mount Kilauea, Scientific Online Letters on the Atmosphere, 10.2151/sola.2011-020, 7, 1, 77-80, 2011.06, Mount Kilauea in the Hawaiian Islands experienced an active eruption from March until the end of December 2008 and showed a large-scale impact on aerosol, cloud microphysical properties and atmospheric radiation over the North Pacific. We analyzed the atmospheric impact of this eruption based on the satellite retrievals and 3-D global chemistry-radiation coupled transport model. We showed that approximately 1.8 Tg (±1.2 Tg) release of SO2 was estimated from this eruption, which oxidized into sulfate aerosol during transport to the northwest Pacific Ocean. The volcanic sulfate aerosol layer covering a large area (~6.5 × 106 km2) of the lower troposphere over the North Pacific for several months was confirmed from both satellite and model results. Sulfate aerosols affected the formation of cumulus water clouds by reducing the typical cloud effective radius by ~23% and increasing the cloud fractional coverage over the ocean from 9.1% to 13.4% (over the region 170°E-160°W, 10°N-20°N). The affected cumulus clouds appeared whiter than normal and thus reflected more solar radiation. Consequently, satellite observations revealed an approximately 1% increase in albedo at the top of the atmosphere in the area along main volcano plume trajectory, which induced an approximately -5 W m-2 change in the shortwave radiation budget..
32. Seung Bum Kim, Keiya Yumimoto, Itsushi Uno, Youngsin Chun, Dust Model Intercomparison Between ADAM and CFORS/Dust For Asian Dust Case in 2007 (March 28 - April 3), Scientific Online Letters on the Atmosphere, 10.2151/sola.7A-007, 7, A, 25-28, 2011.03, As one of research activities of the Joint Research on Dust and Sand Storms (DSS) among China, Korea and Japan, intercomparison between two operational dust forecasting models (ADAM and CFORS/Dust) has been conducted using the selected DSS case which occurred in 2007. The results of simulations by both models were compared with various observations such as surface PM10, Aerosol Optical Thickness, and dust extinction coefficient. In general, both models produced similar results and the predicted values matched well with the observations, despite differences in emission treatment, the adoption of data assimilation technique, and meteorological inputs. However, a large difference (up to 4 times) in modeled surface PM10 concentrations between the models was observed at sites located in source or near-source regions. For the selected case, the dust emission amount calculated by ADAM was larger than that by CFORS/Dust. The vertical structure of dust layer from the models was different due to the characteristics of meteorological inputs used for each model. This study suggests that the construction of more accurate dust source allocation scheme, comprehensive dust emission treatment, improved meteorological inputs and the development of dust data assimilation technique with various dust observations are required for building a more accurate early-warning system of DSS in East Asia..
33. Nobuo Sugimoto, Yukari Hara, Atsushi Shimizu, Keiya Yumimoto, Itsushi Uno, Masataka Nishikawa, Comparison of surface observations and a regional dust transport model assimilated with lidar network data in Asian dust event of March 29 to April 2, 2007, Scientific Online Letters on the Atmosphere, 10.2151/sola.7A-004, 7, A, 13-16, 2011.02, Surface observation data taken in Mongolia, China, Korea and Japan during the Asian dust event of March 29 to April 2, 2007 were compared with a regional dust transport model assimilated with the lidar network data. The assimilated model reproduced the reported dust event in Mongolia and the observed PM10 concentrations in Korea and Japan very well. The mass/extinction conversion factor (MEF) obtained from the lidar dust extinction coefficient and PM10 concentration was also compared with the assimilated model for Seoul and Tsukuba where both the lidar and PM10 data were available. The MEFs for PM10 and PM2.5 (the ratio of dust-only PM10 or PM2.5 to the dust extinction coefficient) were calculated with the assimilated model. The modeled MEF for PM10 reproduced the observed MEF reasonably and exhibited spatial and temporal variations reflecting the variations in the dust particle size distribution. The modeled MEF for PM2.5 had much less variation. This indicates that the dust extinction coefficient has a higher correlation with dust PM2.5 and should be a useful index for studying the effect of dust on human health..
