Factors affecting dominant peak-flow runoff-generation mechanisms among five neighbouring granitic headwater catchments     

Kenta Iwasaki  Masanori Katsuyama  Makoto Tani 《水文研究》2020,34(5):1154-1166

We examined how and why dominant peak-flow runoff-generation mechanisms differ among neighbouring headwater catchments. We monitored runoff and groundwater levels and performed terrain analyses in a granitic second-order catchment and its four neighbouring subcatchments in the Kiryu Experimental Watershed in Japan. Our analysis of lag times from peak rainfall to peak runoff suggests differences in the dominant peak-flow runoff-generation mechanisms among the five catchments. For two of the three zero-order catchments, with few perennial groundwater bodies, subsurface flow from hillslopes was the dominant mechanism at some events. However, the dominant mechanisms were channel precipitation and riparian runoff at almost all events in first- and second-order catchments and in the third zero-order catchment, which has a large perennial groundwater body over a bedrock depression in the riparian zone. In this zero-order catchment, the quick-flow ratio was the smallest of the five catchments because subsurface flow from the hillslope was buffered at the riparian zone. These facts suggest that the channel length, riparian buffering, and hillslope connectivity were the factors governing the different dominant peak-flow runoff-generation mechanisms among the catchments. Riparian buffering was affected, not only by surface topography, but also by bedrock topography and bedrock groundwater (BGW) dynamics. Our findings indicate that both of BGW dynamics and topography are important for catchment classification, and the relative importance of topography increases with the change from baseflow to stormflow. Furthermore, mismatching between a geographic source and a flow path resulted in different catchment classifications depending on the approach. Therefore, multiple approaches during both baseflow and stormflow periods are necessary for catchment classification to apply information obtained from one headwater catchment to other headwater catchments within the same region.  相似文献   

Crustal Structure Beneath Lofoten, N. Norway, From Vertical Incidence and Wide-Angle Seismic Data   总被引：1，自引：0，他引：1  

R. Mjelde  M. A. Sellevoll  H. Shimamura  T. Iwasaki  T. Kanazawa 《Geophysical Journal International》1993,114(1):116-126

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Al-related centers in relation to γ-irradiation     

Pedro L. Guzzo  Fumiko Iwasaki  Hideo Iwasaki 《Physics and Chemistry of Minerals》1997,24(4):254-263

 The charge compensation problem for Si−Al substitution in Brazilian natural quartz is investigated in relation to γ-irradiation darkening response and impurity contents evaluated by atomic absorption spectrometry and infrared absorption spectroscopy. Al⁺³ in as-grown natural quartz is compensated by Li⁺ and H⁺ to form Al−Li and Al−OH centers. The content ratios (Al−Li)/(Al−OH) and Li/(broad OH band) depend on the environmental conditions of crystal growth and influence the formation of Al-hole centers due to γ-irradiation. Al−OH centers are the dominant Al-related centers in quartz from hydrothermal origin while Al−Li centers are dominant for that of pegmatitic origin. The formation of Al-hole centers is little in quartz with a high content of broad OH band which is from low temperature hydrothermal origin. Received May 23, 1995 / Revised, accepted May 8, 1996  相似文献   

Isoprenoids of Okinawan mangroves as lipid input into estuarine ecosystem     

Mohammad Basyuni  Hirosuke Oku  Shigeyuki Baba  Kensaku Takara  Hironori Iwasaki 《Journal of Oceanography》2007,63(4):601-608

Isoprenoids in the nonsaponifiable lipids (NSL) fraction of Okinawan mangroves were analyzed with special reference to their importance as lipid input into estuarine ecosystems. Triterpenoids and phytosterols comprised the major proportion of NSL. Identifications of the triterpenoids and phytosterols in NSL fraction were based on the interpretation of ¹³C-NMR and GC-MS spectra. The triterpenoids and phytosterols mainly comprised 11 and 6 compounds, respectively. The major components were lupeol, β-amyrin and taraxerol for triterpenoids, and β-sitosterol and stigmasterol for phytosterols. The diversity in the terpenoid composition was noted in both leaves and roots of mangrove species, implying the chemotaxonomic utility of terpenoids. Terpenoid compositions of the root are not always similar to that of leaf, suggesting that terpenoids in the root are produced by biosynthesis in situ, not by translocation of the synthate from the leaf. Terpenoids existed in greater proportion in the outer parts of the root. These data are likely to contribute to estimating the lipid input from mangrove trees adjacent to estuarine sediments and the ocean.  相似文献   

