Eddy Field in the Japan Sea Derived from Satellite Altimetric Data   总被引：2，自引：0，他引：2  

Akihiko Morimoto  Tetsuo Yanagi  Akio Kaneko 《Journal of Oceanography》2000,56(4):449-462

The Japan Sea is one of the eddy-rich areas in the world. Many researchers have described the variability of the eddy field and its structure in the Tsushima Warm Current region. On the other hand, since there are few data covering the northern part of the Japan Sea, we are not able to understand the detailed variability of the eddy field there. The variation of the eddy field in the Japan Sea is investigated using the temporal fluctuations of sea surface height measured by altimetric data from TOPEX/POSEIDON and ERS-2. Tidal signals are eliminated from the altimetric data on the basis of the results of Morimoto et al. (2000). Distributions of sea surface dynamic height are produced by using the optimal interpolation method every month. The distributions warm and cold eddies that we obtained coincide well with the observed isotherms at 100 m depth measured by the Japan Sea National Fisheries Research Institute and the sea surface temperature measured by satellite. There are areas with high RMS variability of temporal fluctuation of sea surface dynamic height in the Yamato Basin, the Ulleung Basin, east of North Korea, the eastern part of the Yamato Rise, the Tsushima Strait and west of Hokkaido. The characteristics of eddy propagation in the high RMS variability regions are examined using a lag correlation analysis. Seasonal variations in the number of warm and cold eddies are also examined.  相似文献   

Detection of detached dust envelopes around oxygen-rich AGB stars     

O. Hashimoto  H. Izumiura  D. J. M. Kester  Tj. R. Bontekoe 《Astrophysics and Space Science》1995,224(1-2):477-478

Extended emission components are clearly found in the IRAS scan data of optically visible oxygen-rich AGB stars which show no 10µm silicate band feature in the IRAS LRS spectra but a strong infrared excess in the IRAS photometric data. It is most likely that these stars really have their circumstellar dust envelopes, which are detached from the central stars, indicating a halting of mass loss for a significant period.  相似文献   

Isophot Mapping Observations of Carbon Stars     

H. Izumiura  O. Hashimoto 《Astrophysics and Space Science》1997,255(1-2):341-347

Mapping observations have been made toward five carbon stars in the far-infrared using ISOPHOT, an imaging photo-polarimeter on board the Infrared Space Observatory. Cold, very extended dust shells are clearly revealed in two of them. Y CVn is surrounded by a very extended, detached dust shell, which indicates a sudden decline of the mass-loss by two orders of magnitude in the last (1-2) × 104 years on a short time scale. The Hipparcos parallax reinforces our previous conclusion that Y CVn is a J-type carbon star on the asymptotic giant branch. U Ant shows a double shell structure, a compact dust shell surrounded by a very extended one. The outer shell has a brightness comparable to the dust shell of Y CVn. The structure indicates that there were two different high mass-loss phases separated by a period with a much lower mass-loss rate in between the two. The structure is consistent with the double dust shell proposed for this star by Izumiura et al. (1997) based on a detailed investigation of IRAS survey data. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Molecular distribution in the comae of H2O-comets: An analytic model     

Tetsuo Yamamoto 《Earth, Moon, and Planets》1981,24(2):175-188

Density distribution in cometary comae resulting from photodissociation, ionization and ion-molecule reaction of H₂O is investigated in an analytic manner. It is assumed that particles expand isotropically around the nucleus, and that each species has its own constant radial velocity. Formulae for the density distribution of photochemical products are presented throught the coma, and approximate formulae are given for the distribution of ion-molecule reaction products in the inner coma. Characterictics of the density profile are discussed on the basis of these analytic formulae.  相似文献   

On the photochemical formation of CN,C2, and C3 radicals in cometary comae     

Tetsuo Yamamoto 《Earth, Moon, and Planets》1981,24(4):453-463

The formation of cometary CN, C₂ and C₃ radicals is investigated in a photochemical reaction scheme. From an analysis of the observed brightness profiles of these radicals, it is shown that CN is formed as a primary product in the photolysis of its parent molecules, whereas C₂ and C₃ are formed via two-step photodissociation of their parents. We suggest that major parent of C₂ is different species from those of CN and C₃ on the basis of the difference of the variation with heliocentric distance of the sublimation rate of the parents of these radicals. Parent molecules and reaction schemes for the formation of these radicals are discussed.  相似文献   

Correction to: Mapping method of rainfall-induced landslide hazards by infiltration and slope stability analysis     

Dolojan  Nilo Lemuel J.  Moriguchi  Shuji  Hashimoto  Masakazu  Terada  Kenjiro 《Landslides》2021,18(6):2059-2059

Landslides - A Correction to this paper has been published: https://doi.org/10.1007/s10346-021-01642-4  相似文献   

A large hydrothermal reservoir beneath Taal Volcano (Philippines) revealed by magnetotelluric resistivity survey: 2D resistivity modeling     