34. Yoko Iwamoto, Keiya Yumimoto, Mitsuhiro Toratani, Atsushi Tsuda, Kazuhiko Miura, Itsushi Uno, Mitsuo Uematsu, Biogeochemical implications of increased mineral particle concentrations in surface waters of the northwestern North Pacific during an Asian dust event, Geophysical Research Letters, 10.1029/2010GL045906, 38, 1, 2011.01, Simultaneous observations were made in the marine atmospheric boundary layer and surface ocean during spring 2007 to investigate potential impacts of Asian dust on a semi-pelagic region of the northwestern North Pacific. The results suggest that mineral dust aerosols were scavenged by sea fog, and their deposition to the ocean increased the particle concentration in surface seawater. The atmospheric input of mineral dust to the ocean surface from this event was calculated to be 40 to 680 mg m-2 event-1. A general relationship for the solubility of iron from dust particles led to an estimate of 20 to 330 g m-2 for the amount of bio-available iron delivered during the dust event. This input of bio-available iron is comparable to total dissolved iron added during an iron fertilization experiment in the northwestern North Pacific in which an enhancement of primary production was observed..
35. Syuichi Itahashi, Keiya Yumimoto, Itsushi Uno, Kenta Eguchi, Toshihiko Takemura, Yukari Hara, Atsushi Shimizu, Nobuo Sugimoto, Zhaoyan Liu, Structure of dust and air pollutant outflow over East Asia in the spring, Geophysical Research Letters, 10.1029/2010GL044776, 37, 20, 2010.10, Springtime outflow of Asian dust and air pollutants was investigated by a synergetic analysis of ground-based/space-borne Lidar observations and numerical models. We identified two prominent outflow patterns, and its occurrence frequency. Pattern I was induced within a typical warm-sector which lifted up dust particles into the free troposphere, and the existence of two sequential low-pressure systems played an important role. Pattern II was a behind cold front outbreak. Atmospheric stratification was significantly different; Pattern I had weak stratification within the troposphere (potential temperature gradient of ∼2-3.4 K/km), and most of elevated dust layer (typically horizontally 1500-2000 km, vertically 2.5-4 km AGL) remained unmixed with pollutants. Pattern II was characterized by a strong stratification of ∼5 K/km; dust and pollutants were trapped and well mixed within the PBL, forming polluted dust. Among the six cases of large-scale dust/pollutants outbreaks, only two cases are belonged to Pattern I..
36. Keiya Yumimoto, K. Eguchi, Itsushi Uno, Toshihiko Takemura, Z. Liu, A. Shimizu, N. Sugimoto, K. Strawbridge, Summertime trans-Pacific transport of Asian dust, Geophysical Research Letters, 10.1029/2010GL043995, 37, 18, 2010.09, In mid-August 2009, ground-based lidar networks on both sides of the Pacific Basin detected an elevated dust layer. A combined analysis by ground-based lidars, space-borne lidar CALIOP, and numerical models revealed that dust particles emitted in the Taklimakan Desert were transported across the Pacific Ocean in 12 to 13 days. This was the first evidence of summertime trans-Pacific transport of Asian dust from the Taklimakan Desert. A large-scale dust storm occurred in the Taklimakan Desert during 12-16 August due to a strong surface wind accompanied by a cold front. Many dust particles were lifted up into the free atmosphere by the upslope wind formed by the steep slope of the surrounding mountains. This dust injection process was analogous to that for springtime cases. The Taklimakan dust was then transported eastward at 6-8 km altitude. This high transport altitude allowed the Taklimakan Dust to be transported beyond the Pacific Ocean without the effect of the southeasterly outflow of the summertime Pacific high. The wind field anomaly at 500 hPa in mid-August 2009 shows increases of northwesterly winds driven by SE-NW pressure gradients around 110-140°E and 180-140°W, indicating that the pressure pattern during the dust event favored the trans-Pacific transport..
37. Nobuo Sugimoto, Yukari Hara, Keiya Yumimoto, Itsushi Uno, Masataka Nishikawa, Jugder Dulam, Dust emission estimated with an assimilated dust transport model using lidar network data and vegetation growth in the gobi desert in Mongolia, Scientific Online Letters on the Atmosphere, 10.2151/sola.2010-032, 6, 1, 125-128, 2010.09, Dust emission estimated with a 4D-Var data assimilation system using ground-based lidar network data was compared with vegetation growth data based on visual observations in the Gobi desert in Mongolia in the spring of 2007. The dust emission flux estimated with the data assimilation system was less than that estimated without data assimilation in the dust event of May 21-30 and was the opposite in the event of March 25-April 3. The threshold surface friction velocity estimated from the results of the data assimilation was less than 0.3 m s-1 in the dust event of March 25-April 3 and was ~0.36 m s-1 in the event of May 21-30. The difference between the two events was qualitatively explained by the vegetation growth data. The accumulated precipitation during the period was ~2 mm. The results show that vegetation growth with slight precipitation in the Gobi desert may significantly reduce dust emission..