Emergence Patterns of Small Subtidal Arthropods in Relation to Day/Night, Tidal, and Surface/Bottom Factors: Investigations in the Boreal Sea, Japan (Akkeshi, Hokkaido)     

Masayuki Saigusa  Kazushi Oishi  Akihiro Ikumoto  Hiroshi Iwasaki  Michihiro Terajima 《Journal of Oceanography》2000,56(3):295-310

The emergence of small arthropods was studied in the boreal sea, Japan (Akkeshi, Hokkaido). In the shallow subtidal zone, two impeller pumps were set in the surface and bottom waters. The pumps ran continuously for 25 days (22 August-16 September, 1998), and invertebrates were sampled using a nylon net (300 to 500 m in mesh size). The small arthropods collected with the net belonged to 16 orders comprising about 60 taxa. In the dominant 23 taxa, a two-way ANOVA was applied to determine whether there was any significant difference in abundance between day and night and between surface and bottom. While emergence of 15 taxa (65%) was significantly different with regard to the day/night factor, that of the other 8 taxa (35%) was not. As to the difference between the two depths, the distribution of 15 taxa (65%) was significantly different. Furthermore, in 25 taxa for which over 100 specimens were collected in each of the two depths of water, emergence patterns were examined with regard to the synchrony with day/night and tidal cycles. There were various nocturnal patterns, and the strength of the synchrony with the day/night cycle was different for each species or group. Within the same taxa, nocturnal patterns were more clearly manifested in the surface water than in the bottom water. A tidal rhythm of emergence was only seen in zoeas of shrimp. Variations of the emergence patterns of benthic crustaceans are accounted for by a hypothesis that the frequency of swimming during day versus at night is different in each species. On the other hand, the emergence patterns of some zooplankton reflect by the daily rhythm of vertical migration or dispersal in the water column.  相似文献   

The ocean/continent transition along a profile through the Lofoten basin,Northern Norway     

Andreas Goldschmidt-Rokita  Knut J. F. Hansch  Hans B. Hirschleber  Takaya Iwasaki  Toshihiko Kanazawa  Hideki Shimamura  Markvard A. Sellevoll 《Marine Geophysical Researches》1994,16(3):201-224

The Cenozoic margins of the Norwegian-Greenland Sea offer ideal conditions for passive margin studies. A series of structural elements, first observed on these margins, led to the concept of volcanic passive margins. Questions still remain about the development of such features and the location of the boundary between oceanic and continental crust. Despite the thin sediment cover of the margins, seismic reflection data are not able to image the deeper structures due to the occurrence of igneous rocks at shallow depth.This paper presents a 320-km long profile perpendicular to the strike of the main structural units of the Lofoten Margin in Northern Norway. A geological model is proposed, based on observations made with ocean bottom seismographs, which recorded seismic refraction data and wide angle reflections, along with a seismic reflection profile covering the same area. Ray-tracing was used to calculate a geophysical model from the shelf area into the Lofoten basin. The structures typical of a volcanic passive margin were found, showing that the Lofoten Margin was influenced by increased volcanic activity during its evolution. The ocean/continent transition is located in a 30-km wide zone landwards of the Vøring Plateau escarpment.The whole margin is underlain by a possibly underplated, high velocity layer. Evidence for a pre-rift sediment basin landwards of the escarpment, overlain by basalt flows, was seen. These structural features, related to extensive volcanism on the Lofoten Margin, are not as distinct as further south along the Norwegian Margin. Viewed in the light of the hot-spot theory of White and McKenzie (1989) the Lofoten Margin can be interpreted as a transitional type between volcanic and non-volcanic passive margin.  相似文献   

