Swell-dominant surface waves observed by a moored buoy with a GPS wave sensor in Otsuchi Bay,a ria in Sanriku,Japan     

Kosei Komatsu  Kiyoshi Tanaka 《Journal of Oceanography》2017,73(1):87-101

Real-time monitoring of wind and surface waves in Otsuchi Bay, Iwate, Tohoku, Japan, commenced in October 2012, using a mooring buoy with an ultrasonic anemometer and a single-mode GPS wave sensor. Wind and wave data are distributed hourly in real time via the Internet along with a chart of their time series. We analyzed data monitored in the first 3 months in order to assess the variability and occurrence of wind and waves and to elucidate the main reasons for wave variation in Otsuchi Bay. The monitoring data revealed that surface waves in the bay were predominantly affected by swells propagated from the northeastern offshore region and that the wave height was significantly correlated with the component of wind velocity toward Otsuchi Bay in the northeastern offshore region that faces the bay mouth. The offshore wind field was expected to provide information useful for predicting coastal waves in a ria bay in Sanriku such as Otsuchi Bay. However, it should be emphasized that the horizontal distribution of the offshore wind field which has a significant effect on the surface waves in a ria bay depends heavily on the topographic shape of the bay.  相似文献   

Paleolakes, paleofloods, and depressions in Aurorae and Ophir Plana, Mars: Connectivity of surface and subsurface hydrological systems     

Goro Komatsu  Gaetano Di Achille  Ciprian Popa  Stefano Di Lorenzo  Jose Alexis Palmero Rodriguez 《Icarus》2009,201(2):474-491

The plains of Aurorae and Ophir in the equatorial region of Mars display geomorphic evidence indicative of extensive but generally short-lived paleohydrological processes. Elaver Vallis in Aurorae Planum south of Ganges Chasma is an outflow channel system >180 km long, and here inferred to have formed by cataclysmic spillover flooding from a paleolake(s) contained in the Morella crater basin. Ganges Cavus is an enormous 5-km-deep depression of probable collapse origin located in the Morella basin. The fluid responsible for the infilling of the Morella basin likely emerged at least partially through Ganges Cavus or its incipient depression, and it may have been supplied also from small-scale springs in the basin. Similar paleohydrological processes are inferred also in Ophir Planum. It is reasonable to assume that water, sometimes sediment-laden and/or mixed with gases, was the responsible fluid for these phenomena although some of the observed features could be explained by non-aqueous processes such as volcanism. Water emergence may have occurred as consequences of ground ice melting or breaching of cryosphere to release water from the underlying hydrosphere. Dike intrusion is considered to be an important cause of formation for the cavi and smaller depressions in Aurorae and Ophir Plana, explaining also melting of ground ice or breaching of cryosphere. Alternatively, the depressions and crater basins may have been filled by regional groundwater table rising during the period(s) when cryosphere was absent or considerably thin. The large quantities of water necessary for explaining the paleohydrological processes in Aurorae and Ophir Plana could have been derived through crustal migration from the crust of higher plains in western Ophir Planum where water existed in confined aquifers or was produced by melting of ground ice due to magmatic heating or climatic shift, or from a paleolake in Candor Chasma further west.  相似文献   

GRS evidence and the possibility of paleooceans on Mars     

James M. Dohm  Victor R. Baker  William V. Boynton  Alberto G. Fairén  Justin C. Ferris  Michael Finch  Roberto Furfaro  Trent M. Hare  Daniel M. Janes  Jeffrey S. Kargel  Suniti Karunatillake  John Keller  Kris Kerry  Kyeong J. Kim  Goro Komatsu  William C. Mahaney  Dirk Schulze-Makuch  Lucia Marinangeli  Gian G. Ori  Javier Ruiz  Shawn J. Wheelock 《Planetary and Space Science》2009,57(5-6):664-684

The Gamma Ray Spectrometer (Mars Odyssey spacecraft) has revealed elemental distributions of potassium (K), thorium (Th), and iron (Fe) on Mars that require fractionation of K (and possibly Th and Fe) consistent with aqueous activity. This includes weathering, evolution of soils, and transport, sorting, and deposition, as well as with the location of first-order geomorphological demarcations identified as possible paleoocean boundaries. The element abundances occur in patterns consistent with weathering in situ and possible presence of relict or exhumed paleosols, deposition of weathered materials (salts and clastic minerals), and weathering/transport under neutral to acidic brines. The abundances are explained by hydrogeology consistent with the possibly overlapping alternatives of paleooceans and/or heterogeneous rock compositions from diverse provenances (e.g., differing igneous compositions).  相似文献   

