Faculty Profiles - KURITA Naoyuki

Papers - KURITA Naoyuki

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Characteristics of tritium, stable isotopes and chemical components in monthly precipitation at Hiroshima, Japan.

Yamada R, Kuwata H, Kheamsiri K, Ohno K, Kitayama Y, Yoshinaka Y, Yoshinaga S, Kurita N, Akata N

Radiation protection dosimetry Vol. 200 ( 16-18 ) page： 1797 - 1801 2024.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Radiation Protection Dosimetry

This article mainly discusses tritium concentrations in monthly precipitation at Hiroshima City during 2021. The tritium concentrations, which were measured with a low background liquid scintillation counter, fluctuated from 0.16 to 0.78 Bq L−1. Additionally, hydrogen and oxygen stable isotopes and ionic species were measured in order to characterize precipitation, and their trends including tritium concentrations were compared with data collected in other regions of Japan in previous studies. Although the results showed the characteristics of precipitation were similar to those observed in the other regions, the tritium concentrations were found to be contrary to behavior expected from the latitude effect and some of the observed ionic components were suggested to be continental in origin. Since these results are not common at other sites in Japan, the tritium concentration in the westernmost region of Honshu, including Hiroshima City, may be influenced by Asian continental influences.

DOI： 10.1093/rpd/ncae024

Scopus

PubMed

Near-Surface Air Temperature Records over the Past 30 Years in the Interior of Dronning Maud Land, East Antarctica

Kurita N., Kameda T., Motoyama H., Hirasawa N., Mikolajczyk D., Welhouse L.J., Keller L.M., Weidner G.A., Lazzara M.A.

Journal of Atmospheric and Oceanic Technology Vol. 41 ( 2 ) page： 179 - 188 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Atmospheric and Oceanic Technology

The interior of Dronning Maud Land (DML) in East Antarctica is one of the most data-sparse regions of Antarctica for studying climate change. A monthly mean near-surface temperature dataset for the last 30 years has been compiled from the historical records from automatic weather stations (AWSs) at three sites in the region (Mizuho, Relay Station, and Dome Fuji). Multiple AWSs have been installed along the route to Dome Fuji since the 1990s, and observations have continued to the present day. The use of passive-ventilated radiation shields for the temperature sensors at the AWSs may have caused a warm bias in the temperature measurements, however, due to insufficient ventilation in the summer, when solar radiation is high and winds are low. In this study, these warm biases are quantified by comparison with temperature measurements with an aspirated shield and subsequently removed using a regression model. Systematic error resulting from changes in the sensor height due to accumulating snow was insignificant in our study area. Several other systematic errors occurring in the early days of the AWS systems were identified and corrected. After the corrections, multiple AWS records were integrated to create a time series for each station. The percentage of missing data over the three decades was 21% for Relay Station and 28% for Dome Fuji. The missing rate at Mizuho was 49%, more than double that at Relay Station. These new records allow for the study of temperature variability and change in DML, where climate change has so far been largely unexplored. SIGNIFICANCE STATEMENT: Antarctic climate change has been studied using temperature data at staffed stations. The staffed stations, however, are mainly located on the Antarctic Peninsula and in the coastal regions. Climate change is largely unknown in the Antarctic plateau, particularly in the western sector of the East Antarctic Plateau in areas such as the interior of Dronning Maud Land (DML). To fill the data gap, this study presents a new dataset of monthly mean near-surface climate data using historical observations from three automatic weather stations (AWSs). This dataset allows us to study temperature variability and change over a data-sparse region where climate change has been largely unexplored.

