Data assimilation of sea ice concentration into a global ocean–sea ice model with corrections for atmospheric forcing and ocean temperature fields     

Takahiro Toyoda  Yosuke Fujii  Tamaki Yasuda  Norihisa Usui  Koji Ogawa  Tsurane Kuragano  Hiroyuki Tsujino  Masafumi Kamachi 《Journal of Oceanography》2016,72(2):235-262

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Influence of various factors on the difference in the liquid limit values determined by Casagrande’s and fall cone method     

Anil Kumar Mishra  Masami Ohtsubo  Loretta Y. Li  Takahiro Higashi 《Environmental Earth Sciences》2012,65(1):21-27

As there are many correlations linking the liquid limit directly or indirectly with various engineering properties of the soil, the accurate determination of the liquid limit is quite essential. Generally, two methods, i.e. Casagrande’s and fall cone are adopted to determine the liquid limit of soil. Research was carried out to study the influence of the properties of bentonite and the presence of the salt solution on the liquid limit values of soil-bentonite mixtures determined by the Casagrande’s and fall cone methods. The results showed that irrespective of the presence of the type of bentonite or salt solution, a higher value of the liquid limit was obtained by the Casagrande’s method as compared to the fall cone method. However, the difference between the two methods decreased with the decrease in the liquid limit, clay fraction, specific surface area and free swelling capacity of the bentonite present in the mixture. Similarly, the difference in the liquid limit values obtained by both these methods is reduced with an increase in the salt concentration.  相似文献   

Historical record of heavy metal pollution deduced by lead isotope ratios in core sediments from the Osaka Bay,Japan     

Takahiro Hosono  Chih-Chieh Su  Kei Okamura  Makoto Taniguchi 《Journal of Geochemical Exploration》2010

Three marine sediment cores from Osaka Bay were analyzed for ²¹⁰Pb geochronology, heavy metal concentrations (Zn, Cu, and Pb) and stable lead isotope ratios (²⁰⁶Pb/²⁰⁷Pb) in order to reconstruct high-resolution heavy metal pollution history from 1900–2006. Anthropogenic metal accumulation in sediments peaked in 1970 in agreement with the high economic growth period in Japan. The comparison of temporal patterns of ²⁰⁶Pb/²⁰⁷Pb ratio with other areas of Japan suggested that the heavy metals, imported from several different countries during the periods of economic growth (1955 to 1973), are the main pollution source for the country. For the period 1970–2006, the sediment data reflect the result of stricter environmental regulations applied after the late 1960s. However, heavy metal concentrations in the surface sediments are still elevated to levels several times higher than the levels at the bottoms of the cores. Additionally, the lead isotope ratio does not show significant change after the 1980s. Secondary heavy metal pollution through the mixing of deeper polluted sediment appears to be the likely reason for the deterioration of present time submarine sediment environments. In conclusion, this study has demonstrated that it is difficult to recover over a period of several years the benthic quality of a bay, once it is heavily polluted.  相似文献   

High-resolution imaging polarimetry of HL Tau and magnetic field structure     

P. W. Lucas  Misato Fukagawa  Motohide Tamura  A. F. Beckford  Yoichi Itoh  Koji Murakawa  Hiroshi Suto  Saeko S. Hayashi  Yumiko Oasa  Takahiro Naoi  Yoshiyuki Doi  Noboru Ebizuka  Norio Kaifu 《Monthly notices of the Royal Astronomical Society》2004,352(4):1347-1364

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Global mantle heterogeneity and its influence on teleseismic regional tomography     

Dapeng Zhao  Yoshihiro Yamamoto  Takahiro Yanada 《Gondwana Research》2013,23(2):595-616

