A multi‐geochronological study of the Hakusan volcano,central Japan          下载免费PDF全文

Noriko Hasebe  Yasuyuki Nakano  Hikaru Miyamoto  Toshio Higashino  Akihiro Tamura  Shoji Arai  Ju‐Yong Kim 《Island Arc》2016,25(2):111-125

The Hakusan volcano, central Japan, is located in a region where two subducting plates (the Pacific Plate and the Philippine Sea Plate) overlap near the junction of four plates adjacent to the Japanese Islands (the Pacific Plate, the Philippine Sea Plate, the Eurasia Plate, and the North American Plate). The Hakusan volcano consists of products from four major volcanic episodes: Kagamuro, Ko‐hakusan, and Shin‐Hakusan I and II. To date the eruption events of the Hakusan volcano we applied thermoluminescence and fission track methods. ²³⁸U(²³⁴U)–²³⁰Th disequilibrium and ²⁰⁶Pb/²³⁸U methods were applied to date the zircon crystallization ages for estimating the magma residence time before the eruptions. The eruption ages we obtained are ca 250 ka for Kagamuro, ca 100 ka and ca 60 ka for Ko‐Hakusan, ca 50 ka for Shin‐Hakusan I, and <10 ka for Shin‐Hakusan II. They are concordant with previous reports based on K–Ar dating. Some of the pyroclastic rocks, possibly originating from Shin‐Hakusan II activities, are dated to be ca 36 ka or 50 ka, and belong to the Shin‐Hakusan I activity. The zircon crystallization ages show several clusters prior to eruption. The magma residence time was estimated for each volcanic activity by comparing the major crystallization events and eruption ages, and we found a gradual decrease from ca. 500 ky for the Kagamuro activity to ca. 5 ky for the Shin‐Hakusan II activity. This decrease in residence time may be responsible for the decrease in volume of erupted material estimated from the current topography of the region. The scale of volcanic activity, which was deduced from the number of crystallized zircons, is more or less constant throughout the Hakusan volcanic activity. Therefore, the decrease in magma residence time is most likely the result of stress field change.  相似文献   

Parallel/Vector Integration Methods for Dynamical Astronomy     

Toshio Fukushima 《Celestial Mechanics and Dynamical Astronomy》1999,73(1-4):231-241

This paper reviews three recent works on the numerical methods to integrate ordinary differential equations (ODE), which are specially designed for parallel, vector, and/or multi-processor-unit(PU) computers. The first is the Picard-Chebyshev method (Fukushima, 1997a). It obtains a global solution of ODE in the form of Chebyshev polynomial of large (> 1000) degree by applying the Picard iteration repeatedly. The iteration converges for smooth problems and/or perturbed dynamics. The method runs around 100-1000 times faster in the vector mode than in the scalar mode of a certain computer with vector processors (Fukushima, 1997b). The second is a parallelization of a symplectic integrator (Saha et al., 1997). It regards the implicit midpoint rules covering thousands of timesteps as large-scale nonlinear equations and solves them by the fixed-point iteration. The method is applicable to Hamiltonian systems and is expected to lead an acceleration factor of around 50 in parallel computers with more than 1000 PUs. The last is a parallelization of the extrapolation method (Ito and Fukushima, 1997). It performs trial integrations in parallel. Also the trial integrations are further accelerated by balancing computational load among PUs by the technique of folding. The method is all-purpose and achieves an acceleration factor of around 3.5 by using several PUs. Finally, we give a perspective on the parallelization of some implicit integrators which require multiple corrections in solving implicit formulas like the implicit Hermitian integrators (Makino and Aarseth, 1992), (Hut et al., 1995) or the implicit symmetric multistep methods (Fukushima, 1998), (Fukushima, 1999). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

North Pacific Tropical Water: its climatology and temporal changes associated with the climate regime shift in the 1970s   总被引：2，自引：0，他引：2  

Toshio Suga  Ayato Kato  Kimio Hanawa 《Progress in Oceanography》2000,47(2-4)

