Effect of bedrock flow on catchment rainfall‐runoff characteristics and the water balance in forested catchments in Tanzawa Mountains,Japan     

Tomoki Oda  Masakazu Suzuki  Tomohiro Egusa  Yoshimi Uchiyama 《水文研究》2013,27(26):3864-3872

In this paper, we examined the role of bedrock groundwater discharge and recharge on the water balance and runoff characteristics in forested headwater catchments. Using rigorous observations of catchment precipitation, discharge and streamwater chemistry, we quantified net bedrock flow rates and contributions to streamwater runoff and the water balance in three forested catchments (second‐order to third‐order catchments) underlain by uniform bedrock in Japan. We found that annual rainfall in 2010 was 3130 mm. In the same period, annual discharge in the three catchments varied from 1800 to 3900 mm/year. Annual net bedrock flow rates estimated by the chloride mass balance method at each catchment ranged from ?1600 to 700 mm/year. The net bedrock flow rates were substantially different in the second‐order and third‐order catchments. During baseflow, discharge from the three catchments was significantly different; conversely, peak flows during large storm events and direct runoff ratios were not significantly different. These results suggest that differences in baseflow discharge rates, which are affected by bedrock flow and intercatchment groundwater transfer, result in the differences in water balance among the catchments. This study also suggests that in these second‐order to third‐order catchments, the drainage area during baseflow varies because of differences between the bedrock drainage area and surface drainage area, but that the effective drainage area during storm flow approaches the surface drainage area. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Noble gases in enstatite chondrites released by stepped crushing and heating     

Ryuji OKAZAKI  Nobuo TAKAOKA  Keisuke NAGAO  Tomoki NAKAMURA 《Meteoritics & planetary science》2010,45(3):339-360

Abstract– Enstatite chondrites (ECs) were subjected to noble gas analyses using stepped crushing and pyrolysis extraction methods. ECs can be classified into subsolar gas‐carrying and subsolar gas‐free ECs based on the ³⁶Ar/⁸⁴Kr/¹³²Xe ratios. For subsolar gas‐free ECs, elemental ratios, and Xe isotopic compositions indicate that Q gas is the dominant trapped component, the Q gas concentration can be correlated with the petrologic type, reasonably explained by gas release from a common EC parental material during subsequent heating. Atmospheric Xe with sub‐Q elemental ratios is found in Antarctic E3s at 600–800 °C and through crushing. The ¹³²Xe released in these fractions accounts for 30–60% of the bulk concentrations. Hence, the sub‐Q signature is generally due to contamination of elementally fractionated atmosphere. Subsolar gas is mainly released (up to 78% of the bulk ³⁶Ar) at 1300–1600 °C and through crushing, suggesting that enstatite and friable phases are the host phases. Subsolar gas is isotopically identical to solar gas, but elementally fractionated. These observations are consistent with a previous study, which suggested that subsolar gas could be fractionated solar wind having been implanted into chondrule precursors ( Okazaki et al. 2001 ). Unlike subsolar gas‐free ECs, the primordial gas concentrations of subsolar gas‐carrying ECs are not simply correlated with the petrologic type. It is inferred that subsolar gas‐rich chondrules were heterogeneously distributed in the solar nebula and accreted to form subsolar gas‐carrying ECs. Subsequent metamorphic and impact‐shock heating events have affected noble gas compositions to various degrees.  相似文献   

Suspended sediment discharge in subsurface flow from the head hollow of a small forested watershed,northern Japan     

Tomomi Terajima  Tomoki Sakamoto  Yuichiro Nakai  Kenzo Kitamura 《地球表面变化过程与地形》1997,22(11):987-1000

Surface flow and suspended sediment discharge from the head hollow of the Jozankei Experimental Watershed in Hokkaido, northern Japan, were measured to clarify the implications of subsurface hydrology for soil movement. Subsurface discharges during the extremely large storms of 1993 to 1994 were measured in a V-notch weir installed at a natural spring near the bottom of the head hollow, and shallow groundwater levels were observed in the wells excavated in the hollow. Sediment samples whose particle size range from 0·001 to 0·1 mm were manually and automatically collected at 15 to 60 min intervals, by use of 1 or 21 polyethylene bottles. Maximum concentration and flux of suspended sediment during the storms preceded the peak discharge of subsurface flow by several hours. Neither the changes in concentration (mg l⁻¹) nor flux (mg s⁻¹) of suspended sediment coincided with those in subsurface discharge (l s⁻¹). Furthermore, sediment concentration was poorly correlated with the rate of change in subsurface discharge (l s⁻²) during the rising limb of the hydrograph. Suspended sediment flux during the acceleratory limb, however, was closely correlated with the rate of change in subsurface discharge. The relationship between suspended sediment flux and rate of change in subsurface discharge were in inverse proportion to initial subsurface discharge before the storm runoff and they represented rare seasonal variation. Subsurface hydraulic erosion and transport of suspended sediment resulting from changes in rate of change in subsurface discharge actively occur during the acceleratory rising limb of the hydrograph. Accordingly, subsurface hydraulic erosion during the acceleratory rising limb of the hydrograph can be physically understood by analysing suspended sediment flux associated with rate of change in subsurface discharge and initial subsurface discharge. © 1997 John Wiley & Sons, Ltd.  相似文献   

