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Water potential below a frozen soil layer was continuously monitored over an entire winter period (using thermally insulated tensiometers sheltered in a heated chamber) along with other soil, snow and atmospheric variables. In early winter, the freezing front advanced under a thin snow cover, inducing upward soil water flow in the underlying unfrozen soil. The freezing front started to retreat when the snow cover became thick enough to insulate the soil, resulting in the reversal of the flow direction in the unfrozen zone. These data provide a clear illustration of soil water dynamics, which have rarely been monitored with a tensiometer. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Eiichiro Kokubo Keiko Yoshinaga & Junichiro Makino 《Monthly notices of the Royal Astronomical Society》1998,297(4):1067-1072
We describe a P(EC) n Hermite scheme for planetary N -body simulation. The fourth-order implicit Hermite scheme is a time-symmetric integrator that has no secular energy error for the integration of periodic orbits with time-symmetric time-steps. In general N -body problems, however, this advantage is of little practical significance, since it is difficult to achieve time-symmetry with individual variable time-steps. However, we can easily enjoy the benefit of the time-symmetric Hermite integrator in planetary N -body systems, where all bodies spend most of the time on nearly circular orbits. These orbits are integrated with almost constant time-steps even if we adopt the individual time-step scheme. The P(EC) n Hermite scheme and almost constant time-steps reduce the integration error greatly. For example, the energy error of the P(EC)2 Hermite scheme is two orders of magnitude smaller than that of the standard PEC Hermite scheme in the case of an N = 100, m = 1025 g planetesimal system with the rms eccentricity 〈 e 2 〉1/2 ≲0.03. 相似文献
3.
Ken Yanagisawa Fumihiko Imamura Tsutomu Sakakiyama Tadashi Annaka Tomoyoshi Takeda Nobuo Shuto 《Pure and Applied Geophysics》2007,164(2-3):565-576
The present study focuses on evaluation of the maximum and minimum water levels caused by tsunamis as risk factors for operation
and management at nuclear power facilities along the coastal area of Japan. Tsunamis generated by submarine earthquakes are
examined, basing literature reviews and databases of information on historical tsunami events and run-up heights. For simulation
of water level along the coast, a numerical calculation system should be designed with computational regions covering a particular
site. Also the calculation system should be verified by comparison of historical and calculated tsunami heights. At the beginning
of the tsunami assessment, the standard faults, their locations, mechanisms and maximum magnitudes should be carefully estimated
by considering historical earthquake-induced tsunamis and seismo-tectonics at each area. Secondly, the range of errors in
the model parameters should be considered since earthquakes and tsunamis are natural phenomena that involve natural variability
as well as errors in estimating parameters. For these reasons, uncertainty-induced errors should be taken into account in
the process of tsunami assessment with parametric study of the tsunami source model. The element tsunamis calculated by the
standard fault models with the errors would be given for the design. Then, the design tsunami can be selected among the element
tsunamis with the most significant impact, maximum and minimum water levels, on the site, bearing in mind the possible errors
in the numerical calculation system. Finally, the design tsunami is verified by comparison with the run-up heights of historical
tsunamis, ensuring that the design tsunami is selected as the highest of all historical and possible future tsunamis at the
site. 相似文献
4.
Yukiyoshi Iwata Tomoyoshi Hirota Masaki Hayashi Shinji Suzuki Shuichi Hasegawa 《水文研究》2010,24(13):1755-1765
Despite the potential impact of winter soil water movements in cold regions, relatively few field studies have investigated cold‐season hydrological processes that occur before spring‐onset of snowmelt infiltration. The contribution of soil water fluxes in winter to the annual water balance was evaluated over 5 years of field observations at an agricultural field in Tokachi, Hokkaido, Japan. In two of the winters, soil frost reached a maximum depth of 0·2 m (‘frozen’ winters), whereas soil frost was mostly absent during the remaining three winters (‘unfrozen’ winters). Significant infiltration of winter snowmelt water, to a depth exceeding 1·0 m, occurred during both frozen and unfrozen winters. Such infiltration ranged between 126 and 255 mm, representing 28–51% of total annual soil water fluxes. During frozen winters, a substantial quantity of water (ca 40 mm) was drawn from deeper layers into the 0–0·2 m topsoil layer when this froze. Under such conditions, the progression and regression of the freezing front, regulated by the thickness of snow cover, controlled the quantity of soil water flux below the frozen layer. During unfrozen winters, 13–62 mm of water infiltrated to a depth of 0·2 m, before the spring snowmelt. These results indicate the importance of correctly evaluating winter soil water movement in cold regions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
Takahisa Furuichi Nobutomo Osanai Shin-ichiro Hayashi Norihiro Izumi Tomoko Kyuka Yasuhiro Shiono Tomoyoshi Miyazaki Tomoya Hayakawa Norihiro Nagano Naoki Matsuoka 《Landslides》2018,15(8):1645-1655
In August 2016, Typhoon 1610 (Lionrock) caused heavy rainfall in Hokkaido, which led to the discharge of a large volume of sediment and water from catchments on the eastern slope of the northern Hidaka Range. The eight catchments examined in this study are characterized by granitic lithology and late Pleistocene periglacial landforms with weakly cohesive, low-resistance periglacial debris thickly covering the weathered bedrocks. This characteristic of the landscape presumably provided a transport-limited condition where some debris flows were initiated by shallow landslides. As they moved, the debris flows grew larger through mobilization and erosion of sediment in channel beds and sidewalls. This sediment mobilization and erosion continued for an extensive distance along the course of the river. Morphological changes induced by channel aggradation and bank erosion were considerable and distinctive from upstream to downstream. Granitic periglacial sediments are amply present on the mountain slopes, river channels, and river banks in the area, likely due to the rarity of intensive rainfall events. These distinctive features of fossil periglacial catchments are important for disaster prevention and catchment-scale sediment management in sub-boreal areas, particularly in the context of climate change, which may generate more frequent and intensive rainfall events. 相似文献
6.