DOI： 10.1175/JTECH-D-23-0092.1

Scopus

Regional variations in mineralogy of dust in ice cores obtained from northeastern and northwestern Greenland over the past 100 years

Naoko Nagatsuka, Kumiko Goto-Azuma, Koji Fujita, Yuki Komuro, Motohiro Hirabayashi, Jun Ogata, Kaori Fukuda, Yoshimi Ogawa-Tsukagawa, Kyotaro Kitamura, Ayaka Yonekura, Fumio Nakazawa, Yukihiko Onuma, Naoyuki Kurita, Sune Olander Rasmussen, Giulia Sinnl, Trevor James Popp, Dorthe Dahl-Jensen

2023.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. To investigate regional and temporal variations in the sources and atmospheric transport processes for mineral dust deposited on the Greenland Ice Sheet, we analysed the morphology and mineral composition of dust in an ice core from northeastern Greenland (East Greenland Ice-Core Project, EGRIP), representing the period from 1910 to 2013, using scanning electron microscopy and energy-dispersive X-ray spectroscopy, and compared the results with those previously obtained for an ice core from northwestern Greenland (SIGMA-D). The composition of the SIGMA-D ice-core dust, comprising mostly silicate minerals, varied on a multi-decadal timescale due to an increased contribution of minerals originating from local ice-free areas during recent warming periods. In contrast, for the EGRIP ice-core dust, also consisting mostly of silicate minerals, there was relatively low compositional variation among the samples, suggesting that the mineral sources have not changed dramatically over the past 100 years. The subtle variation in the EGRIP ice-core mineral composition is likely due to a minor contribution of local dust. The type of silicate minerals differed significantly between the two ice cores; micas and chlorite, which form in cold dry regions, were abundant in the EGRIP ice core, whereas kaolinite, which forms in warm humid regions, was abundant in the SIGMA-D ice core. This indicates that the EGRIP ice-core dust likely originated from different geological sources than those for the SIGMA-D dust. A back-trajectory analysis indicated that the ice-core dust was transported from Northern Eurasia and North America to the EGRIP site, and that the contribution from each source was likely smaller and larger, respectively, than those for the SIGMA-D ice core. Furthermore, the higher illite content in the EGRIP ice core suggests dust transportation from Asian deserts. Although the back-trajectory analysis suggests that most of the air mass that arrived at the EGRIP site came from the Greenland coast, the mineral grain size and composition results showed that the local dust contribution was likely small.

DOI： 10.5194/egusphere-2023-1666

Verification of Estimated Cosmic Neutron Intensities Using a Portable Neutron Monitoring System in Antarctica

Yasuda H., Kurita N., Yajima K.

Applied Sciences (Switzerland) Vol. 13 ( 5 ) 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Sciences (Switzerland)

Featured Application: A portable neutron-monitoring system can be effectively applied to verification of the models used for estimating cosmic radiation intensities over a wide range of altitudes in a harsh environment such as in Antarctica. Many ongoing studies for predicting the production rates of cosmogenic nuclides, forecasting changes of atmospheric compositions and climate, assessing the cosmic-radiation exposure of aircraft crew, and the effects on precise electronic devices use numerical models that estimate cosmic-radiation intensities in the atmosphere. Periodic verifications of those models are desirable to be performed for assuring the reliability of the study outcomes. Here, we investigated an application of a portable neutron-monitoring system composed of an extended-energy-range neutron monitor and a small data logger for monitoring of cosmic-neutron intensities in a polar region. As a result of measurements in the east Antarctica region covering a wide range of altitudes (from 30 m to 3762 m) and comparisons with the model calculations performed with an analytical model based on comprehensive Monte Carlo simulations (PARMA), it was demonstrated that the portable neutron-monitoring system could be effectively applied for periodic verification of cosmic-neutron intensities that would improve the reliability of related studies.

DOI： 10.3390/app13053297

Scopus

Temporal variations of surface mass balance over the last 5000 years around Dome Fuji, Dronning Maud Land, East Antarctica

Oyabu I., Kawamura K., Fujita S., Inoue R., Motoyama H., Fukui K., Hirabayashi M., Hoshina Y., Kurita N., Nakazawa F., Ohno H., Sugiura K., Suzuki T., Tsutaki S., Abe-Ouchi A., Niwano M., Parrenin F., Saito F., Yoshimori M.