Energy balance above a boreal coniferous forest: a difference in turbulent fluxes between snow‐covered and snow‐free canopies     

Yuichiro Nakai  Tomoki Sakamoto  Tomomi Terajima  Kenzo Kitamura  Tomoki Shirai 《水文研究》1999,13(4):515-529

To evaluate the interactive effects of snow and forest on turbulent fluxes between the forest surface and the atmosphere, the surface energy balance above a forest was measured by the eddy correlation method during the winter of 1995–1996. The forest was a young coniferous plantation comprised of spruce and fir. The study site, in Sapporo, northern Japan, had heavy and frequent snowfalls and the canopy was frequently covered with snow during the study period. A comparison of the observed energy balance above the forest for periods with and without a snow‐covered canopy and an analysis using a single‐source model gave the following results: during daytime when the canopy was covered with snow, the upward latent heat flux was large, about 80% of the net radiation, and the sensible heat flux was positive but small. On the other hand, during daytime when the canopy was dry and free from snow, the sensible heat flux was dominant and the latent heat flux was minor, about 10% of the net radiation. To explain this difference of energy partition between snow‐covered and snow‐free conditions, not only differences in temperature but also differences in the bulk transfer coefficients for latent heat flux were necessary in the model. Therefore, the high evaporation rate from the snow‐covered canopy can be attributed largely to the high moisture availability of the canopy surface. Evaporation from the forest during a 60‐day period in midwinter was estimated on a daily basis as net radiation minus sensible heat flux. The overall average evaporation during the 60‐day period was 0·6 mm day⁻¹, which is larger than that from open snow fields. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Combining IR and X‐ray microtomography data sets: Application to Itokawa particles and to Paris meteorite     

Zelia Dionnet  Rosario Brunetto  Alice Alon‐Toppani  Stefano Rubino  Donia Baklouti  Ferenc Borondics  Anne‐Ccile Buellet  Zahia Djouadi  Andrew King  Tomoki Nakamura  Alessandra Rotundi  Christophe Sandt  David Troadec  Akira Tsuchiyama 《Meteoritics & planetary science》2020,55(7):1645-1664

In the near future, a new generation of sample return missions (Hayabusa2, OSIRIS‐REx, MMX, etc.) will collect samples from small solar system bodies. To maximize the scientific outcome of laboratory studies and minimize the loss of precious extraterrestrial samples, an analytical sequence from less destructive to more destructive techniques needs to be established. In this work, we present a combined X‐ray and IR microtomography applied to five Itokawa particles and one fragment of the primitive carbonaceous chondrite Paris. We show that this analytical approach is able to provide a 3‐D physical and chemical characterization of individual extraterrestrial particles, using the measurement of their 3‐D structure and porosity, and the detection of mineral and organic phases, and their spatial co‐localization in 3‐D. We propose these techniques as an efficient first step in a multitechnique analytical sequence on microscopic samples collected by space missions.  相似文献   

Visualising Crime Clusters in a Space‐time Cube: An Exploratory Data‐analysis Approach Using Space‐time Kernel Density Estimation and Scan Statistics     

Tomoki Nakaya  Keiji Yano 《Transactions in GIS》2010,14(3):223-239

For an effective interpretation of spatio‐temporal patterns of crime clusters/hotspots, we explore the possibility of three‐dimensional mapping of crime events in a space‐time cube with the aid of space‐time variants of kernel density estimation and scan statistics. Using the crime occurrence dataset of snatch‐and‐run offences in Kyoto City from 2003 to 2004, we confirm that the proposed methodology enables simultaneous visualisation of the geographical extent and duration of crime clusters, by which stable and transient space‐time crime clusters can be intuitively differentiated. Also, the combined use of the two statistical techniques revealed temporal inter‐cluster associations showing that transient clusters alternatively appeared in a pair of hotspot regions, suggesting a new type of “displacement” phenomenon of crime. Highlighting the complementary aspects of the two space‐time statistical approaches, we conclude that combining these approaches in a space‐time cube display is particularly valuable for a spatio‐temporal exploratory data analysis of clusters to extract new knowledge of crime epidemiology from a data set of space‐time crime events.  相似文献   

Mineralogical alteration of a type A CAI from Allende CV3 chondrite: Formation of secondary dmisteinbergite and its phase transition to anorthite     

Yuma Enokido  Tomoki Nakamura  Megumi Matsumoto  Akira Miyake  Takazo Shibuya  Changkun Park  Mike Zolensky 《Meteoritics & planetary science》2023,58(3):405-420