Relationship between canopy height and the reference value of surface conductance for closed coniferous stands     

Hikaru Komatsu 《水文研究》2003,17(12):2503-2512

When estimating the dry‐canopy evaporation rate of coniferous stands using the Penman–Monteith equation, it is crucial to determine the reference value of surface conductance G_s. This paper examines the relationship between canopy height and the reference value of G_s based on the maximum value of G_s with a vapour pressure deficit ≥ 1·0 kPa, ?_{s max}. There is a clear correlation between canopy height and ?_{s max} when the projected leaf area index ≥3·0. This suggests that using this relationship will enable more accurate determination of the reference value of G_s for closed stands. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Geological features indicative of processes related to the hematite formation in Meridiani Planum and Aram Chaos, Mars: a comparison with diagenetic hematite deposits in southern Utah, USA     

Jens Ormö  Goro Komatsu  Brenda Beitler 《Icarus》2004,171(2):295-316

In order to understand the formation of the few but large, hematite deposits on Mars, comparisons are often made with terrestrial hematite occurrences. In southern Utah, hematite concretions have formed within continental sandstones and are exposed as extensive weathered-out beds. The hematite deposits are linked to geological and geomorphological features such as knobs, buttes, bleached beds, fractures and rings. These terrestrial features are visible in aerial and satellite images, which enables a comparison with similar features occurring extensively in the martian hematite-rich areas. The combination of processes involved in the movement and precipitation of iron in southern Utah can provide new insights in the context of the hematite formation on Mars. Here we present a mapping of the analogue geological and geomorphological features in parts of Meridiani Planum and Aram Chaos. Based on mapping comparisons with the Utah occurrences, we present models for the formation of the martian analogues, as well as a model for iron transport and precipitation on Mars. Following the Utah model, high albedo layers and rings in the mapped area on Mars are due to removal or lack of iron, and precipitation of secondary diagenetic minerals as fluids moved up along fractures and permeable materials. Hematite was precipitated intraformationally where the fluid transporting the reduced iron met oxidizing conditions. Our study shows that certain geological/geomorphological features can be linked to the hematite formation on Mars and that pH differences could suffice for the transport of the iron from an orthopyroxene volcanoclastic source rock. The presence of organic compounds can enhance the iron mobilization and precipitation processes. Continued studies will focus on possible influence of biological activity and/or methane in the formation of the hematite concretions in Utah and on Mars.  相似文献   

Three-dimensional mapping of red stingray (Dasyatis akajei) movement with reference to bottom topography     

Otaki  Takayoshi  Hamana  Masahiro  Tanoe  Hideaki  Miyazaki  Nobuyuki  Shibuno  Takuro  Komatsu  Teruhisa 《Ocean Science Journal》2015,50(2):327-334

Most demersal fishes maintain strong relations with bottom substrates and bottom depths and/or topography during their lives. It is important to know these relations to for understand their lives. In Tokyo Bay, red stingray, Dasyatis akajei, classified as near-threatened species by IUCN, has increased since the 1980s. It is a top predator and engages in ecosystem engineer by mixing the sand bed surface through burring behavior, and greatly influences a coastal ecosystem. It is reported that this species invades in plage and tidal flats and has sometimes injured beachgoers and people gathering clams in Tokyo bay. Thus, it is necessary to know its behavior and habitat use to avoid accidents and to better conserve the biodiversity of ecosystems. However, previous studies have not examined its relationship with the bottom environment. This study aims to describe its behavior in relation to the bottom environment. We sounded three dimensional bottom topography of their habitat off Kaneda Cove in Tokyo Bay with interferometric sidescan sonar system and traced the movement of red stingrays by attaching a data logger system to survey their migration. The results revealed that red stingray repeated vertical movement between the surface and bottom, and used not only sand beds but also rocky beds.

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A three-dimensional numerical model of hydrodynamics and water quality in Hakata Bay   总被引：1，自引：0，他引：1  

Yongming Shen  Yonghong Zheng  Toshimitsu Komatsu  Naoko Kohashi 《Ocean Engineering》2002,29(4):461-473

The hydrodynamics and water quality in Hakata Bay, Japan, are strongly affected by the seasonal variations in both the gravitational circulation and the stratification in the bay. The three-dimensional hydrodynamics and water quality model has been developed to simulate the long-term transport and fate of pollutants in the system. The model is unique in that it completely integrates the refined modelling of the hydrodynamics, biochemical reactions and the ecosystem in the coastal areas. It is a 3-dimensional segmented model which is capable of resolving mean daily variations in all the parameters relevant to pollution control. It predicts daily fluctuations in the oxygen content at different depths in water throughout the year. It takes into account transport and settling of pollutant particles. It predicts light penetration from computed turbidity variations. It includes interactions between the ecosystem and water quality, through nutrient cycling and photosynthesis. The model has been calibrated well against the data set of historical water quality observations in Hakata Bay.  相似文献   

