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Hidaka, Akihide; Kawashima, Shigeto*; Kajino, Mizuo*
Journal of Nuclear Science and Technology, 60(7), p.743 - 758, 2023/07
Times Cited Count：2 Percentile：90.12(Nuclear Science & Technology)An accurate estimation of radionuclides released during the Fukushima accident is essential. Therefore, authors investigated Te release using the Unit emission-regression estimation method, in which the deposition distribution is weighted based on the hourly deposition obtained from mesoscale meteorological model calculations assuming Unit emissions. The previous study focused on confirming the applicability of this method. Subsequent examination revealed that if any part of the time when a release have occurred is missing from the estimated release period, the entire source term calculation will be distorted. Therefore, this study performed the recalculation by extending the estimation period to cover all major releases. Consequently, unspecified release events were clarified, and their correspondence to in-core events was confirmed. The 
Te release caused by Zr cladding complete oxidation can explain the regional dependence of the Te/
Cs ratio in the soil contamination map.
Kajino, Mizuo*; Adachi, Koji*; Igarashi, Yasuhito*; Satou, Yukihiko; Sawada, Morihiro*; Sekiyama, Tsuyoshi*; Zaizen, Yuji*; Saya, Akane*; Tsuruta, Haruo*; Moriguchi, Yuichi*
Journal of Geophysical Research; Atmospheres, 126(1), p.e2020JD033460_1 - e2020JD033460_23, 2021/01
Times Cited Count：12 Percentile：72.21(Meteorology & Atmospheric Sciences)Kubota, Tomohiro; Kuroda, Hisao*; Watanabe, Mirai*; Takahashi, Akiko*; Nakazato, Ryoji*; Tarui, Mika*; Matsumoto, Shunichi*; Nakagawa, Keita*; Numata, Yasuko*; Ouchi, Takao*; et al.
Atmospheric Environment, 243, p.117856_1 - 117856_9, 2020/12
Times Cited Count：3 Percentile：15.82(Environmental Sciences)The dry and wet depositions of atmospheric ammonia (NH
) is one of the important pathways of nitrogen loads to aquatic ecosystems. Crop and livestock agriculture, one of the largest emitters of NH in Asian countries, are known to cause high spatial and seasonal variation of NH and influence the surrounding lake basin areas via its dry and wet deposition. However, the spatial characteristics of the NH concentration in basin scale are not completely understood for regulation in NH emission. Here we aim to clarify dominant factors of spatial and seasonal variations of the NH concentration in a eutrophic lake basin surrounded by agricultural areas in Japan. Passive sampling over various land use categories in the basin was conducted at 36 sites in total from October 2018 to January 2020. Interestingly, the observed NH concentration near the livestock houses were higher in winter than summer, which was inconsistent with knowledge of seasonal changes of current NH emission inventory based on temperature-driven volatilization process. Comparing monthly NH concentrations with various meteorological factors, we suggested the importance of seasonal advection of NH from high emission sources to which has been rarely paid attention by the previous past studies. As for this, should be considered for lake ecosystem management since deposition of NH is known to be closely related to the ecological processes such as phytoplankton blooming.
Cs concentrations from the Fukushima Daiichi Nuclear Power Plant accident, phase III; Simulation with an identical source term and meteorological field at 1-km resolutionSato, Yosuke*; Sekiyama, Tsuyoshi*; Fang, S.*; Kajino, Mizuo*; Qu
rel, A.*; Qulo, D.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.
Atmospheric Environment; X (Internet), 7, p.100086_1 - 100086_12, 2020/10
The third model intercomparison project for investigating the atmospheric behavior of Cs emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident (FDNPP-MIP) was conducted. A finer horizontal grid spacing (1 km) was used than in the previous FDNPP-MIP. Nine of the models used in the previous FDNPP-MIP were also used, and all models used identical source terms and meteorological fields. Our analyses indicated that most of the observed high atmospheric Cs concentrations were well simulated, and the good performance of some models improved the performance of the multi-model ensemble. The analyses also confirmed that the use of a finer grid resolution resulted in the meteorological field near FDNPP being better reproduced. The good representation of the wind field resulted in the reasonable simulation of the narrow distribution of high deposition amount to the northwest of FDNPP and the reduction of the overestimation over the area to the south of FDNPP. In contrast, the performance of the models in simulating plumes observed over the Nakadori area, the northern part of Gunma, and the Tokyo metropolitan area was slightly worse.
Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input dataSato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qulo, D.*; et al.
Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10
Times Cited Count：40 Percentile：85.28(Meteorology & Atmospheric Sciences)A model intercomparison of the atmospheric dispersion of Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed Cs events, and the figure-of-merit in space for the total deposition of Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the Cs concentrations.
Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of JapanKitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.
Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07
Times Cited Count：24 Percentile：69.81(Meteorology & Atmospheric Sciences)We compared seven atmospheric transport model results for Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.
Katata, Genki; Chino, Masamichi; Kobayashi, Takuya; Terada, Hiroaki; Ota, Masakazu; Nagai, Haruyasu; Kajino, Mizuo*; Draxler, R.*; Hort, M.*; Malo, A.*; et al.
Atmospheric Chemistry and Physics, 15(2), p.1029 - 1070, 2015/01
Times Cited Count：220 Percentile：98.87(Environmental Sciences)We estimated a detailed time trend of atmospheric releases during the Fukushima Dai-ichi Power Station (FNPS1) accident by combining environmental monitoring data with coupling simulation of atmospheric model of WSPEEDI-II, and oceanic dispersion model of SEA-GEARN-FDM. The new scheme of dry and fogwater depositions, in-cloud scavenging, cloud condensation nuclei activity, and wet scavenging by ice phase for radioactive iodine gas and other particles was incorporated into WSPEEDI-II. The results revealed that the major releases of radionuclides occurred in the following periods: afternoon on 12 March when the wet venting and hydrogen explosion at Unit 1, morning on 13 March after the venting event at Unit 3, midnight on 14 March when three-time openings of SRV were conducted at Unit 2, morning and night on 15 March, and morning on 16 March.
Katata, Genki; Kajino, Mizuo*; Matsuda, Kazuhide*; Takahashi, Akira*; Nakaya, Ko*
Atmospheric Environment, 97, p.501 - 510, 2014/11
Times Cited Count：13 Percentile：36.77(Environmental Sciences)To investigate the impact of hygroscopic growth on dry deposition onto forest canopies, numerical simulations of PM2.5 sulfate deposition using a multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) ware performed. The scheme of particle dry deposition in SOLVEG was extended for application to a broad-leaved forest. An aerosol hygroscopic model based on the widely used 
-K
hler theory was incorporated into the model to calculate water uptake by the aerosols. The model accurately reproduced essential turbulent exchange fluxes (momentum, heat, and water vapor) over the canopies and the soil temperature and moisture for a deciduous broad-leaved forest in central Japan. Temporal variations in the measured PM2.5 sulfate deposition velocity were generally reproduced by the model. By considering an increase in particle diameter due to hygroscopic growth, the prediction accuracy of the modeled deposition velocity under humid conditions was improved. Numerical experiments for varying aerosol size distributions and hygroscopic properties showed that the geometric mean diameter and hygroscopicity of particles have a large influence on hygroscopic growth levels. The results also suggested that the deposition velocity of wet particles increased due to hygroscopic growth when the relative humidity (RH) was approximately 50%, and that the velocity reached five times greater than that under dry conditions when RH exceeded 95%.
Kajino, Mizuo*; Inomata, Yayoi*; Sato, Keiichi*; Ueda, Hiromasa*; Han, Z.*; An, J.*; Katata, Genki; Deushi, Makoto*; Maki, Takashi*; Oshima, Naga*; et al.
