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The Kuroshio, one of the most energetic western boundary currents in the world, shows variations in its mesoscale features and recirculation gyres, providing an excellent test case of interactions between the mesoscale field and Kuroshio Extension (KE) states. A three-layer quasi-geostrophic model was used to reconstruct flow fields continuous in time and the horizontal plane from the TOPEX/POSEIDON altimeter data based on the variational method. Compared with the solutions obtained by the nudging method, the present results proved that the variational solution was closer to the real field. In the assimilation period, 1993–1997, the baroclinic instability index (BII) was defined to be the phase shift from the uppermost layer to the lowest layer with mesoscale features. In the first half of the assimilation period, the KE took the transition from the elongated to contracted states, in which BII decreased gradually, as a consequence of the KE state shift. In the second half period, BII increased in the downstream region just west of the Shatsky Rise, in which baroclinic instability contributed to the final stage of the contracted state, and was followed by rapidly weakened instability as a trigger of the opposite transition from the contracted to elongated states. The wind-driven recirculation gyre played an active role on the KE transition in the first half period, although not in the second half. 相似文献
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Yosuke Maeda 《Geoforum》2012,43(2):342-352
The recent development of the third sector and the government encouragement of it have attracted the attention of many researchers. In particular, geographical research has examined how the third sector has been affected or changed by government policies or guidelines in recent political economic contexts, especially neo-liberalism and also neo-communitarianism. While much research has demonstrated that the relationship between the government and the third sector is becoming closer, and has considered the problematic impact on the sector or the community, recent studies have described a much more complicated relationship and its consequence. In response, this paper attempts to explore alternative effects of government encouragement at the local community level, through utilising empirical data on recent voluntary activity regarding community safety by the Voluntary Organisations for Crime Prevention Patrol (VOCPP) in Musashino City, a suburb of Tokyo in Japan. Before focusing on the case study in Musashino, the paper briefly outlines key geographical literature on the third sector, and also examines recent expectations of Japan’s third sector using Japanese political documents. Finally, the paper argues that the encouragement of government in fact has the potential to work as a ‘catalyst’ leading to a more independent third sector, with a geographically and organisationally less hierarchical structure, and may also assist in developing a more diversified community. 相似文献
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Norihisa?UsuiEmail author Shiro?Ishizaki Yosuke?Fujii Masafumi?Kamachi 《Journal of Oceanography》2011,67(3):253-262
We assess validity of a Gaussian error assumption, the basic assumption in data assimilation theory, and propose two kinds
of constraints regarding non-Gaussian statistics. In the mixed water region (MWR) off the east coast of Japan exhibiting complicated
frontal structures, a probability density function (PDF) of subsurface temperature shows double peaks corresponding to the
Kuroshio and Oyashio waters. The complicated frontal structures characterized by the temperature PDF sometimes cause large
innovations, bringing about a non-Gaussianity of errors. It is also revealed that assimilated results with a standard three-dimensional
variational (3DVAR) scheme have some issues in MWR, arising from the non-Gaussianity of errors. The Oyashio water sometimes
becomes unrealistically cold. The double peaks seen in the observed temperature PDF are too smoothed. To improve the assimilated
field in MWR, we introduce two kinds of constraints, J
c1 and J
c2, which model the observed temperature PDF. The constraint J
c1 prevents the unrealistically cold Oyashio water, and J
c2 intends to reproduce the double peaks. The assimilated fields are significantly improved by using these constraints. The
constraint J
c1 effectively reduces the unrealistically cold Oyashio water. The double peaks in the observed temperature PDF are successfully
reproduced by J
c2. In addition, not only subsurface temperature but also whole level temperature and salinity (T–S) fields are improved by
adopting J
c1 and J
c2 to a multivariate 3DVAR scheme with vertical coupled T–S empirical orthogonal function modes. 相似文献
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Masahide Aikawa Takatoshi Hiraki Yosuke Horie Ryouhei Nakatsubo Chisato Matsumura Hitoshi Mukai 《Journal of Atmospheric Chemistry》2017,74(4):505-518
The seasonal intensive sampling of gases and particulate matter in ambient air was conducted at the site established in urban area of Japan to study the seasonal difference of the temporal variation of gases and particulate matter concentrations in urban atmosphere as well as to illustrate the different transport regimes that impacts air pollutants. The sample was collected by the four-stage filter-pack method with 6-h interval for one week in four seasons (spring, summer, autumn and winter). The trans-boundary transport of air pollutants with high concentration was characteristically observed in the spring sampling. On the other hand, we could successfully detect the in-country transports of air pollutants in the summer sampling. Four-season’s intensive survey considered, we could show the characteristic transport of air pollutants to provide the episodic high concentration for ambient air in the urban area of Japan, and successfully illustrate the seasonal-dependent transport regimes to impact on air pollutants. 相似文献