38. Keiya Yumimoto, K. Eguchi, Itsushi Uno, Toshihiko Takemura, Z. Liu, A. Shimizu, N. Sugimoto, An elevated large-scale dust veil from the Taklimakan Desert
Intercontinental transport and three-dimensional structure as captured by CALIPSO and regional and global models, Atmospheric Chemistry and Physics, 10.5194/acp-9-8545-2009, 9, 21, 8545-8558, 2009.11, An intense dust storm occurred during 19ĝ€"20 May 2007 over the Taklimakan Desert in northwestern China. Over the following days, the space-borne lidar CALIOP tracked an optically thin, highly elevated, horizontally extensive dust veil that was transported intercontinentally over eastern Asia, the Pacific Ocean, North America, and the Atlantic Ocean. A global aerosol transport model (SPRINTARS) simulated the dust veil quite well and provided a three-dimensional view of the intercontinental dust transport. The SPRINTARS simulation revealed that the dust veil traveled at 4ĝ€"10 km altitudes with a thickness of 1ĝ€"4 km along the isentropic surface between 310 and 340 K. The transport speed was about 1500 km/day. The estimated dust amount exported to the Pacific was 30.8 Gg, of which 65% was deposited in the Pacific and 18% was transported to the North Atlantic. These results imply that dust veils can fertilize open oceans, add to background dust, and affect the radiative budget at high altitudes through scattering and absorption.

The injection mechanism that lifts dust particles into the free atmosphere is important for understanding the formation of the dust veil and subsequent long-range transport. We used a regional dust transport model (RC4) to analyze the dust emission and injection over the source region. The RC4 analysis revealed that strong northeasterly surface winds associated with low pressures invaded the Taklimakan Desert through the eastern corridor. These winds then formed strong upslope wind along the high, steep mountainsides of the Tibetan Plateau and blew large amounts of dust into the air. The updraft lifted the dust particles farther into the upper troposphere (about 9 km above mean sea level, MSL), where westerlies are generally present. The unusual terrain surrounding the Taklimakan Desert played a key role in the injection of dust to the upper troposphere to form the dust veil..
39. Itsushi Uno, Kenta Eguchi, Keiya Yumimoto, Toshihiko Takemura, Atsushi Shimizu, Mitsuo Uematsu, Zhaoyan Liu, Zifa Wang, Yukari Hara, Nobuo Sugimoto, Asian dust transported one full circuit around theglobe, Nature Geoscience, 10.1038/ngeo583, 2, 8, 557-560, 2009.08, Mineral dust is usually transported long distances in the lower troposphere. There are examples of Asian dust being transported across the Pacific Ocean, and traces of Asian dust have also been found in ice and snow cores in Greenland and the French Alps. Here, we use measurements from the Cloud-Aerosol Lidar with Orthogonal Polarization, an air parcel trajectory model and a three-dimensional aerosol transport model to map the transport of dust clouds generated during a storm in Chinas Taklimakan Desert during May 2007. We show that the dust-veiled clouds were lofted to the upper troposphere around 8-10 km above the Earths surface and transported more than one full circuit around the globe in about 13 days. When the dust reached the northwestern Pacific Ocean for the second time, the subsidence of a large-scale high-pressure system caused it to descend into the lower troposphere; some of the dust was then deposited over the ocean. Our analysis also indicates that the dust particles may have acted as ice nuclei in these high-altitude clouds, leading to the formation of cirrus clouds. We suggest that Asian dust can influence the global radiation budget by stimulating cirrus cloud formation and marine ecosystems by supplying nutrients to the open ocean..