Studies on the red tide flagellates—VI     

H. Iwasaki 《Journal of Oceanography》1971,27(4):152-157

Extensive bloom of red tide, accompanying mass mortality of fish and the other animals, occurred in Bingo-Nada, the Seto Inland Sea, in August, 1970. Two species of microorganisms,Eutreptiella sp. andExuviaella sp., were isolated from the water and were obtained in axenic culture by micropipette washings.These organisms are stimulated by trace metals. The highest growth resulted from the addition of chelated Fe (<3 mg/l) or/and Mn (<2 mg/l) to enriched sea water. The organisms prefer low salinity. The optimal salinities are Cl 8.0–17.0 forEutreptiella sp., Cl >11.0 forExuviaella sp. respectively. These organisms can tolerate a wide range of pH.Exuviaella sp. needs vitamin B₁₂ for growth. The pattern of specificity toward B₁₂ analogues²⁾ is similar to that ofEuglena gracilis. On the other hand,Eutreptiella sp. requires B₁₂, biotin, and thiamine. The B₁₂ specificity fits toEscherichia coli. Both organisms prefer NH₄-N in lower concentrations than 1 mg/l (optimal 0.3 mg/l) as nitrogen sources.Exuviaella sp. also likes urea. Inorganic and organic phosphates are utilized by the organisms:Eutreptiella sp. utilizes Na₂-glycerophosphate, guanylic acid,Exuviaella sp. utilizes Na₂-glycerophosphate, adenylic acid. KH₂PO₄ is the most favorable to the growth of both organisms. All the purines, pyrimidines, plant hormones tested increase the growth ofExuviaella sp. Especially, guanine, xanthine, thymine, indoleacetic acid, and gibberellic acid promote the growth remarkably.These organisms do not grow to high densities without Fe or/and Mn in high concentrations even under the conditions provided by optimal temperature, salinities, pH, and essential nutrients. On the other hand, the coastal area of Fukuyama where the red tide first occurred has been fertilized with the nutrients essential to the organisms, and also polluted with trace metals such as Fe (Iwasaki, Inoue unpublished data). From these results, it can be considered that the great increase of the organisms is caused principally by the high concentration of iron in the sea water.  相似文献   

Temporal Variability of High Vertical Wavenumber Shear over the Izu-Ogasawara Ridge     

Maki?NagasawaEmail author  Toshiyuki?Hibiya  Naoki?Furuichi  Shogo?Takagi 《Journal of Oceanography》2005,61(6):1101-1105

Recent numerical studies (Hibiya et al., 1996, 1998, 2002) showed that the energy cascade across the internal wave spectrum down to small dissipation scales was under strong control of parametric subharmonic instabilities (PSI) which transfer energy from low vertical mode double-inertial frequency internal waves to high vertical mode near-inertial internal waves. To see whether or not the numerically-predicted energy cascade process is actually dominant in the real deep ocean, we examine the temporal variability of vertical profiles of horizontal velocity observed by deploying a number of expendable current profilers (XCPs) at one location near the Izu-Ogasawara Ridge. By calculating EOFs, we find the observed velocity profiles are dominated by low mode semidiurnal (∼double-inertial frequency) internal tides and high mode near-inertial internal waves. Furthermore, we find that the WKB-stretched vertical scales of the near-inertial current shear are about 250 sm and 100 sm. The observed features are reasonably explained if the energy cascade down to small dissipation scales is dominated by PSI.  相似文献   

A dataset of continental river discharge based on JRA-55 for use in a global ocean circulation model     

Tatsuo Suzuki  Dai Yamazaki  Hiroyuki Tsujino  Yoshiki Komuro  Hideyuki Nakano  Shogo Urakawa 《Journal of Oceanography》2018,74(4):421-429

A dataset of historical river discharge into oceans was created using the CaMa-Flood global river routing model and adjusted runoff from the land component of JRA-55. The major rivers were well resolved with a 0.25° horizontal resolution. The total runoff on each drainage basin exhibits a distinctive bias on decadal time scales. The input runoff data were modified using 5-year low-pass-filtered multiplicative factors to fit the annual mean climatology and decadal variations in the reference dataset. The model incorporated data from 1958 to 2016. The yearly and seasonal variations of the major rivers are well represented by the model.  相似文献   

Electric and magnetic field of a direct-current source in a medium with a continuously varying conductivity     

Shogo Kozaki 《Pure and Applied Geophysics》1976,114(6):879-889

Fields due to an electric current source in the atmosphere where the conductivity increases exponentially with altitude have been calculated. Characteristics of the field are described. The current source is assumednot to vary with time.Department of Electronic Engineering, Gumma University.  相似文献