Estimation of the offshore form of tsunami waves     

Isamu Aida 《Journal of Oceanography》1972,28(5):220-227

Estimation of the offshore form of tsunami waves based on an observed tidegage record at a bay head is attempted by means of an impulse response method and a characteristics method. For several tsunamis in Onagawa Bay, the results estimated by both methods are compared with the observed data at an offshore station. The correlation coefficient between the estimated and the observed values is 0.9 to 0.95, and the present methods are proved to be practical. The validity of the characteristics method is further confirmed in the case of Ofunato Bay.  相似文献   

Seasonal Variations of Water Properties and the Baroclinic Flow Pattern in Toyama Bay under the Influence of the Tsushima Warm Current     

Satoshi Nakada  Yutaka Isoda  Isamu Uchiyama 《Journal of Oceanography》2005,61(5):943-952

The seasonal variations of water properties and the baroclinic flow pattern in the upper layer of Toyama Bay, where the shelf breaks in the passway of the eastward coastal branch of the Tsushima Warm Current, have been examined using temperature and salinity data from 26 local stations collected in the 32 years from 1963 through 1994. The results show that the flow pattern around the bay, as inferred from the distributions of the geopotential anomaly at 300 dbar and saline core water, changes remarkably from summer to autumn. There are two obvious inflows into Toyama Bay in a year. One is the surface inflow of less saline water from east of the Noto Peninsula as the coastal-trapped density-driven flow of the coastal branch during the transition from May to July. In September, this inflow is abruptly weakened by a transient northwestward reversal flow in the intermediate layer around 100 m depth. This reversal flow is accompanied by the temporary shallowness of the pycnoclines inside the bay. At that time, another inflow with more saline water of the year occurs in the intermediate layer. From November until January, this reversal flow disappears and a southeastward passing through-flow gradually intensifies across the bay mouth, accompanied by deepening of the pycnoclines inside the bay. According to our interannual analysis over the 32-year study period, this reversal flow has been a stable seasonal phenomenon, except for only 4 years, in which a local warm region or warm eddy developed just north of the Noto Peninsula.  相似文献   

Entropy in Markov chains and discrimination of cyclic patterns in lithologic successions     

Isamu Hattori 《Mathematical Geology》1976,8(4):477-497

The concept of Markov chains, applied to stratigraphic sections, is reliable in analyzing cyclic patterns in lithologic successions. Randomness in the occurrence of lithologies repeating in a succession is evaluated generally in terms of entropies which can be calculated for the Markov matrix equated with the succession. Two types of entropies pertain to every state; one is relevant to the Markov matrix expressing the upward transitions, and the other, relevant to the matrix expressing the downward transitions. The latter and the former with respect to a certain state, making an entropy set, correspond to the degree of randomness in its linking with the others which occur as the precursor and the successor, respectively. It is obvious that the entropy sets which are calculated for all state variables serve as a reliable criterion in the discrimination of cyclic pattern of the succession. We are able based on the entropy sets to classify the various patterns into asymmetric, symmetric, and random cycles, which are exhibited also in actual lithologic successions. The entropy sets are calculated for Markov matrices which have been reported from a number of areas in the world, and compared with the cyclic patterns supposed there. Entropy for the whole system of sedimentation also is introduced to discuss variability of the condition in the depositional processes.  相似文献   

Further evidence of normal mode Rossby waves     

Toshihiko Hirooka  Isamu Hirota 《Pure and Applied Geophysics》1989,130(2-3):277-289

Further observational evidence of normal mode Rossby waves with higher meridional mode numbers is presented with the aid of global data from the troposphere to the stratosphere over the period November 1979 through April 1986.It is shown, without using ana priori assumption of meridional structure, that the third antisymmetric modes of zonal wavenumbers 1 and 2,i.e., (1,4) and (2,4) modes, substantially exist in the real atmosphere. These modes are, however, easily influenced by the nonuniform background field even in the equinoctial season; amplitude submaxima near the equator are apt to be dubious in the upper stratosphere so that the prototype meridional structure becomes obscure. The period of the (1,4) mode often falls into that of the (1,3) mode, about 16 days. Hence, these two modes cannot be classified simply by their periods, but the separation is made by their meridional structure.An appearance calendar of various modes is also presented for the analysis period. It is found that each mode appears irregularly throughout the year and that the year-to-year variation is fairly large.  相似文献   

Rocket measurements of lower ionosphere electron density by propagation characteristics of VLF waves     

Isamu Nagano  Masayoshi Mambo  Iwane Kimura 《Planetary and Space Science》1978,26(3):219-227

The electron density profile in the lower ionosphere was determined from the right- and left-handed circularly polarized wave fields of a 40 kHz ground based signal observed by means of a rocket born receiver. Estimation of the electron density profile from 70 km up to 100 km was made under the condition for the values calculated by the full wave analysis to agree with the observed values. Results are presented for two rockets launched soon after sunset.  相似文献   

Photographic monitoring system for observing heavy free-falling objects: Multi-stage design packages of radioactive waste     

Akihiko Ito  Koki Ouchi  Isamu Hisa  Susumu Seki  Yoshio Seto  Shoji Kurashina 《Journal of Oceanography》1984,40(2):98-104

In the consideration of safety it is required that packages containing radioactive wastes when dumped at sea should keep their integrity and retain their contents until they reach the seabed. Packages containing simulated radioactive wastes (non-radioactive) were tested by a free-fall method at depthsca. 4,300 m in an area for dumping industrial waste off Shikoku Island. Since the weight of the largest package was 4,300 kg, special attention was paid to the connection of a buoyancy system with mooring rope. Descent and ascent velocities of the free-fall system were calculated prior to the experiment. A free-fall experiment with an extremely heavy object, heavier than ever previously reported, was accomplished without trouble by using the free-fall system. Recovery of a camera, flash-light, and other components was successful in each of the three experiments. Successive photographing of the package during descent was made and its integrity was observed using the photographs taken by the recovered camera. The packages remained intact during descent and at least for a short time after arrival on the seabed.  相似文献   