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Simple monitoring method for precaution of landslides watching tilting and water contents on slopes surface 总被引：2，自引：2，他引：0
Taro Uchimura Ikuo Towhata Trinh Thi Lan Anh Jou Fukuda Carlos J. B. Bautista Lin Wang Ichiro Seko Taro Uchida Akira Matsuoka Yosuke Ito Yuichi Onda Sho Iwagami Min-Seok Kim Naoki Sakai 《Landslides》2010,7(3):351-357
A low-cost and simple monitoring method for early warning of landslides is proposed. To detect abnormal deformation of a slope, this method employs a tilt sensor in place of an extensometer on the slope surface. In order to examine the relevance of measuring rotation angle on a slope surface by tilt sensor, model tests were conducted, and rotation on the slope surface was observed together with slide displacement along the surface. The rotation data responded 30 min before failure in a model test, which could be useful as a signal for early warning. However, the behavior of rotation before failure varies from case to case, and thus, criteria to issue warning should be defined more carefully. For a model slope made of uniform loose sand, measurement of slide displacement along the slope surface is sensitive to failure at the toe, while the measurement of rotation on the slope surface is useful to detect the development of progressive failure upward along the slope. Wireless sensor units with microelectromechanical systems (MEMS) tilt sensor and volumetric water content sensor were also examined on a real slope in Kobe City, and a long-term monitoring was attempted. A simple but possible way to define the criteria of judgment to issue warning can be proposed based on combination of data obtained by the tilt sensors and volumetric water content sensors. 相似文献
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—?In order to clarify the effects of contact geometry of faults on transmission waves, we have performed a series of experiments in which P and S waves with known wavelength were transmitted through an artificial fault. A pair of piezo-electric transducers (PZT) with various resonant frequency were used for the transmitter and the receiver. Parallel grooves were cut on disk surfaces and two disks were placed face to face with the grooves on one disk being perpendicular to those on the other disk. This yields evenly spaced square contacts on the fault. We regard the square contacts as asperity contacts, the size and the height of which were controlled by changing the width and the depth of the grooves. We found that the transmissivity of the waves is solely determined by the ratio of the groove depth/width to wavelength. The shallower and the narrower the groove depth and width are, the larger the amplitude of first arrival is for both P and S waves. When the groove depth is shallower than a quarter of wavelength, the effect of groove depth is negligible; deeper grooves significantly reduce the amplitude. We have made a mathematical model based on the stiffness of fault. By comparing the model calculations with the observation we found that the model has a limit at which the prediction by the model deviates from the data. The deviation occurs when the ratio of the groove depth/width to wavelength becomes 0.25. We refer to the wavelength as the critical wavelength. When the wavelength is larger than the critical wavelength, the observed data can be well explained by the model. Above this threshold, the model no longer fits the data. In this range, the amplitude of transmitted waves is found to be proportional to the real contact area. Although it is a kind of paradox that the amplitude, not the energy, is proportional to the real contact area, it is possibly explained by taking a non-uniform distribution of stress on the surface of the receiver PZT into account. 相似文献
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Short-range prediction experiments of the Kuroshio path variabilities south of Japan 总被引：1，自引：0，他引：1
Assimilation and prediction experiments of the Kuroshio path variability south of Japan were conducted to investigate the
predictability of the Kuroshio path. The assimilation and prediction system is composed of an eddy-resolving model and a three-dimensional
variational analysis scheme with vertical coupled temperature–salinity empirical orthogonal function modes. The sea surface
height (SSH) variability and the variations of the Kuroshio path of the assimilation fields are in good agreement with those
observed. The results of the assimilation are then used as the initial conditions for 138 cases of 90-day prediction experiments
conducted from 1993 to 2004. The predictive limit of our system is assessed by the SSH anomaly in the assimilation field and
is found to be around 40–60 days, which is much longer than that of the persistence. The prediction results show good performance
in the transition stage from a straight to a meandering path. For example, a large meandering event that occurred in August
2004 is successfully predicted in a 2-month forecast. Two types of failure cases are investigated. One is a case where the
eastward propagation speed of the meander is faster than a real state. The dynamical response of the model to the assimilation
revealed that an initial shock, caused by the dynamically unbalanced initial condition, induces the fast eastward propagation
of the meander. The other case exhibits an unrealistic meander. In this case, a cold anomaly at an intermediate layer in the
initial condition grows rapidly and results in the unrealistic meander. This implies that the Kuroshio path south of Japan
has a chaotic nature. These facts revealed by the failure cases give us some insight for improving the predictive skill of
the Kuroshio path variability. 相似文献
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