North Pacific Tropical Water (NPTW) is characterized as a subsurface salinity maximum flowing in the North Equatorial Current and is the main source of salt for the North Pacific. We briefly describe the climatological features of its formation and circulation, and then examine temporal changes in its properties associated with the climate regime shift in the 1970s. We use a variety of data, which include the repeat hydrographic sections along 130°E, 137°E, 144°E and 155°E meridians, the hydrographic data from the Hawaii Ocean Time-series, the World Ocean Atlas 1994, and available gridded data of wind stress and evaporation. The classical idea that NPTW originates from the zone of the highest sea surface salinity at 20°–30°N centered around the international date line and spreads along the isopycnal geostrophic flow patterns is confirmed. Further, it is shown that the meridional extent of NPTW along 137°E is from 10°N to 23°N on average and the highest salinity core lies at about 15°N and 24.0σ_θ, and that the portion of NPTW north (south) of about 15°N originates from the formation region west (east) of the date line. NPTW in the 137°E section changed remarkably associated with the mid-1970s regime shift. North of 15°N NPTW increased both in its salinity and thickness while to the south of 15°N only its salinity increased and its thickness remained unchanged. The westward geostrophic velocity is increased significantly in both the southern and northern parts of NPTW. The northern thickening and speedup and the southern speedup increased NPTW transport across 137°E. The changes in the thermohaline forcing such as evaporation and Ekman salt convergence in the NPTW formation region possibly contributed to the increases in salinity in the southern part of NPTW, but not to that of the northern part. On the other hand, the increased Ekman pumping accounts for the increase of the NPTW inventory and transport at 137°E. The increased salinity of NPTW at 137°E, especially its northern portion, was presumably caused by an increase in its formation rate rather than changes in the sea surface salinity in its formation region; the thicker the NPTW layer is, the saltier is the core that tends to survive the mixing processes.  相似文献   

Forty-five years of oceanographic and meteorological observations at a coastal station in the NW Mediterranean: a ground truth for satellite observations     

Salat  Jordi  Pascual  Josep  Flexas  Mar  Chin  Toshio Michael  Vazquez-Cuervo  Jorge 《Ocean Dynamics》2019,69(9):1067-1084

Ocean Dynamics - Marine and atmospheric parameters, including temperature observations from surface to 80&nbsp;m (at 6 depths) are measured since September 1973 on a higher-than-weekly...  相似文献   

Fifty years of the 137°E repeat hydrographic section in the western North Pacific Ocean     

Eitarou Oka  Masao Ishii  Toshiya Nakano  Toshio Suga  Shinya Kouketsu  Masatoshi Miyamoto  Hideyuki Nakano  Bo Qiu  Shusaku Sugimoto  Yusuke Takatani 《Journal of Oceanography》2018,74(2):115-145

The 137°E repeat hydrographic section of the Japan Meteorological Agency across the western North Pacific was initiated in 1967 as part of the Cooperative Study of the Kuroshio and Adjacent Regions and has been continued biannually in winter and summer. The publicly available data from the section have been widely used to reveal seasonal to decadal variations and long-term changes of currents and water masses, biogeochemical and biological properties, and marine pollutants in relation to climate variability such as the El Niño-Southern Oscillation and the Pacific Decadal Oscillation. In commemoration of the 50th anniversary in 2016, this review summarizes the history and scientific achievements of the 137°E section during 1967–2016. Through the publication of more than 100 papers over this 50-year span, with the frequency and significance of the publication increasing in time, the 137°E section has demonstrated its importance for future investigations of physical–biogeochemical–biological interactions on various spatiotemporal scales, and thereby its utility in enhancing process understanding to aid projections of the impact of future climate change on ocean resources and ecosystems over the twenty-first century.  相似文献   

Poleward propagation of boreal summer intraseasonal oscillations in a coupled model: role of internal processes     

R. S. Ajayamohan  H. Annamalai  Jing-Jia Luo  Jan Hafner  Toshio Yamagata 《Climate Dynamics》2011,37(5-6):851-867

The study compares the simulated poleward migration characteristics of boreal summer intraseasonal oscillations (BSISO) in a suite of coupled ocean?Catmospheric model sensitivity integrations. The sensitivity experiments are designed in such a manner to allow full coupling in specific ocean basins but forced by temporally varying monthly climatological sea surface temperature (SST) adopted from the fully coupled model control runs (ES10). While the local air?Csea interaction is suppressed in the tropical Indian Ocean and allowed in the other oceans in the ESdI run, it is suppressed in the tropical Pacific and allowed in the other oceans in the ESdP run. Our diagnostics show that the basic mean state in precipitation and easterly vertical shear as well as the BSISO properties remain unchanged due to either inclusion or exclusion of local air?Csea interaction. In the presence of realistic easterly vertical shear, the continuous emanation of Rossby waves from the equatorial convection is trapped over the monsoon region that enables the poleward propagation of BSISO anomalies in all the model sensitivity experiments. To explore the internal processes that maintain the tropospheric moisture anomalies ahead of BSISO precipitation anomalies, moisture and moist static energy budgets are performed. In all model experiments, advection of anomalous moisture by climatological winds anchors the moisture anomalies that in turn promote the northward migration of BSISO precipitation. While the results indicate the need for realistic simulation of all aspects of the basic state, our model results need to be taken with caution because in the ECHAM family of coupled models the internal variance at intraseasonal timescales is indeed very high, and therefore local air?Csea interactions may not play a pivotal role.  相似文献   

