Sequential forecasting of the surface and subsurface conditions in the Japan Sea   总被引：1，自引：0，他引：1  

Naoki Hirose  Hideyuki Kawamura  Ho Jin Lee  Jong-Hwan Yoon 《Journal of Oceanography》2007,63(3):467-481

This study estimates a realistic change of the Japan Sea by assimilating satellite measurements into an eddy-resolving circulation model. Suboptimal but feasible assimilation schemes of approximate filtering and nudging play essential roles in the system. The sequential update of error covariance significantly outperforms the asymptotic covariance in the sequential assimilation due to the irregular sampling patterns from multiple altimeter satellites. The best estimates show an average rms difference of only 1.2°C from the radiometer data, and also explain about half of the sea level variance measured by the altimeter observation. The subsurface conditions associated with the mesoscale variabilities are also improved, especially in the Tsushima Warm Current region. It is demonstrated that the forecast limit strongly depends on variable, depth, and location.  相似文献   

Occurrence characteristics of chaetognath species along the PM transect in the Japan sea during 1972–2002     

Naoki Nagai  Kazuaki Tadokoro  Kazunori Kuroda  Takashige Sugimoto 《Journal of Oceanography》2006,62(5):597-606

A long-term variation in dominant species of chaetognaths in the Tsushima Warm Current was analyzed using samples collected four times a year from 1972 to 2002 by the Maizuru Marine Observatory along the PM transect in the Japan Sea. Of 19 occurring species, 13 subtropical species formed a major portion of the standing stock. Species richness in the study area was similar to that in the East China Sea and the South China Sea. Four species, Sagitta minima, S. nagae, S. enflata, S. elegans dominated in the upper 150 m water column. The most dominant species per season were S. minima in both winter and autumn, S. elegans in spring and S. nagae in summer. Water temperature and salinity ranges of the most frequent occurrence for three dominant species revealed a common tendency in the order of S. nagae > S. minima > S. enflata towards colder temperature and higher salinity. Inter-annual abundance of chaetognath species fluctuated proportionally in response to the warm or cool phases in water temperature. Water temperature was a fundamental factor in regulating distributional occurrence, being more decisive than salinity. Changes of both dominant species and species numbers in relation to the reduced abundance during winter to spring and the subsequent increase during summer to autumn might be caused by specific differences in optimum temperature. Chaetognath species are important as an indicator of water masses and significant for our understanding of changes and evaluations of the Japan Sea ecosystem.  相似文献   

Determination of rare earth elements,thorium and uranium in seaweed samples on the coast in Niigata Prefecture by inductively coupled plasma mass spectrometry     

Nobuo Sakamoto  Naoki Kano  Hiroshi Imaizumi 《Applied Geochemistry》2008

The determination of rare earth elements (REEs), Th and U in seaweeds of various species and in ambient surface seawater were performed by inductively coupled plasma mass spectrometry. The seaweeds and the seawater samples were collected at 10 different coastal areas of Niigata Prefecture in Japan twice a year (spring and autumn) in 2004 and 2005. Results showed that concentration of REEs in seaweed species from Niigata Prefecture were about 10³ times higher than those in seawater, and the enrichment factors of REEs were larger in heavy REE than light REE. A significant concentration difference of REEs, Th and U was found among species even in the same phylum. Undaria pinnatifida had the highest concentration of U. Considering that U. pinnatifida has low concentrations of REEs among typical brown algae, different REEs and U uptake mechanisms are suggested. The concentration of REEs, Th and U did not vary remarkably between sampling points and/or seasons.  相似文献   

A large-scale excavation in soft Holocene deposit and its elasto-viscoplastic analysis     

Fusao Oka  Naoki Takada  Kazuyuki Shimono  Yosuke Higo  Sayuri Kimoto 《Acta Geotechnica》2016,11(3):625-642