Climate of the Past Vol. 19 ( 2 ) page： 293 - 321 2023.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Climate of the Past

We reconstructed surface mass balance (SMB) around Dome Fuji, Antarctica, over the last 5000 years using the data from 15 shallow ice cores and seven snow pits. The depth-age relationships for the ice cores were determined by synchronizing them with a layer-counted ice core from West Antarctica (WAIS Divide ice core) using volcanic signals. The reconstructed SMB records for the last 4000 years show spatial patterns that may be affected by their locations relative to the ice divides around Dome Fuji, proximity to the ocean, and wind direction. The SMB records from the individual ice cores and snow pits were stacked to reconstruct the SMB history in the Dome Fuji area. The stacked record exhibits a long-term decreasing trend at -0.037±0.005g€¯kgg€¯m-2 per century over the last 5000 years in the preindustrial period. The decreasing trend may be the result of long-term surface cooling over East Antarctica and the Southern Ocean and sea ice expansion in the water vapor source areas. The multidecadal to centennial variations of the Dome Fuji SMB after detrending the record shows four distinct periods during the last millennium: a mostly negative period before 1300g€¯CE, a slightly positive period from 1300 to 1450g€¯CE, a slightly negative period from 1450 to 1850g€¯CE with a weak maximum around 1600g€¯CE, and a strong increase after 1850g€¯CE. These variations are consistent with those of previously reconstructed SMB records in the East Antarctic plateau. The low accumulation rate periods tend to coincide with the combination of strong volcanic forcings and solar minima for the last 1000 years, but the correspondence is not clear for the older periods, possibly because of the lack of coincidence of volcanic and solar forcings or the deterioration of the SMB record due to a smaller number of stacked cores.

DOI： 10.5194/cp-19-293-2023

Scopus

Seasonal changes in stable isotope ratio of water and tritium concentration of the Lena River discharge in eastern Siberia: Possibility of end-member mixing analysis to differentiate river water into several sources

Hiyama Tetsuya, Homma Asaka, Kurita Naoyuki, Asai Kazuyoshi, Park Hotaek

Proceeding of Annual Conference Vol. 36 ( 0 ) page： 340 2023

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES

<p>The water cycle in northern Eurasia is drastically changing due to climate warming and Arctic sea ice retreat. To better understand the changing water cycle including permafrost thaw and groundwater discharge into sub-Arctic rivers, seasonal changes in stable water isotopes and tritium concentrations were obtained from April 2020 to March 2021 at the Tabaga hydrological station in the middle of the Lena River basin. Stable water isotopes and tritium concentration showed distinct seasonal variations relating with the water level. Interestingly, hysteresis was found between the stable isotope ratios and tritium concentrations. This implies contributions of groundwater (ground ice-melt water) and snow-melt water to the Lena River discharge differ with clear seasonality. Plotting end-member values of ground ice, groundwater, snow, and summer rain water showed that EMMA (end-member mixing analysis) could be applicable for detecting seasonal change of source waters to the Lena River discharge.</p>

DOI： 10.11520/jshwr.36.0_340

CiNii Research

Spatial variations of <sup>10</sup>Be in surface snow along the inland traverse route of Japanese Antarctic Research Expeditions

Horiuchi K., Kato S., Ohtani K., Kurita N., Tsutaki S., Nakazawa F., Motoyama H., Kawamura K., Tazoe H., Akata N., Yamagata T., Matsuzaki H.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms Vol. 533 page： 61 - 65 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

To contribute further to understanding of the nature of 10Be deposition in Antarctica, we determined 10Be concentrations in surface snow samples obtained along the inland traverse route of the 59th and 60th Japanese Antarctic Research Expeditions (JAREs) in eastern Dronning Maud Land. The 10Be concentrations ranged between 3.7 × 103 and 8.6 × 104 atoms/g. When plotted against latitude, they showed a clear trend of increasing concentration southward with an upward inflection point at around 75°S (elevation 3.5 km) for the 59th JARE. Comparison with both snow accumulation rate and δ18O data suggests that the inflection point divides the dominant deposition regime into two different groups: wet deposition (north of 75°S) and dry deposition with slight enhancement of 10Be fallout further inland (south of 75°S). Additional factors associated with 10Be transport from the stratosphere are also proposed.