Atmospheric Chemistry and Physics, 12(24), p.11833 - 11856, 2012/12
Times Cited Count：45 Percentile：74.69(Environmental Sciences)A new aerosol chemical transport model, Regional Air Quality Model 2 (RAQM2), was developed to simulate Asian air quality. We implemented a simple version of a modal-moment aerosol dynamics model and achieved completely dynamic solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super micro m. To consider a variety of atmospheric aerosol properties, a category approach is utilized: aerosols are distributed into 4 categories, Aitken, accumulation, soot aggregates, and coarse mode. A regional-scale simulation was performed for the entire year of 2006, covering Northeast Asian region. Statistical analysis showed the model reproduced the regional-scale transport and transformation of the major inorganic anthropogenic and natural air constituents within factors of 2 to 5. Modeled size distributions of total weight and chemical components were consistent with the observations, indicating simulations of aerosol mixing types were successful.
Katata, Genki; Kajino, Mizuo*; Hiraki, Takatoshi*; Aikawa, Masahide*; Kobayashi, Tomiki*; Nagai, Haruyasu
Journal of Geophysical Research, 116(D20), p.D20102_1 - D20102_14, 2011/10
Times Cited Count：29 Percentile：59.27(Meteorology & Atmospheric Sciences)To apply the meteorological model to investigate fog occurrence, acidification, and deposition in mountain forests, the meteorological model WRF was modified to calculate the fog deposition by the simple linear function of fog deposition onto vegetation. The modified version of WRF that includes fog deposition (fog-WRF) was tested in a mountain forest of Mt. Rokko in Japan. The fog-WRF provided a clearly better prediction of liquid water content of fog (LWC) than the original version of WRF. The fog-WRF successfully simulated measured throughfall observations due to fog deposition inside the forest. Using the linear relationship between fog deposition and the altitude given by the fog-WRF calculations and the data from throughfall observations at the certain altitude, vertical distribution of fog deposition can be roughly estimated in mountain forest. The meteorological model that includes the fog deposition is useful for mapping the fog deposition in mountain cloud forests.
Katata, Genki; Nagai, Haruyasu; Kajino, Mizuo*; Ueda, Hiromasa*; Hozumi, Yu*
Agricultural and Forest Meteorology, 150(3), p.340 - 353, 2010/03
Times Cited Count：31 Percentile：76.95(Agronomy)The aim of the present study is to evaluate fog deposition on vegetation and its contribution to water and energy balance in arid regions using a detailed land surface model including fog deposition on vegetation under meteorological conditions simulated by a meteorological model. The results of estimated fog deposition indicated that fog deposition provided a more effective water source for plant growth as compared to heavy rainfall in arid areas. Evaporation from leaf surface water eases the plant's water stress via reducing transpiration. Latent heat of evaporation from the leaf surface water and soil causes temperature reduction of soil and leaves during the daytime. Moreover, decreased transpiration rates as a result of increased evaporation from the leaf surface water due to fog deposition, yields an effective water source to be used for photosynthesis for those plants suffering from severe water stress in arid environments.
Katata, Genki; Nagai, Haruyasu; Kajino, Mizuo*; Ueda, Hiromasa*
no journal, ,
no abstracts in English
Kajino, Mizuo*; Katata, Genki; Nagai, Haruyasu; Ishikawa, Hirohiko*; Ueda, Hiromasa*
no journal, ,
no abstracts in English
Katata, Genki; Kajino, Mizuo*; Hiraki, Takatoshi*; Aikawa, Masahide*; Kobayashi, Tomiki*
no journal, ,
Water and matter deposition via fog precipitation onto the ceder trees was investigated using the models of three-dimensional mesoscale model (WRF), aerosol transport model (EMTACS), and land surface model including fog deposition on vegetation (SOLVEG). Simulations using WRF, EMTACS, and SOLVEG were independently carried out to produce meteorological variables, chemical compositions, and fog precipitation, respectively. Meteorological variables were overall reproduced by WRF. Fog precipitation estimation by SOLVEG using the output from WRF significantly underestimated throughfall measurements. It was considerable that "edge effect' enhanced fog precipitation in measurements in addition to fog deposition by turbulent vertical mixing of fog water. EMTACS resolved temporal evolutions in chemical compositions in fog water and size distribution of aerosols. WRF-SOLVEG-EMTACS system should be improved in future to assess matter deposition via fog precipitation.