A new global P-wave tomography model is determined using a flexible-grid parameterization. This new model better reveals the mantle structure under the polar regions than the previous tomographic models. The subducting slabs are generally imaged clearly as high-velocity (high-V) zones. The young slabs are still subducting in the upper mantle and the mantle transition zone (MTZ), whereas the old and ancient slabs are either stagnant in the MTZ or have subducted down to the lower mantle, even reaching the core-mantle boundary. Low-velocity (low-V) anomalies are generally revealed in the mantle under the hotspot regions. It seems that a variety of mantle upwelling (plumes) exist. Some strong plumes are visible in the whole mantle under the long-living hotspots, such as those in south-central Pacific, Africa, Hawaii and Iceland, whereas weak plumes are visible in only some depth range under the minor hotspots. Under the intraplate volcanoes in East Eurasia, Bering Sea and West Alaska, significant low-V anomalies are revealed in the upper mantle, which may reflect hot and wet upwelling associated with corner flows in the big mantle wedge (BMW) above the stagnant Pacific slab in the MTZ and perhaps deep slab dehydration as well. The subduction-triggered magmatism in the BMW may be a new class of mantle plumes. We also used the new global model to investigate the influence of whole-mantle heterogeneity on the determination of upper-mantle tomography under Japan with a teleseismic inversion method. The results show that the mantle heterogeneities outside the target volume of regional tomography can cause significant changes (~ 0.2-0.4 s) to the observed relative travel-time residuals of a distant earthquake. The pattern of regional tomography remains the same even after correcting for the whole-mantle heterogeneity, but there are some changes in the amplitude of velocity anomalies in the regional tomography. Hence it is necessary to correct for the mantle heterogeneities outside the target volume so as to obtain a better regional tomography.  相似文献   

Rainfall–runoff–inundation analysis of the 2010 Pakistan flood in the Kabul River basin     

Takahiro Sayama  Go Ozawa  Takahiro Kawakami  Seishi Nabesaka  Kazuhiko Fukami 《水文科学杂志》2013,58(2):298-312

Abstract

Pakistan has suffered a devastating flood disaster in 2010. In the Kabul River basin (92 605 km²), large-scale riverine and flash floods caused destructive damage with more than 1100 casualties. This study analysed rainfall–runoff and inundation in the Kabul River basin with a newly developed model that simulates the processes of rainfall–runoff and inundation simultaneously based on two-dimensional diffusion wave equations. The simulation results showed a good agreement with an inundation map produced based on MODIS for large-scale riverine flooding. In addition, the simulation identified flash flood-affected areas, which were confirmed to be severely damaged based on a housing damage distribution map. Since the model is designed to be used even immediately after a disaster, it can be a useful tool for analysing large-scale flooding and to provide supplemental information to agencies for relief operations.

Editor Z.W. Kundzewicz

Citation Sayama, T., Ozawa, G., Kawakami, T., Nabesaka, S. and Fukami, K., 2012. Rainfall–runoff–inundation analysis of the 2010 Pakistan flood in the Kabul River basin. Hydrological Sciences Journal, 57 (2), 298–312.  相似文献   

Olivine-rich exposures in the South Pole-Aitken Basin     

Satoru Yamamoto  Ryosuke Nakamura  Tsuneo Matsunaga  Yoshiko Ogawa  Yoshiaki Ishihara  Tomokatsu Morota  Naru Hirata  Makiko Ohtake  Takahiro Hiroi  Yasuhiro Yokota  Junichi Haruyama 《Icarus》2012,218(1):331-344

The distribution and the geological context of the olivine-rich exposures in the South Pole-Aitken (SPA) Basin on the Moon were investigated based on the spectral data obtained from the Spectral Profiler (SP) and Multiband Imager (MI) onboard the Japanese lunar explorer Kaguya/SELENE. The olivine-rich exposures are found only in the peak rings or central peaks of the Schrödinger basin and Zeeman crater, which are located in the outer region of the SPA Basin and not in the center region. On a localized scale, the olivine-rich materials are exposed on landslide features on the crater walls or sloped wall of the central peaks or the peak rings. Another observational finding is the co-existence of olivine-rich and plagioclase-rich materials on a kilometer scale spanning most of the olivine-rich sites in the Schrödinger basin. Pyroxene-rich materials are found in fresh craters outside the peak rings or the central peaks with olivine-rich materials. Based on these results, the following scenario are proposed: (1) the impact to form the SPA Basin melted a large amount of the lunar upper mantle and crust, and distributed the melted materials to the outer region; (2) local differentiation of melted materials hid the olivine-rich materials in the center region of the SPA Basin; (3) later impacts that formed the Schrödinger and Zeeman craters excavated and exposed the olivine-rich materials to the surface again; and (4) space weathering and regolith gardening obscured the olivine-rich spectra at the exposure sites, but recent, small scale impacts or landslides on the sloped wall exposed fresh olivine-rich materials, allowing the identification of the olivine-rich exposures by spectral remote-sensing. This suggests that several, different scale events play an important role in forming the surface distributions of originally deep-seated materials on the Moon, as well as on other planetary bodies.  相似文献   

Projection of extreme flood inundation in the Mekong River basin under 4K increasing scenario using large ensemble climate data     

Sophal Try  Shigenobu Tanaka  Kenji Tanaka  Takahiro Sayama  Maochuan Hu  Ty Sok  Chantha Oeurng 《水文研究》2020,34(22):4350-4364

