Internal gravity wave selection in the upper troposphere and lower stratosphere observed by the MU radar: Preliminary results     

Manabu D. Yamanaka  Shoichiro Fukao  Hiromasa Matsumoto  Toru Sato  Toshitaka Tsuda  Susumu Kato 《Pure and Applied Geophysics》1989,130(2-3):481-495

Marked wavelike variations of the lower stratospheric wind observed on 7–10 May, 1985 by an MST radar in Japan (by the MU radar) are analyzed assuming that they are induced by monochromatic internal inertio-gravity waves. These variations are mainly composed of two modes (periods: 22 and 24 hours), both of which have zonal phase velocities (C _X ) slower than the mean westerly wind (). A statistical analysis of the zonal phase velocity shows thatC _X above andC _X below the tropopause jet stream, which is considered to be a vivid proof of wave selection due to the tropospheric mean flow and upward wave emission from the tropopause jet. A comparison between the MU radar results and routine meteorological observations leads to the conclusion that the marked waves appear when the jet stream takes a maximum wind speed.  相似文献   

Determination of the role of entrapped air in water flow in a closed soil pipe using a laboratory experiment          下载免费PDF全文

Takuhei Yamasaki  Hiromi Imoto  Shoichiro Hamamoto  Taku Nishimura 《水文研究》2017,31(21):3740-3749

Soil pipes, continuous macropores parallel to the soil surface, are an important factor in hillslope hydrological processes. However, the water flow dynamics in soil pipes, especially closed soil pipes, are not well understood. In this study, the water and air dynamics within closed soil pipes have been investigated in a bench‐scale laboratory experiment by using a soil box with an artificial acrylic soil pipe. In order to grasp the state of water and air within the soil pipe, we directly measured the existing soil pipe flow and air pressure in the soil pipe. The laboratory experiment showed that air in the soil pipe had an important role in the water flow in the closed soil pipe. When air entrapment occurred in the soil pipe before the soil matrix around the soil pipe was saturated with water, water intrusion in the soil pipe was prevented by air entrapped in the pipe, which inhibited the soil pipe flow. This air entrapment in the soil pipe was controlled by the soil water and air flow. Moreover, after the soil pipe flow started, the soil pipe was not filled completely with water even when the soil pipe was completely submerged under the groundwater table. The entrapped air in the soil pipe prevented further water intrusion in the soil pipe.  相似文献   

Effects of disturbance of seawater excited by internal wave on GNSS-acoustic positioning     

Matsui  R.  Kido  M.  Niwa  Y.  Honsho  C. 《Marine Geophysical Researches》2019,40(4):541-555

Traditional Global Navigation Satellite System-Acoustic (GNSS-A) positioning assumes the Layered Model in the sound speed structure, and any of horizontal perturbation of seawater degrades its accuracy. However, the use of the Gradient Model analytically demonstrated that the horizontal gradient of the sound speed structure and displacement can simultaneously be solved using multiple transponders for each of ping. We applied this technique to our observed data and found it unsuitable for real data. We confirmed that a horizontal perturbation with wavelength shorter than the horizontal extent of the transponder array significantly violates the linear approximation in the Gradient Model. Our vertical 2D numerical simulation of internal waves (IWs) forced by tidal oscillation showed that such small-scale IWs could effectively be generated by nonlinear cascade from large-scale IWs of the major tidal constituents. In addition, a small-scale IW in deep water typically has a period of 3–4 h, which degrades positioning accuracy significantly, whereas an IW of much shorter period in shallow water has less effect after removal of the fluctuation by time averaging within a typical observation period. Apparent array position obtained in the synthetic test based on the simulated IW-derived sound speed structure showed features quite similar to that observed in real surveys. To incorporate such deeper perturbation, we proposed a Disturbance Model using dual sea surface platforms, that can solve time-varying perturbation in the vicinity of each transponder.