Comparison of AGASA data with CORSIKA simulation     

M. Nagano  D. Heck  K. Shinozaki  N. Inoue  J. Knapp 《Astroparticle Physics》2000,13(4):209-294

An interpretation of Akeno giant air shower array (AGASA) data by comparing the experimental results with the simulated ones by cosmic ray simulation for KASCADE (CORSIKA) has been made. General features of the electromagnetic component and low energy muons observed by AGASA can be well reproduced by CORSIKA. The form of the lateral distribution of charged particles agrees well with the experimental one between a few hundred metres and 2000 m from the core, irrespective of the hadronic interaction model studied and the primary composition (proton or iron). It does not depend on the primary energy between 10^17.5 and 10²⁰ eV as the experiment shows. If we evaluate the particle density measured by scintillators of 5 cm thickness at 600 m from the core S₀(600), suffix 0 denotes the vertically incident shower) by taking into account the similar conditions as in the experiment, the conversion relation from S₀(600) to the primary energy is expressed as E (eV)=2.15×10¹⁷S₀(600)^1.015 within 10% uncertainty among the models and composition used, which suggests the present AGASA conversion factor is the lower limit. Although the form of the muon lateral distribution fits well to the experiment within 1000 m from the core, the absolute values change with hadronic interaction model and primary composition. The slope of the ρ_μ(600) (muon density above 1 GeV at 600 m from the core) vs. S₀(600) relation in experiment is flatter than that in simulation of any hadronic model and primary composition. As the experimental slope is constant from 10¹⁵ to 10¹⁹ eV, we need to study this relation in a wide primary energy range to infer the rate of change of chemical composition with energy.  相似文献   

Variation of the southward interior flow of the North Pacific subtropical gyre,as revealed by a repeat hydrographic survey   总被引：2，自引：1，他引：1  

Akira Nagano  Hiroshi Ichikawa  Yasushi Yoshikawa  Shoichi Kizu  Kimio Hanawa 《Journal of Oceanography》2012,68(2):361-368

Baroclinic variations of the southward flow in the interior region of the North Pacific subtropical gyre are presented with five hydrographic sections from San Francisco to near Japan during 2004–2006. The volume transport averaged temperature of the interior flow, which varies vigorously by a maximum of 0.8°C, is negatively correlated with the transport in the layer of density 24.5–26.5σ _θ, associated with changes in the vertical current structure. Transport variation in this density layer is thus mainly responsible for the thermal impact of the interior flow on the heat transport of the subtropical gyre.  相似文献   

Dichothermal layer deepening in relation with halocline depth change associated with northward shrinkage of North Pacific western subarctic gyre in early 2000s     

Akira Nagano  Masahide Wakita  Shuichi Watanabe 《Ocean Dynamics》2016,66(2):163-172

In the western subarctic North Pacific, a wind-driven cyclonic circulation, called the western subarctic gyre (WSAG), exists. We examined year-to-year changes of the gyre and hydrographic structures, applying the altimetry-based gravest empirical mode (AGEM) method to hydrographic and altimetric sea surface height (SSH) data, and relation to the in situ variation of the temperature minimum layer, i.e., the dichothermal layer, depth at station K2 (47^° N, 160^° E). The AGEM-based geostrophic volume transport and the streamfunction of the WSAG in the top 1000-dbar layer show that the gyre changes substantially. From the late 1990s to the mid-2000s, the gyre shrunk northward. Due to the shrinkage, the halocline bottom, which is equivalent to the top of the main pycnocline, deepens at K2 outside the central part of the gyre. The downward displacement of the dichothermal layer at K2 was found to be significantly related to that of the underlying halocline due to the northward shrinkage of the WSAG.  相似文献   

Estimation of vertical water and heat fluxes in the semi-confined aquifers in tokyo metropolitan area,japan     

S. Dapaah-Siakwan  Isamu Kayane 《水文研究》1995,9(2):143-160

Groundwater circulation is known to be one of the agents responsible for the redistribution of geothermal energy by acting as a source or sink in the course of its movement through porous media. Heat transport in groundwater systems is considered to be a coupled process and the theory based on this was used to analyse temperature profiles of 30 thermally stable observation wells in a deep, semi-confined aquifer system in the Tokyo Metropolitan area. Vertical water fluxes in the semi-confined aquifers and the associated upward heat fluxes were estimated from a heat flux equation that describes convection and conduction processes of heat transport in one dimension. The vertical downward water fluxes in Shitamachi lowland, Musashino and Tachikawa terraces were 0.69.26.91 × 10^?9, 1.46-70.92 × 10^?9 and 2.61.2204 × 10^?9 m/s, respectively. A vertical upward water flux of 1.80-33.60 × 10^?9 m/s was estimated in Shitamachi lowland. The water flux generally decreased with increasing depth for observation wells which intercepted more than one semi-confining layer. The estimated upward heat fluxes for Shitamachi lowland, Musashino and Tachikawa terraces were 0.32-1.12, 0.49-1.21 and 1.00-11.62 W/m², respectively. The heat flux was highest in Tachikawa terrace where a major fault, the Tachikawa fault, is located. Generally, the estimated heat flux was higher in the semi-confining layers than in the aquifers. Areas with heat sources and sinks as well as groundwater flow patterns in the semi-confined aquifers were revealed by heat flux and temperature distributions in the study area.  相似文献