Dmisteinbergite, a hexagonal form of CaAl₂Si₂O₈, was found in a compact type A Ca-Al-rich inclusion (CAI) in the Allende CV3 chondrite. Scanning and transmission electron microscopic observations show that dmisteinbergite was always in contact with grossular and grossular was in contact with melilite. In addition, there is a crystallographic relationship between dmisteinbergite and anorthite. Based on the textural and crystallographic evidence, the following mineralogical alteration processes are proposed to have occurred in the CAI. (1) Melilite was replaced by grossular. High densities of vesicles in the grossular indicate that hydrogrossular might have been the primary alteration phase and dehydrated by later metamorphism. (2) Dmisteinbergite formed from (hydro)grossular through a reaction with Si-rich fluid. (3) Nano-sized minerals are formed within dmisteinbergite. (4) Dmisteinbergite was transformed to anorthite. (5) Both anorthite and dmisteinbergite were altered to nepheline. (6) Hydrogrossular was dehydrated to grossular. (Hydro)grossular, dmisteinbergite, anorthite, and nepheline in the CAI seem to have formed in the course of metasomatism that occurred in the Allende parent body. Except for the hydrogrossular dehydration, these reactions could have occurred at moderate temperature (200–250°C) in high pH fluids (pH 13–14) according to past experimental studies. Episodic changes in fluid composition seem to have occurred before reactions (2), (4), and (5), because these reactions were not completed before the next reaction started. Higher temperature is required for reactions (5) and (6) to occur. Our observation of the CAI suggests that it experienced multiple episodes of metasomatism as temperatures were rising in the Allende parent asteroid.  相似文献   

On the Ningaloo Niño/Niña     

Takahito Kataoka  Tomoki Tozuka  Swadhin Behera  Toshio Yamagata 《Climate Dynamics》2014,43(5-6):1463-1482

Using both observational and reanalysis data, evolution processes of a regional climate phenomenon off Western Australia named recently “Ningaloo Niño (Niña)” are studied in detail. It is also shown that the Ningaloo Niño (Niña) has significant impacts on the precipitation over Australia. The Ningaloo Niño (Niña), which is associated with positive (negative) sea surface temperature (SST) anomalies and atmospheric anomalies off the western coast of Australia, peaks during austral summer and is classified into two types based on the difference in the evolution process. The first type called a locally amplified mode develops through an intrinsic unstable air–sea interaction off the western coast of Australia; an anomalous cyclone (anticyclone) generated by positive (negative) SST anomalies forces northerly (southerly) alongshore wind anomalies, which induce coastal downwelling (upwelling) anomalies, and enhance the positive (negative) SST anomalies further. The second type called a non-locally amplified mode is associated with coastally trapped waves originating in either the western tropical Pacific, mostly related to El Niño/Southern Oscillation, or the northern coast of Australia. Positive (negative) SST anomalies in both modes are associated with an anomalous low (high) off the western coast of Australia. The sea level pressure (SLP) anomalies in the locally amplified mode are regionally confined with a cell-like pattern and produce a sharp offshore pressure gradient along the western coast of Australia, whereas those in the non-locally amplified mode tend to show a zonally elongated pattern. The difference is found to be related to conditions of the continental SLP modulated by the Australian summer monsoon and/or the Southern Annular Mode.  相似文献   

Contribution of oceanic wave propagation from the tropical Pacific to asymmetry of the Ningaloo Niño/Niña     

Kusunoki  Hidehiro  Kido  Shoichiro  Tozuka  Tomoki 《Climate Dynamics》2020,54(11):4865-4875

Climate Dynamics - Ningaloo Niño/Niña is the dominant mode of interannual variability of sea surface temperature (SST) in the southeastern Indian Ocean. According to previous studies,...  相似文献   

Hayabusa‐returned sample curation in the Planetary Material Sample Curation Facility of JAXA     

Toru YADA  Akio FUJIMURA  Masanao ABE  Tomoki NAKAMURA  Takaaki NOGUCHI  Ryuji OKAZAKI  Keisuke NAGAO  Yukihiro ISHIBASHI  Kei SHIRAI  Michael E. ZOLENSKY  Scott SANDFORD  Tatsuaki OKADA  Masayuki UESUGI  Yuzuru KAROUJI  Maho OGAWA  Shogo YAKAME  Munetaka UENO  Toshifumi MUKAI  Makoto YOSHIKAWA  Junichiro KAWAGUCHI 《Meteoritics & planetary science》2014,49(2):135-153

Abstract– The Planetary Material Sample Curation Facility of JAXA (PMSCF/JAXA) was established in Sagamihara, Kanagawa, Japan, to curate planetary material samples returned from space in conditions of minimum terrestrial contaminants. The performances for the curation of Hayabusa‐returned samples had been checked with a series of comprehensive tests and rehearsals. After the Hayabusa spacecraft had accomplished a round‐trip flight to asteroid 25143 Itokawa and returned its reentry capsule to the Earth in June 2010, the reentry capsule was brought back to the PMSCF/JAXA and was put to a series of processes to extract recovered samples from Itokawa. The particles recovered from the sample catcher were analyzed by electron microscope, given their ID, grouped into four categories, and preserved in dimples on quartz slide glasses. Some fraction of them has been distributed for initial analyses at NASA, and will be distributed for international announcement of opportunity (AO), but a certain fraction of them will be preserved in vacuum for future analyses.  相似文献