DOI： 10.1016/j.nimb.2022.10.018

Scopus

Monthly Precipitation Collected at Hirosaki, Japan: Its Tritium Concentration and Chemical and Stable Isotope Compositions

Kuwata H., Akata N., Okada K., Tanaka M., Tazoe H., Kurita N., Otashiro N., Negami R., Suzuki T., Tamakuma Y., Shiroma Y., Hosoda M.

Atmosphere Vol. 13 ( 5 ) 2022.5

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Atmosphere

Monthly precipitation samples were collected at Hirosaki, Aomori Prefecture from January 2018 to December 2020 to measure the ion species and stable hydrogen and oxygen isotope ratios in order to understand the regional properties. The tritium concentration ranged from 0.28 to 1.20 Bq/L, with mean values (±S.D.) of 0.52 ± 0.18, 0.67 ± 0.25 and 0.63 ± 0.21 Bq/L in 2018, 2019 and 2020, respectively. This concentration level was almost the same as for Rokkasho, Aomori Prefecture. The tritium concentration had clear seasonal variation: high in the spring and low in the summer. This trend was thought to arise from seasonal fluctuations in the atmospheric circulation. On the other hand, the pH tended to be low, and the electrical conductivity (EC) tended to be high from the winter to the spring. The ion components, which major ion species contained in sea salt, also tended to be high in the winter, and these components had a strong influence on EC. The d-excess values were high in the winter and low in the summer, and when this trend was considered from the viewpoint of the wind direction data in Hirosaki, these dust components were attributed to the northwest monsoon in the winter to the spring coming from the Asian continent.

DOI： 10.3390/atmos13050848

Scopus

Comparison of Ventilated and Unventilated Air Temperature Measurements in Inland Dronning Maud Land on the East Antarctic Plateau

Morino S., Kurita N., Hirasawa N., Motoyama H., Sugiura K., Lazzara M., Mikolajczyk D., Welhouse L., Keller L., Weidner G.

Journal of Atmospheric and Oceanic Technology Vol. 38 ( 12 ) page： 2061 - 2070 2021.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Atmospheric and Oceanic Technology

Surface temperature measurements with naturally ventilated (NV) sensors over the Antarctic Plateau are largely subject to systematic errors caused by solar radiative heating. Here we examined the radiative heating error in Dronning Maud Land on the East Antarctic Plateau using both the newly installed automatic weather stations (AWSs) at NDF and Relay Station and the existing AWSs at Relay Station and Dome Fuji. Two types of NV shields were used in these AWSs: a multiplate radiation shield and a simple cylinder-shaped shield. In austral summer, the temperature bias between the force-ventilated (FV) sensor and the NV sensor never reached zero because of continuous sunlight. The hourly mean temperature errors reached up to 8°C at noon on a sunny day with weak wind conditions. The errors increased linearly with increasing reflected shortwave radiation and decreased nonlinearly with increasing wind speed. These features were observed in both the multiplate and the cylinder-shaped shields. The magnitude of the errors of the multiplate shield was much larger than that of the cylinder-shaped shield. To quantify the radiative errors, we applied an existing correction model based on the regression approach and successfully reduced the errors by more than 70% after the correction. This indicates that we can use the corrected temperature data instead of quality controlled data, which removed warm bias during weak winds in inland Dronning Maud Land.