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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   

Demonstration of crystalline forsterite grain formation due to coalescence growth of Mg and SiO smoke particles     

C. Kaito  Y. Ojima  K. Kamitsuji  O. Kido  Y. Kimura  H. Suzuki  T. Sato  T. Nakada  Y. Saito  C. Koike 《Meteoritics & planetary science》2003,38(1):49-57

Abstract— Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain‐grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg₂Si polyhedral grains were obtained in a Mg grain‐rich atmosphere. Mg₂SiO₄ polyhedral grains were obtained in a SiO grain‐rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite.  相似文献   

Influence of plasma on formation of crystalline Fe₂SiO₄ grains     

T. Sato  M. Kurumada  O. Kido  M. Shintaku  Y. Saito 《Planetary and Space Science》2006,54(6):612-616

The production of Fe₂SiO₄ (fayalite) crystalline grains was performed by two processes, namely, grain formation in a plasma field by evaporating a mixture powder of Fe and SiO and heat treatment of the product collected on the radio-frequency (RF) electrode side. Fe grains <20 nm in size covered with an amorphous SiO layer selectively formed Fe₂SiO₄ grains by heating at 800 °C. By heating at 600 °C, in addition to the formation of Fe₂SiO₄ crystal grains, the FeO phase appeared. The doping effect of excited oxygen in a plasma field into the Fe small grains may be the trigger on the formation of fayalite through the FeO phase formation. The present experimental result suggests that the probability of Fe₂SiO₄ grain formation in space is low.  相似文献   

JCOPE-FGO: an eddy-resolving quasi-global ocean reanalysis product     

Kido  Shoichiro  Nonaka  Masami  Miyazawa  Yasumasa 《Ocean Dynamics》2022,72(8):599-619

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Relationship between trace elements and depositional environments in shallow sediments: a case study from Southern Kanto Plain,Central Japan     

Masato Ueshima  Takato Takemura  Takeshi Saito  Yoshiharu Ito  Shoichiro Hamamoto  Hirotaka Saito  Toshiko Komatsu 《Environmental Earth Sciences》2017,76(18):633

Underground developments such as subways and shopping facilities have been increasing in number and magnitude in the relatively shallow subsurface of many urban areas where the earth materials commonly are composed of marine sediments. Marine sediments can contain significant amounts of toxic trace elements such as arsenic, boron, and lead. Changes in the subsurface environment caused by excavation and construction in underground developments could potentially cause these toxic elements to be dissolved into pore water of the sediments, which might lead to groundwater pollution. The purpose of this study is to investigate correlations among chemical properties of marine sediments, such as pH and electrical conductivity (EC), concentrations of toxic trace elements, and stratigraphic characteristics of the sediments. We selected three sites with different stratigraphic settings in the southern Kanto Plain around the Tokyo Metropolis. We collected core samples from shallow strata at a site in the Arakawa Lowland, southern Saitama, and at two sites in the Musashino Upland, Middle Tokyo. All sites have both marine and non-marine sediments up to 50–60 m in thickness. We determined trace element concentrations in the pore water, pH, EC, and loss on ignition. The results show that (1) the marine sediments tend to have low pH, high EC, and high sulfur concentration compared to the non-marine sediments (2) the concentration of most of the soluble heavy metals vary depending on the concentration of sulfate, the pH, and the formation processes of the strata, (3) the arsenic concentration is not related to sulfur concentration but apparently to Fe and Al concentrations, (4) the boron concentration is not related to any other properties implying that the boron level is independent of and cannot be predicted by common chemical properties, and (5) for all three sites, concentrations of most of the trace elements, EC, pH, and sulfate concentration were correlated with each other. This study shows that the concentration and potential mobilization of many toxic trace elements in marine sediments could be predicted by easily measurable pore water chemical properties such as pH and EC. This could be useful for predicting and avoiding the risk of groundwater pollution during underground development projects.  相似文献   

Morphological transitions for pore water and pore air during drying and wetting processes in partially saturated sand     

Kido  Ryunosuke  Higo  Yosuke  Takamura  Fukushi  Morishita  Ryoichi  Khaddour  Ghonwa  Salager  Simon 《Acta Geotechnica》2020,15(7):1745-1761

Acta Geotechnica - Water retention characteristics are important for modeling the mechanical and hydraulic behavior of partially saturated sand. It is well known that the soil water characteristic...  相似文献   

Microscopic characteristics of partially saturated dense sand and their link to macroscopic responses under triaxial compression conditions     

Kido  Ryunosuke  Higo  Yosuke 《Acta Geotechnica》2020,15(11):3055-3073

Acta Geotechnica - This paper presents a set of triaxial compression tests on partially saturated dense sands to clarify the microscopic characteristics and their link to the macroscopic responses....  相似文献