40. K. Eguchi, Itsushi Uno, Keiya Yumimoto, Toshihiko Takemura, A. Shimizu, N. Sugimoto, Z. Liu, Trans-pacific dust transport
Integrated analysis of NASA/CALIPSO and a global aerosol transport model, Atmospheric Chemistry and Physics, 10.5194/acp-9-3137-2009, 9, 9, 3137-3145, 2009.05, Detailed 3-D structures of Trans-Pacific Asian dust transport occurring during 5-15 May 2007 were investigated using the NASA/CALIOP vertical-resolved measurements and a three-dimensional aerosol model (SPRINTARS). Both CALIOP and SPRINTARS dust extinctions showed a good agreement along the way of the transport from the dust source regions across North Pacific into North America. A vertically two-layered dust distribution was observed over the northeastern Pacific and North America. The lower dust layer originated from a dust storm generated in the Gobi Desert on 5 May. It was transported at an altitude of around 4 km MSL and has mixed with Asian anthropogenic air pollutants during the course of transport. The upper dust layer mainly originated from a dust storm that occurred in the Taklimakan Desert 2-3 days after the Gobi dust storm generation. The upper dust cloud was transported in higher altitudes above the major clouds layer during the Trans-Pacific transport. It therefore has remained unmixed with the Asian air pollutants and almost unaffected by wet removal. The decay of its concentration level was small (only one-half after its long-distance transport crossing the Pacific). Our dust budget analysis revealed that the Asian dust flux passing through the longitude plane of 140° E was 2.1 Tg, and one third of that arrived North America. The cases analyzed in this study revealed that, while the Gobi Desert is an important source that can contribute to the long-range dust transport, the Taklimakan Desert appears to be another important source that can contribute to the dust transport occurring particularly at high altitudes..
41. Jun ichi Kurokawa, Keiya Yumimoto, Itsushi Uno, Toshimasa Ohara, Adjoint inverse modeling of NOx emissions over eastern China using satellite observations of NO2 vertical column densities, Atmospheric Environment, 10.1016/j.atmosenv.2008.12.030, 43, 11, 1878-1887, 2009.04, A four-dimensional variational data assimilation system for optimization of NOx emissions (RC4-NOx) was developed. A parameterized NOx chemistry scheme was introduced into the RC4-NOx system, and key parameters such as chemical production and loss terms of NOx were calculated in advance using the Community Multiscale Air Quality (CMAQ) modeling system. RC4-NOx was applied to optimize NOx emissions over eastern China (EC) in July 1996, 1999, and 2002 using Global Ozone Monitoring Experiment (GOME) satellite observations of NO2 vertical column densities (VCDs) and a priori emissions from the Regional Emission Inventory in Asia (REAS). After assimilation, RC4-NOx generally reproduced the spatial distribution, regional averaged values, and time evolution of GOME NO2 VCDs. Over EC, a priori emissions were reduced by 20% in 1996 and by 8% in 1999, whereas a posteriori emissions were almost the same as a priori emissions in 2002. A priori emissions in the Beijing region were reduced by optimization over the whole simulation period. A posteriori emissions over the Yangtze Delta were larger than a priori emissions in 2002, although they were smaller in both 1996 and 1999. As in other areas, a priori emissions over the North China Plain were reduced in 1996; but those over the eastern part of the plain were increased in 1999, and the area of increased emissions moved slightly westward in 2002. In each region, the growth rates of a posteriori emissions during both 1996-1999 and 1999-2002 became generally larger than those of a priori emissions, and the trends of a posteriori emissions became similar to those of GOME NO2 VCDs. Our inverse modeling analysis indicates that the rate of increase of NOx emissions over EC from 1996 to 2002 was much larger for a posteriori emissions (49%) than for a priori emissions (19%)..
42. Yukari Hara, Keiya Yumimoto, Itsushi Uno, A. Shimizu, N. Sugimoto, Z. Liu, D. M.Winker, Asian dust outflow in the PBL and free atmosphere retrieved by NASA CALIPSO and an assimilated dust transport model, Atmospheric Chemistry and Physics, 9, 4, 1227-1239, 2009.02, Three-dimensional structures of Asian dust transport in the planetary boundary layer (PBL) and free atmosphere occurring successively during the end of May 2007 were clarified using results of space-borne backscatter lidar, Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), and results obtained using a data-assimilated version of a dust transport model (RC4) based on a groundbased NIES lidar network. The dust layer depths and the vertical and horizontal structure simulated by RC4 agreed with those of CALIOP observations from the dust source region to the far-downstream region. Two important transport mechanisms of Asian dust in the PBL and free atmosphere were clarified: a low-level dust outbreak within the dry slot region of a well-developed low-pressure system, and formation of an elevated dust layer within the warm sector of a low-pressure system. We also represent the aging of pure dust particles using the particle depolarization ratio (PDR) at 532 nm and the color ratio (CR) at 1064 nm and 532 nm. Aerosols with high PDR were observed uniformly over the dust source region. While the dust cloud was transported to the eastern downwind regions, aerosols with low PDR and high CR occur in the layer of less than 1 km height, suggesting a mixing state of spherical aerosols and dust in the surface layer..