Katata, Genki; Kajino, Mizuo*; Hiraki, Takatoshi*; Aikawa, Masahide*; Kobayashi, Tomiki*; Nagai, Haruyasu
no journal, ,
Water and matter input via fog deposition onto a mountainous forest (Mt. Rokko, Japan) was investigated using detailed land surface model that includes fog deposition onto vegetation (SOLVEG). Simulations using SOLVEG were carried out under meteorological and chemical fields produced by off-line coupled meso-scale meteorological/aerosol chemical transport model (WRF/EMTACS). The SOLVEG clearly underestimated the cumulative fog deposition calculated from throughfall data. This suggests that an enhancement of fog deposition by "edge effect" which is the phenomenon that fog droplets carried by horizontal advection are captured by leaves under canopy clustering and inhomogeneity. The deposition of atmospheric pollutants onto the forest floor due to fog deposition was estimated from the fog deposition by SOLVEG and chemical concentrations in fog water predicted by WRF/EMTACS.
Kajino, Mizuo*; Katata, Genki; Hiraki, Takatoshi*; Aikawa, Masahide*; Kobayashi, Tomiki*
no journal, ,
In order to predict water and matter deposition to forests, accurate estimation of chemical and physical properties of fog and aerosols are indispensable. We have developed a new aerosol chemical transport model (EMTACS) coupled with a meteorological model (WRF) and applied it to investigate uplift fog events occurred over a mountainous forest (Mt. Rokko, Japan). The EMTACS model is unique to dynamically solve temporal evolutions of mixing states of fog and aerosols, in addition to their chemical compositions and size distributions, and thus aerosol-fog interaction processes are considered in one coherent framework. The model performance was evaluated using meteorological and chemical observation data. Formation, evolution and acidification processes of fog and aerosols over the forest region were discussed.
Katata, Genki; Kajino, Mizuo*; Hiraki, Takatoshi*; Aikawa, Masahide*; Kobayashi, Tomiki*; Nagai, Haruyasu
no journal, ,
no abstracts in English
Kajino, Mizuo*; Deushi, Makoto*; Maki, Takashi*; Aoyagi, Toshinari*; Igarashi, Yasuhito*; Mikami, Masao*; Inomata, Yayoi*; Katata, Genki
no journal, ,
no abstracts in English
Katata, Genki; Kajino, Mizuo*; Nagai, Haruyasu
no journal, ,
A sophisticated multi-layer land surface model (SOLVEG) was applied to mountain forest in Japan to test its performance in predicting the aerosol deposition on vegetation in East Asia. The model calculates the dry deposition of gases and size-resolved particles at each canopy layer. Using the output data from meteorological and chemical transport models, the calculations of deposition velocities of the SO
and NH and size-resolved aerosols by SOLVEG was carried out. The SOLVEG reproduced a typically observed diurnal pattern in dry deposition velocities of SO and NH as those increased during the daytime due to the stomata uptake. The calculated size-resolved deposition velocity of aerosols agreed with the observed data obtained from the throughfall measurements in the study site.
Kajino, Mizuo*; Katata, Genki; Hiraki, Takatoshi*; Aikawa, Masahide*; Kobayashi, Tomiki*; Ueda, Hiromasa*
no journal, ,
We numerically evaluated depositional pathways of major air pollutants such as SO
, NH
, NO
, Cl
, and Na
over mountain forest areas in Mt. Rokko in July 1999. A modified WRF model including fog deposition (fog-WRF) and Regional Air Quality Model 2 (RAQM2) was used for simulations. To show the consistency of the model performance, the measured chemical components in fog water were compared with the modeled concentrations. During the simulation period, the persistent southerly wind carried humid air from the Osaka Bay to Mt. Rokko and caused condensation along mountain ridges higher than 400 m in altitude during nights. Simulation results showed that fog deposition was dominant for all depositional components, while dry deposition of nitrate was large due to the high deposition velocity of HNO gas.