DOI： 10.1175/JTECH-D-21-0107.1

Scopus

Isotope and chemical composition of monthly precipitation collected at Sapporo, northern part of Japan during 2015-2019

Fusion Engineering and Design Vol. 168 2021.7

Climate response of oxygen isotopic compositions in tree-ring cellulose in java: Evaluation using a proxy system model

Atmosphere Vol. 12 ( 3 ) 2021.3

Temporal variations in Antarctic ice sheet surface accumulation observed with snow depth sensors in automatic weather stations Reviewed

Naohiko Hirasawa, Hideaki Motoyama, Kyohei Yamada, Kounosuke Sugiura, Naoyuki Kurita

SEPPYO Vol. 83 ( 1 ) page： 67 - 77 2021.1

Temporal variations in Antarctic ice sheet surface accumulation observed withsnow depthsensors in automatic weather stations

HIRASAWA Naohiko, MOTOYAMA Hideaki, YAMADA Kyohei, SUGIURA Konosuke, KURITA Naoyuki

Journal of the Japanese Society of Snow and Ice Vol. 83 ( 1 ) page： 67 - 77 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Society of Snow and Ice

Automatic Weather Stations (AWSs) with ultrasonic snow depth sensors were newly installed at four sites. The installation was started in January 2016 and completed in October 2019. The sites are H128 in the coastal region, MD78 in the continental slope region with the katabatic wind, NRP in the inland high region on the upside of the continental slope, and NDF on the summit of the ice sheet. The purpose of this AWS system is to clarify the temporal variations of accumulations affected by synoptic-scale disturbances and diurnal variations while reflecting the regional characteristics over a wide area of the Antarctic ice sheet. This paper investigates the temporal variations of surface height observed at these four sites. The results are as follows: 1) The temporal changes of surface height include stepwise fluctuations and pulse-like fluctuations, and the rise in surface height is mainly caused by stepwise rises, rather than pulse-like fluctuations. 2) A comparison between H128 and NRP showed four cases in which surface height fluctuations appeared simultaneously over a wide area. The NOAA infrared image reveals that the cloud area associated with a synoptic-scale disturbance formed over the ice sheet. 3) The surface height is less likely to rise largely between different sites on the same day. 4) At the three sites other than NRP, a slow decline in surface height was observed during the warm season.

DOI： 10.5331/seppyo.83.1_67

Origin analysis of trace elements including arsenic in travertine springs in northwestern Iran

Kaneko Masaki, Asahara Yoshihiro, Minami Masayo, Kurita Naoyuki, Azizi Hossein, Amin―Rasouli Hadi, Zhang Yubo

Abstracts of Annual Meeting of the Geochemical Society of Japan Vol. 68 ( 0 ) page： 125 2021

Dating and solid particle analysis of a shallow ice core drilled at EGRIP, Greenland

Komuro Yuki, Nakazawa Fumio, Goto-Azuma Kumiko, Hirabayashi Motohiro, Ogata Jun, Fukuda kaori, Kurita Naoyuki, Kitamura Kyotaro, Yonekura Ayaka, Popp Trevor J., Dahl-Jensen Dorthe

Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research Vol. 2021 ( 0 ) page： 22 - 22 2021

Atmospheric factors controlling stable isotope variations in modern precipitation of the tropical region of Bangladesh.

Ahmed N, N. Kurita, Chowdhury MAM, Gao J, Hassan SMQ, Mannan MA, Mallik MAK, Choudhury SA, Bhuiyan MAQ, Karim MM

Isotopes in environmental and health studies Vol. 56 ( 3 ) page： 220-237 2020.6

Isotopic and geochemical assessment of travertine springs in northwestern Iran

Kaneko Masaki, Asahara Yoshihiro, Minami Masayo, Kurita Naoyuki, Azizi Hossein, Amin―Rasouli Hadi, Zhang Yubo

Abstracts of Annual Meeting of the Geochemical Society of Japan Vol. 67 ( 0 ) 2020

Data Descriptor: Daily observations of stable isotope ratios of rainfall in the tropics.

Scientific reports Vol. 9 ( 1 ) page： 14419 2019.10

Tritium, hydrogen and oxygen isotope compositions in monthly precipitation samples collected at toki, Japan

Akata N.

Radiation Protection Dosimetry Vol. 184 ( 3-4 ) page： 338-341 2019.10

Deciphering key processes controlling rainfall isotopic variability during extreme tropical cyclones.

Nature communications Vol. 10 ( 1 ) page： 4321 2019.9

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Papers - KURITA Naoyuki