43. Yukari Hara, Itsushi Uno, Keiya Yumimoto, M. Tanaka, A. Shimizu, N. Sugimoto, Z. Liu, Summertime taklimakan dust structure, Geophysical Research Letters, 10.1029/2008GL035630, 35, 23, 2008.12, Vertical dust structures and meteorological conditions over the Taklimakan Desert during the summertime periods (July-September) in 2006 and 2007 were investigated using satellite data including the CALIPSO lidar (CALIOP) measurements and the Weather Research and Forecasting (WRF) model simulation. Summertime convective velocity simulated by WRF was greater than 3 m/s, and the convective time scale was about 1000 s (ca. 15 min). We examined 42 CALIPSO paths (24 daytime and 18 nighttime paths) of data acquired under convective dusty conditions. The dust layer thickness derived from the CALIOP measurements reaches 3000-4000 m, which is approximately equal to the Tarim Basin depth. This thickness shows a good correlation with the WRF simulated depth of the convective boundary layer (BL). The dust remains suspended during both daytime and nighttime; the CALIOP average dust extinction coefficients in the BL are respectively 0.151 ± 0.102 km-1 and 0.128 ± 0.079 km-1 for daytime and nighttime. Finally, we estimated the dust amount transported from the BL to the free atmosphere. Typically, 10-20 Gg/day of dust (assuming area of 600 km × 300 km as a main part of the Taklimakan Desert) is transported from the Taklimakan Desert by vertical mixing. The daily horizontal dust flux above the BL was estimated to be 40-50 Gg/day over the Taklimakan Desert..
44. H. Tanimoto, Y. Sawa, S. Yonemura, Keiya Yumimoto, H. Matsueda, Itsushi Uno, T. Hayasaka, H. Mukai, Y. Tohjima, K. Tsuboi, L. Zhang, Diagnosing recent CO emissions and ozone evolution in East Asia using coordinated surface observations, adjoint inverse modeling, and MOPITT satellite data, Atmospheric Chemistry and Physics, 8, 14, 3867-3880, 2008.07, Simultaneous ground-based measurements of ozone (O3) and carbon monoxide (CO) were conducted in March 2005 as part of the East Asian Regional Experiment (EAREX) 2005 under the umbrella of the Atmospheric Brown Clouds (ABC) project. Multiple air quality monitoring networks were integrated by performing intercomparison of individual calibration standards and measurement techniques to ensure comparability of ambient measurements, along with providing consistently high time-resolution measurements of O3 and CO at the surface sites in East Asia. Ambient data collected from eight surface stations were compared with simulation results obtained by a regional chemistry transport model to infer recent changes in CO emissions from East Asia. Our inverse estimates of the CO emissions from China up to 2005 suggested an increase of 16% since 2001, in good agreement with the recent MOPITT satellite observations and the bottom-up estimates up to 2006. The O3 enhancement relative to CO in continental pollution plumes traversed in the boundary layer were examined as a function of transport time from the Asian continent to the western Pacific Ocean. The observed ΔO3/ΔCO ratios show increasing tendency during eastward transport events due likely to en-route photochemical O3 formation, suggesting that East Asia is an important O3 source region during spring..