Y. Yamaya  P. K. B. Alanis  A. Takeuchi  J. M. Cordon Jr.  T. Mogi  T. Hashimoto  Y. Sasai  T. Nagao 《Bulletin of Volcanology》2013,75(7):1-13

Taal Volcano, located in the southwestern part of Luzon Island, Philippines, has frequently experienced catastrophic eruptions from both the Main Crater on Volcano Island and flank eruptions. These eruptions have been magmatic, phreatomagmatic, and hydrothermal, with the latter implying the existence of a large-scale hydrothermal system beneath the volcano. We conducted an electrical resistivity survey using the magnetotelluric method in order to identify the location and geometry of the hydrothermal reservoir and sealing cap rock. Two-dimensional inversion using the observed data indicates four similar resistivity sections. The structure at shallow depths corresponds to volcanic deposits and an aquifer. Below 1 km, the structure features a relatively resistive zone beneath the main crater surrounded by a conductive shell. We interpreted these to be a large hydrothermal reservoir with an impermeable cap rock sealing it. Recent ground deformation detected by GPS measurements suggests that the hydrothermal reservoir is active. The interpreted cap rock thins just beneath the main crater and could easily be destroyed by an imbalance in the hydrothermal system. We conclude that this hydrothermal reservoir plays a significant role in driving catastrophic eruptions that begin with a hydrothermal explosion at the main crater.  相似文献   

Solidification depth and crystallization age of the Shiaidani Granodiorite: Constraints to the average denudation rate of the Hida Range,central Japan     

Tetsuo Kawakami  Shigeru Sueoka  Tatsunori Yokoyama  Saya Kagami  Georgina E. King  Frédéric Herman  Sumiko Tsukamoto  Takahiro Tagami 《Island Arc》2021,30(1):e12414

Solidification pressure and crystallization age of the ~5 Ma Shiaidani Granodiorite (Hida Mountain Range, central Japan) are determined based on Al-in-hornblende geobarometry and U–Pb zircon dating. Al-poor patchy replacements developed in amphiboles are common in this granite and petrographic study revealed that the replacements include chloritized biotite and albitic plagioclase. These are probably the hydrothermally recrystallized domains, and should not be used for solidification pressure estimates. Magmatic rim of amphibole is characterized by Si < 7.3 a.p.f.u. (Al_IV > 0.7 a.p.f.u.), and utilized in solidification pressure estimate that yielded 0.17–0.29 GPa. The solidification age of the granite is estimated as ~5.6–5.2 Ma using U–Pb zircon dating. From these data, the lower limit of an average denudation rate after ~5.6–5.2 Ma for the area where Shiaidani Granodiorite is exposed is estimated as 0.93–2.5 mm/year.  相似文献   

Trajectories of Moving Objects on a Network: Detection of Similarities,Visualization of Relations,and Classification of Trajectories     

Yukio Sadahiro  Raymond Lay  Tetsuo Kobayashi 《Transactions in GIS》2013,17(1):18-40

Development in techniques of spatial data acquisition enables us to easily record the trajectories of moving objects. Movement of human beings, animals, and birds can be captured by GPS loggers. The obtained data are analyzed by visualization, clustering, and classification to detect patterns frequently or rarely found in trajectories. To extract a wider variety of patterns in analysis, this article proposes a new method for analyzing trajectories on a network space. The method first extracts primary routes as subparts of trajectories. The topological relations among primary routes and trajectories are visualized as both a map and a graph‐based diagram. They permit us to understand the spatial and topological relations among the primary routes and trajectories at both global and local scales. The graph‐based diagram also permits us to classify trajectories. The representativeness of primary routes is evaluated by two numerical measures. The method is applied to the analysis of daily travel behavior of one of the authors. Technical soundness of the method is discussed as well as empirical findings.  相似文献   

Visualizing Diurnal Population Change in Urban Areas for Emergency Management     

Tetsuo Kobayashi  Richard M. Medina  Thomas J. Cova 《The Professional geographer》2013,65(1):113-130

There is an increasing need for a quick, simple method to represent diurnal population change in metropolitan areas for effective emergency management and risk analysis. Many geographic studies rely on decennial U.S. Census data that assume that urban populations are static in space and time. This has obvious limitations in the context of dynamic geographic problems. The U.S. Department of Transportation publishes population data at the transportation analysis zone level in fifteen-minute increments. This level of spatial and temporal detail allows for improved dynamic population modeling. This article presents a methodology for visualizing and analyzing diurnal population change for metropolitan areas based on this readily available data. Areal interpolation within a geographic information system is used to create twenty-four (one per hour) population surfaces for the larger metropolitan area of Salt Lake County, Utah. The resulting surfaces represent diurnal population change for an average workday and are easily combined to produce an animation that illustrates population dynamics throughout the day. A case study of using the method to visualize population distributions in an emergency management context is provided using two scenarios: a chemical release and a dirty bomb in Salt Lake County. This methodology can be used to address a wide variety of problems in emergency management.  相似文献