Temporal fluctuations of water temperature in aSargassum forest     

Teruhisa Komatsu 《Journal of Oceanography》1985,41(4):235-243

This paper examines the influence of aSargassum forest on temporal fluctuations in temperatures of surrounding water in relation to the thermal structure of water in and above theSargassum forest. Water temperature records were obtained at about one-minute intervals for almost two days in May 1977 during the season of luxuriant seaweed growth, and in August 1977 during the season of little growth. The fluctuations were divided into two types. (1) A diurnal fluctuation under the forest with about a three hour lag behind that above the forest during the season of luxuriant growth but with about a 30 min lag during the season of little growth. (2) Sharp spike-like fluctuations with periods shorter than five minutes appearing only in the dense canopy or floating seaweeds in the surface and subsurface layers during the period of luxuriant growth. The luxuriant forest ofSargassum seems to influence the spatial distribution of water temperature and consequently seems to induce the fluctuations mentioned above. The relationship between short period fluctuations and behaviours of larval fishes are discussed.  相似文献   

Origin of glacial–fluvial landforms in the Azas Plateau volcanic field, the Tuva Republic, Russia: Role of ice–magma interaction     

Goro Komatsu  Sergei G. Arzhannikov  Anastasia V. Arzhannikova  Gian Gabriele Ori 《Geomorphology》2007,88(3-4):352-366

The basaltic Azas Plateau volcanic field is located in the Tuva Republic of the Russian Federation. The area was glaciated multiple times, and the field is characterized by the formation of subglacial volcanoes called tuyas, but subaerial volcanoes and lava fields also exist. A combined study of remote sensing and field observations in the vicinity of the tuyas in the southeastern Azas Plateau volcanic field identified landforms that are best explained by the jökulhlaup hypothesis. The landforms include elongated hills, paleochannels, and butte and basin topography. These landforms are hypothesized to have formed by both erosion and deposition caused by high-energy water streams. The triggering for the hypothesized jökulhlaups was either melting of ice by subglacial volcanism and/or destabilization of ice-dammed/subglacial reservoirs. The age estimation of the flood events is difficult, but they probably occurred during the ice ages of the Quaternary, as late as in the Middle-Late Pleistocene.  相似文献   

Geochemical Features of Vein Anhydrite from the Kakkonda Geothermal System, Northeast Japan     

Munetake Sasaki    Koichiro Fujimoto    Hitoshi Tsukamoto    Takayuki Sawaki    Masakatsu Sasada    Masanori Kurosawa  Masahiko Yagi    Yoichi Muramatsu    Osamu Kato  +  Ryo Komatsu  +  Kaichiro Kasai  + Nobuo Doi+ 《Resource Geology》2003,53(2):127-142

Abstract. Cathodoluminescence (CL) color, rare earth element (REE) content, sulfur and oxygen isotopes and fluid inclusions of anhydrite, which frequently filled in hydrothermal veins in the Kakkonda geothermal system, were investigated to elucidate the spatial, temporal and genetical evolution of fluids in the deep reservoir. The anhydrite samples studied are classified into four types based on CL colors and REE contents: type-N (no color), type-G (green color), type-T (tan color) and type-S (tan color with a high REE content). In the shallow reservoir, only type-N anhydrite is observed. In the deep reservoir, type-G anhydrite occurs in vertical veins whereas type-T and -N in lateral veins. Type-S anhydrite occurs in the heat-source Kakkonda Granite. The CL textures revealed that type-G anhydrite deposited earlier than type-T in the deep reservoir, implying that fracture system was changed from predominantly vertical to lateral.
Studies of fluid inclusions and δ³⁴S and δ¹⁸O values of the samples indicate that type-N anhydrite deposited from diluted fluids derived from meteoric water, whereas type-G, -T and -S anhydrites deposited from magmatic brines derived from the Kakkonda Granite with the exception of some of type-G with recrystallization texture and no primary fluid inclusion, which deposited from fossil seawater preserved in the sedimentary rocks. Type-G, -T and -S anhydrites exhibit remarkably different chondrite-normalized REE patterns with a positive Eu anomaly, with a convex shape (peak at Sm or Eu) and with a negative Eu anomaly, respectively. The difference in the patterns might result from the different extent of hydrothermal alteration of the reservoir rocks and contribution of the magmatic fluids.  相似文献