45. Keiya Yumimoto, Itsushi Uno, N. Sugimoto, A. Shimizu, Z. Liu, D. M. Winker, Adjoint inversion modeling of Asian dust emission using lidar observations, Atmospheric Chemistry and Physics, 8, 11, 2869-2884, 2008.06, A four-dimensional variational (4D-Var) data assimilation system for a regional dust model (RAMS/CFORS-4DVAR; RC4) is applied to an adjoint inversion of a heavy dust event over eastern Asia during 20 March–4 April 2007. The vertical profiles of the dust extinction coefficients derived from NIES Lidar network are directly assimilated, with validation using observation data. Two experiments assess impacts of observation site selection: Experiment A uses five Japanese observation sites located downwind of dust source regions; Experiment B uses these and two other sites near source regions. Assimilation improves the modeled dust extinction coefficients. Experiment A and Experiment B assimilation results are mutually consistent, indicating that observations of Experiment A distributed over Japan can provide comprehensive information related to dust emission inversion. Time series data of dust AOT calculated using modeled and Lidar dust extinction coefficients improve the model results. At Seoul, Matsue, and Toyama, assimilation reduces the root mean square differences of dust AOT by 35–40%. However, at Beijing and Tsukuba, the RMS differences degrade because of fewer observations during the heavy dust event. Vertical profiles of the dust layer observed by CALIPSO are compared with assimilation results. The dense dust layer was trapped at potential temperatures () of 280–300 K and was higher toward the north; the model reproduces those characteristics well. Latitudinal distributions of modeled dust AOT along the CALIPSO orbit paths agree well with those of CALIPSO dust AOT, OMI AI, and MODIS coarse-mode AOT, capturing the latitude at which AOTs and AI have high values. Assimilation results show increased dust emissions over the Gobi Desert and Mongolia; especially for 29–30 March, emission flux is about 10 times greater. Strong dust uplift fluxes over the Gobi Desert and Mongolia cause the heavy dust event. Total optimized dust emissions are 57.9 Tg (Experiment A; 57.8% larger than before assimilation) and 56.3 Tg (Experiment B; 53.4% larger)..
46. Keiya Yumimoto, Itsushi Uno, Nobuo Sugimoto, Atsushi Shimizu, Modis aot based inverse modeling for Asian dust, Scientific Online Letters on the Atmosphere, 10.2151/sola.2008-023, 4, 1, 89-92, 2008.04, Inverse modeling of Asian dust was performed using MODIS coarse-mode aerosol optical thickness (AOT) and a regional adjoint dust model. The a posteriori AOT shows better agreement with the MODIS AOT and OMI Aerosol index (AI). Independent validation with the NIES Lidar network shows that the inversion leads to a significant improvement and reduces root mean squares of differences by 29-32% at Seoul, Matsue, and Toyama. The inversion results show considerably greater dust emissions over the Gobi Desert and Mongolia. Especially, optimized emissions are estimated as 8.1 Tg (352% of the a priori) for 29 March and 19.5 Tg (325%) for 30 March. Comparison with inversion results using NIES Lidar (Yumimoto et al. 2008) shows consistency with our a posteriori dust emissions which underscores the feasibility of dust inversion with satellite optical observations, and encourages combined inversion that assimilates the Lidar extinction coefficient (vertical profiles) and MODIS AOT (horizontal distribution) concurrently. However, the a posteriori results might reflect effects of air pollutants from highly industrialized regions, which might contaminate the assimilated results. Further quality control of the input for the data assimilation is necessary in future studies..
47. Itsushi Uno, Keiya Yumimoto, A. Shimizu, Yukari Hara, N. Sugimoto, Z. Wang, Z. Liu, D. M. Winker, 3D structure of Asian dust transport revealed by CALIPSO lidar and a 4DVAR dust model, Geophysical Research Letters, 10.1029/2007GL032329, 35, 6, 2008.03, We present detailed 3D structure of Asian dust outflow from a dust source region to the northwestern Pacific ocean retrieved by NASA/CALIOP onboard CALIPSO and results simulated by a four-dimensional variational (4DVAR) data assimilation version of a dust transport model (RC4) based on the NIES Lidar network. The modeled and CALIOP dust extinction showed good agreement, both for horizontal scale (600-1200 km) and vertical depth (1600-3600 m) near the dust source regions. Cross-section analyses of CALIOP and RC4 assisted by forward trajectory revealed that dust from the Gobi Desert on 5 May traveled approximately 1000-1500 km/day to the east and passed over Japan on 8 May. The elevated dust subsequently passed to the Pacific Ocean while maintaining the major dust layer height of 2500-4000 m MSL trapped within the potential temperature of 302-306 K. Results of our analyses demonstrate the importance of integration of CALIOP measurement and the dust model for clarifying the overall structure of an Asian dust event..