Estimation of indirect economic loss caused by house destruction in a natural disaster     

Toshio Fujimi  Hirokazu Tatano 《Natural Hazards》2012,61(3):1367-1388

Designing appropriate post-disaster emergency and recovery housing policies requires accurate estimation of the indirect or “flow” loss generated by the involuntary displacement of households to housing other than their own destroyed homes. We employed the stated choice method to measure residence choice following a hypothetical disaster in a procedure developed to estimate flow loss due to house destruction. This method was applied to households in the city of Nagaoka in Niigata Prefecture to estimate flow loss for a range of residence types and residence attributes following relocation. The results revealed that the relocation residence type itself (such as a shelter, temporary dwelling, rental housing, or one’s own home) had a substantial effect on residence choice. Regarding residence attributes, residential expenses such as rent, housing loans, and spaciousness had a significant effect on residence choice. Moreover, we found that respondents placed a very high value on living in their own home compared with other residence types, indicating that subsidizing the prompt repair and rebuilding of private homes is likely to be an effective recovery support policy. In addition, a cost–benefit analysis of our results revealed that rent subsidies are more efficient than the construction of public housing as a means of financially assisting economically constrained households after a disaster.  相似文献   

Recursive computation of oblate spheroidal harmonics of the second kind and their first-, second-, and third-order derivatives   总被引：1，自引：0，他引：1  

Toshio Fukushima 《Journal of Geodesy》2013,87(4):303-309

A recursive method is developed to compute the ratios of the oblate spheroidal harmonics of the second kind and their first-, second-, and third-order derivatives. The recurrence formulas consist of three kinds: (1) fixed-degree increasing-order, (2) mixed-degree increasing-order, and (3) fixed-order decreasing-degree. The three seed values are evaluated by rapidly convergent series. The derivatives of the ratios are recursively obtained from the values and lower-order derivatives of the same harmonic order and of the same or higher degrees. The new method precisely and quickly computes the ratios and their low-order derivatives. It provides 13 correct digits of the ratios of degree as high as 262,000 and runs 20–100 times faster than the existing methods.  相似文献   

Diurnal variation of CO₂ concentration, Δ¹⁴C and δ¹³C in an urban forest: estimate of the anthropogenic and biogenic CO₂ contributions     

Hiroshi A. Takahashi  Eiichi Konohira  Tetsuya Hiyama  Masayo Minami  Toshio Nakamura  Naohiro Yoshida 《Tellus. Series B, Chemical and physical meteorology》2002,54(2):97-109

Diurnal variation in the atmospheric CO₂ concentration and the carbon isotopic composition (Δ¹⁴C and δ¹³C) was measured in a forest in an urban area on 9 February 1999. The carbon isotope approach used in the present study differentiated between the quantitative contributions from anthropogenic and biogenic CO₂ sources in the urban atmosphere. The anthropogenic (fossil fuel) and biogenic (soil respiration) contributions was estimated, and they ranged from 1 to 16% and from 2 to 8% of the total atmospheric CO₂. The diurnal variation of the anthropogenic CO₂ was the major cause of the total atmospheric CO₂ variation, while the biogenic CO₂ remained relatively constant throughout the day. Estimating the contribution of soil respired CO₂ provided the mean residence time of soil respired CO₂ within the forest atmosphere.  相似文献   

Sedimentary organic matter contents and porewater chemistry at upper bathyal depths influenced by the 2011 off the Pacific coast of Tohoku Earthquake and tsunami     

Hidetaka Nomaki  Kazuno Arai  Hisami Suga  Takashi Toyofuku  Masahide Wakita  Takuro Nunoura  Kazumasa Oguri  Takafumi Kasaya  Shuichi Watanabe 《Journal of Oceanography》2016,72(1):99-111

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