Masafumi Matsuyama Masaaki Ikeno Tsutomu Sakakiyama Tomoyoshi Takeda 《Pure and Applied Geophysics》2007,164(2-3):617-631
To study tsunami soliton fission and split wave-breaking, an undistorted experiment was carried out which investigated tsunami
shoaling on a continental shelf. Three models of the continental shelf were set up in a 205-m long 2-dimensional flume. Each
shelf model was 100 m, long with slopes of either 1/100, 1/150, or 1/200. Water surface elevations were measured across the
flume, including a dense cluster of wave gages installed around the point of wave-breaking. We propose new methods for calculating
wave velocity and the wave-breaking criterion based on our interpretation of time series data of water surface elevation.
At the point of wave-breaking, the maximum slope of water surface is between 20 to 50 deg., while the ratio of surface water
particle horizontal velocity to wave velocity is from 0.5 to 1.2. The values determined by our study are larger than what
has been reported by other researchers. 相似文献
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Yuichi Koike Yuzuru Nakaguchi Keizo Hiraki Terufumi Takeuchi Tomoyoshi Kokubo Takashi Ishimaru 《Journal of Oceanography》1993,49(6):641-656
A red tide due toGymnodinium nagasakiense was observed in August 1988 in Tanabe Bay, Wakayama Prefecture, Japan. The maximum cell concentration ofG. nagasakiense reached 1×105 cells ml–1 at the surface water. From May to September 1988, the following were monitored: water temperature, salinity, chlorophylla, D.O., dissolved nutrients (NO2–N, NO3–N, NH4–N, PO4–P DON, DOP), particulate nutrients (PON, POP) and three dissolved selenium species [Se(IV), Se(VI), Organic Se]. Dissolved inorganic nitrogen (NO3–N, NH4–N) decreased but PON, POP, DON, DOP and inorganic phosphate increased at the peak of the bloom. The concentration of organic selenium increased up to the bloom initiation period which started on 5 July, and then the concentration of Se(IV) increased as the concentration of organic selenium decreased at the peak of the bloom (3 August). The strong relationship was found between the concentration of Se(IV) and the cell concentration ofG. nagasakiense (r
2=0.98). The Se(IV) requirement ofG. nagasakiense was 2.89×10–17 moles cell–1, which was agreed well with 4.4×10–17 moles cell–1 found in a laboratory experiment onG. nagasakiense using selenium spiked artificial sea water medium. The average ratio of Se(IV) to dissolved inorganic nitrogen (DIN) during the red tide bloom was 11441, the ratio of Se(IV) to DIN at the surface with the maximum cell concentration ofG. nagasakiense of 1×105 cells ml–1 was 1137. These results suggested that selenium may play an important role in red tide outbreak ofG. nagasakiense. 相似文献
9.
Takehiko Hiwatari Kunio Shirasawa Yasushi Fukamachi Ryuichi Nagata Tomoyoshi Koizumi Hiroshi Koshikawa Kunio Kohata 《Polar Science》2008,2(1):41-54
Downward material fluxes under seasonal sea ice were measured using a time-series sediment trap installed at an offshore site in the Okhotsk Sea north of Hokkaido, Japan, from 13 January to 23 March 2005. The maximum fluxes of lithogenic material (753 mg m−2 day−1) and organic matter (mainly detritus; 333 mg m−2 day−1) were recorded during the period in which sea ice drifted ashore and increased in extent, from 13 January to 9 February. Organic matter as fecal pellets (81–93 mg m−2 day−1) and opal as biosilica (51–67 mg m−2 day−1), representing diatom fluxes, were abundant in sediment trap samples obtained during the period of full sea ice coverage from 10 February to 9 March. Microscopic observations revealed that fecal pellets were largely diatom frustules, suggesting that zooplankton actively grazed on ice algae during the period of full sea ice coverage. During the period of retreating sea ice, from 10 to 23 March, the phytoplankton flux showed a rapid increase (from 9.5 to 22.5 × 106 cells m−2 day−1), reflecting their release into the water column as the sea ice melted. Our results demonstrate that the quantity and quality of sinking biogenic and lithogenic materials vary with the seasonal extent of sea ice in mid-winter. 相似文献
10.
Tomoyoshi Takeuchi 《Marine Geodesy》2013,36(3-4):225-231
Abstract It is desired to track the location of an underwater data collecting platform using acoustic range data. A long‐range and high‐resolution acoustic system for underwater locating has been investigated. The system provides continuous and highly accurate tracking of a platform referenced to bottom‐mounted buoys. Each reference buoy contains an acoustic transponder, which is used to obtain ranging data from the transponder to the platform. The transponder has a signal source that is phase‐modulated by a maximal‐length binary sequence and a correlation processing unit to be capable of detecting received acoustic signals with high SNR in a noisy environment or in attenuation due to long‐range propagation, and to identify multipath acoustic signals. The acoustic system has been designed and sea tests tried. The results of that experiment have yielded capability of a submeter underwater acoustic positioning system. 相似文献
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