48. Nobuo Sugimoto, Ichiro Matsui, Atsushi Shimizu, Tomoaki Nishizawa, Yukari Hara, Chenbo Xie, Itsushi Uno, Keiya Yumimoto, Zifa Wang, Soon Chang Yoon, Lidar network observations of tropospheric aerosols, Lidar Remote Sensing for Environmental Monitoring IX Lidar Remote Sensing for Environmental Monitoring IX, 10.1117/12.806540, 7153, 2008, Observations of tropospheric aerosols (mineral dust, air-pollution aerosols, etc.) and clouds are being conducted using a network of two-wavelength (1064nm, 532nm) polarization (532nm) lidars in the East Asian region. Currently, the lidars are operated continuously at 23 locations in Japan, Korea, China, Mongolia and Thailand. A real-time data processing system was developed for the network, and the data products such as the attenuated backscatter coefficients and the estimated extinction coefficients for non-spherical and spherical aerosols are generated automatically for online network stations. The data are used in the real-time monitoring of Asian dust as well as in the studies of regional air pollution and climate change..
49. Keiya Yumimoto, Itsushi Uno, N. Sugimoto, A. Shimizu, S. Satake, Adjoint inverse modeling of dust emission and transport over East Asia, Geophysical Research Letters, 10.1029/2006GL028551, 34, 8, 2007.04, A four-dimensional variational (4DVAR) data assimilation system was developed for a regional dust model. This report presents results of the first adjoint inversion of Asian dust emissions over East Asia using NIES LIDAR observations, targeting the extreme dust phenomenon on 30 April 2005. Optimized dust emissions mitigated underestimation of dust concentrations and brought the structure of the elevated dust layer (both onset timing and extinction coefficient intensity) into better agreement with LIDAR observations. We obtained a 31% (3.2 Tg) increase of calculated dust emissions through data assimilation, especially over the Mongolian region. The assimilated results agree with the TOMS AI distribution and indicate that the 4DVAR method is very powerful for unification of observation and numerical modeling. The method provides better estimation capability..
50. Keiya Yumimoto, Itsushi Uno, Chapter 3.6 Application of four-dimensional variational (4DVAR) data assimilation for optimal estimation of mineral dust and CO emissions in eastern Asia, Air Pollution Modeling and Its Application XVIII, 10.1016/S1474-8177(07)06036-6, 6, 318-328, 2007, A four-dimensional variational (4DVAR) data assimilation system was developed for a regional chemical transport model (CTM). In this study, we applied it to inverse modeling of CO emissions and mineral dust emission flux over East Asia, and demonstrated the feasibility of our assimilation system. In CO inverse modeling, three ground-based observations were used for estimating CO emission over East Asia. Assimilated results showed better agreement with observations; the RMS differences were reduced by 16-27%. CO emission over industrialized east central China between Shanghai and Beijing has increased markedly, and the results show that the annual anthropogenic (fossil and biofuel combustion) CO emission over China are 147 Tg. In dust inverse modeling, NIES LIDAR observations were used. The assimilated results better reflects the presence of the elevated dust layer and improved the under-prediction of dust concentrations. We obtained an 18% increase in calculated dust emissions through data assimilations, especially over the Mongolian region, indicating that the observed high-dense dust layer might originate in that region. These data assimilation results indicate that the 4DVAR method is very powerful for unification of observation and numerical modeling by CTM..
51. Keiya Yumimoto, Itsushi Uno, Adjoint inverse modeling of CO emissions over Eastern Asia using four-dimensional variational data assimilation, Atmospheric Environment, 10.1016/j.atmosenv.2006.05.042, 40, 35, 6836-6845, 2006.11, We developed a four-dimensional variational (4DVAR) data assimilation system for a regional chemical transport model (CTM). In this study, we applied it to inverse modeling of CO emissions in the eastern Asia during April 2001 and demonstrated the feasibility of our assimilation system. Three ground-based observations were used for data assimilation. Assimilated results showed better agreement with observations; they reduced the RMS difference by 16-27%. Observations obtained on board the R/V Ronald H. Brown were used for independent validation of the assimilated results. The CO emissions over industrialized east central China between Shanghai and Beijing were increased markedly by the assimilation. The results show that the annual anthropogenic (fossil and biofuel combustion) CO emissions over China are 147 Tg. Sensitivity analyses using the adjoint model indicate that the high CO concentration measured on 17 April at Rishiri, Japan (which the assimilation was unable to reproduce) originated in Russia or had traveled from outside the Asian region (e.g. Europe)..