Projecting changes in the frequency and intensity of future precipitation and flooding is critical for the development of social infrastructure under climate change. The Mekong River is among the world's large-scale rivers severely affected by climate change. This study aims to define the duration of precipitation contributing to peak floods based on its correlation with peak discharge and inundation volume in the Lower Mekong Basin (LMB). We assessed the changes in precipitation and flood frequency using a large ensemble Database for Policy Decision-Making for Future Climate Change (d4PDF). River discharge in the Mekong River Basin (MRB) and flood inundation in the LMB were simulated by a coupled rainfall-runoff and inundation (RRI) model. Results indicated that 90-day precipitation counting backward from the day of peak flooding had the highest correlation with peak discharge (R² = .81) and inundation volume (R² = .81). The ensemble mean of present simulation of d4PDF (1951–2010) showed good agreement with observed extreme flood events in the LMB. The probability density of 90-day precipitation shifted from the present to future climate experiments with a large variation of mean (from 777 to 900 mm) and SD (from 57 to 96 mm). Different patterns of sea surface temperature significantly influence the variation of precipitation and flood inundation in the LMB in the future (2051–2110). Extreme flood events (50-year, 100-year, and 1,000-year return periods) showed increases in discharge, inundation area, and inundation volume by 25%–40%, 19%–36%, and 23%–37%, respectively.  相似文献   

影响日本佐渡岛农民实施野生动物友好型耕作的因素探究(英文)     

中村慧  柘植隆宏  大久保悟  武内和彦  西川潮 《资源与生态学报(英文版)》2014,5(4):370-380

野生动物友好型耕作(Wildlife-friendly Farming,WFF)实践是一种维持农田生态恢复的良好方式。本研究的目的在于探讨影响日本佐渡岛农民实施WFF的因素和提出影响这种实践传播的政策。对佐渡岛上把大米销售给日本农业合作社(Japan Agricultural Cooperatives,JA)的5010个农户进行了问卷调查,总共收到2231农户反馈问卷(反馈率45%)。通过与未经认证农民的态度和属性对比,我们确定了影响农民实施WFF的关键因素。与未经认证的农民相比,已认证的农民:(1)对生物多样性和WFF的经济效益表现出更高的兴趣;(2)拥有更多的已认证农民朋友;(3)感受到了来自消费者的更多的压力和期望;(4)当实施WFF时,不受恶劣劳动力或农田条件的限制。为了在佐渡岛进一步宣传WFF,我们建议把WFF实践对稻田生物多样性的有效性信息应用到公共教育中,并在非认证农民和已认证农民之间、农民与消费者之间创建交流的机会。  相似文献   

A new one-dimensional simple energy balance and carbon cycle coupled model for global warming simulation     

Kazutaka Murakami  Takahiro Sasai  Yasushi Yamaguchi 《Theoretical and Applied Climatology》2010,101(3-4):459-473

Global warming and accompanying climate change may be caused by an increase in atmospheric greenhouse gasses generated by anthropogenic activities. In order to supply such a mechanism of global warming with a quantitative underpinning, we need to understand the multifaceted roles of the Earth's energy balance and material cycles. In this study, we propose a new one-dimensional simple Earth system model. The model consists of carbon and energy balance submodels with a north–south zonal structure. The two submodels are coupled by interactive feedback processes such as CO₂ fertilization of net primary production (NPP) and temperature dependencies of NPP, soil respiration, and ocean surface chemistry. The most important characteristics of the model are not only that the model requires a relatively short calculation time for carbon and energy simulation compared with a General Circulation Model (GCM) and an Earth system Model of Intermediate Complexity (EMIC), but also that the model can simulate average latitudinal variations. In order to analyze the response of the Earth system due to increasing greenhouse gasses, several simulations were conducted in one dimension from the years 1750 to 2000. Evaluating terrestrial and oceanic carbon uptake output of the model in the meridional direction through comparison with observations and satellite data, we analyzed the time variation patterns of air temperature in low- and middle-latitude belts. The model successfully reproduced the temporal variation in each latitude belt and the latitudinal distribution pattern of carbon uptake. Therefore, this model could more accurately demonstrate a difference in the latitudinal response of air temperature than existing models. As a result of the model evaluations, we concluded that this new one-dimensional simple Earth system model is a good tool for conducting global warming simulations. From future projections using various emission scenarios, we showed that the spatial distribution of terrestrial carbon uptake may vary greatly, not only among models used for climate change simulations, but also amongst emission scenarios.  相似文献