In the present study, the large-scale excavation in the construction is numerically back-analyzed using a soil–water-coupled finite element method with an elasto-viscoplastic model which considers the strain-induced degradation. The measurements of the deformation have been performed during the construction of a new railway station in Osaka, Japan, in which a large and deep excavation has been successfully carried out using a special deep mixing type of soil improvement method with earth retaining walls through the thick Holocene Osaka Umeda clay deposit. A comparison between the numerical results and the measurements of the excavation at Osaka shows that the simulation method can reproduce the overall deformation of the soft ground and the earth retaining walls including the time-dependent behaviour during the excavation and a deep mixing soil improvement method as an additional technique for stability are effective.  相似文献   

Soil pore characteristics of evergreen and deciduous forests of the tropical monsoon region in Cambodia     

Jumpei Toriyama  Seiichi Ohta  Makoto Araki  Ken'ichirou Kosugi  Tatsuhiko Nobuhiro  Naoki Kabeya  Akira Shimizu  Koji Tamai  Mamoru Kanzaki  Sophal Chann 《水文研究》2011,25(5):714-726

Both evergreen and deciduous forests (Efs and Dfs) are widely distributed under similar climatic conditions in tropical monsoon regions. To clarify the hydraulic properties of the soil matrix in different forest types and their effects on soil water storage capacity, the soil pore characteristics (SPC) were investigated in Ef and Df stands in three provinces in Cambodia. Soils in the Ef group were characterized in common by large amounts of coarse pores with moderate pore size distribution and the absence of an extremely low K_s at shallow depths, compared to Df group soils. The mean available water capacity of the soil matrix (AWC_sm) for all horizons of the Ef and Df group soils was 0·107 and 0·146 m³ m^?3, respectively. The mean coarse pore volume of the soil matrix (CPV_sm) in the Ef and Df groups was 0·231 and 0·115 m³ m^?3, respectively. A water flow simulation using a lognormal distribution model for rain events in the early dry season indicated that variation in SPC resulted in a larger increase in available soil water in Ef soils than in Df soils. Further study on deeper soil layers in Ef and each soil type in Df is necessary for the deeper understanding of the environmental conditions and the hydrological modelling of each forest ecosystem. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Migration dynamics of Pacific herring (Clupea pallasii) and response to spring environmental variability in the southeastern Bering Sea     

Naoki Tojo  Gordon H. Kruse  Fritz C. Funk 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2832

In the southeastern Bering Sea, Pacific herring (Clupea pallasii) migrate from the Pribilof Islands region where they overwinter, to the Alaska coast where they spawn in spring. The migration sustains a nearshore commercial fishery that targets roe-bearing females just prior to spawning. Herring also are taken as bycatch in groundfish trawl fisheries, where time and area closures in these fisheries are triggered by herring bycatch caps. Using herring bycatch data collected since the 1970s by National Marine Fisheries Service (NMFS) observers aboard groundfish fishing vessels, a retrospective analysis was conducted to describe the seasonal migration pattern of Pacific herring in the southeastern Bering Sea and to study its spatial and temporal variability. Observed changes in herring catch per unit of effort were compared with variability in climate and oceanographic conditions. The seasonal migration is complex, but annual shifts in migration routes and a possible northward shift of the overwintering grounds was identified. Pre-spawning herring aggregated in different areas depending on whether spawning occurred early or late in spring. The thermal structure of the ocean around the ice edge appears to influence herring migration timing and route as well as spawning date. Thus, on the basis of recent changes in sea-ice extent and duration, we suggest that the herring bycatch savings area that was developed from data collected in the 1980s should be revised to reflect prevailing conditions.  相似文献   

Towards improved snow water equivalent retrieval algorithms for satellite passive microwave data over the mountainous basins of western USA     

Naoki Mizukami  Sanja Perica 《水文研究》2012,26(13):1991-2002

Space‐borne passive microwave snow water equivalent (SWE) retrieval algorithms are attractive for continuous SWE monitoring over large mountainous areas. The performance of three SWE retrieval algorithms, which were considered relevant for operational purposes, was examined for each month over the Colorado River Basin. In addition, statistical post‐processing was tested as a means of improving the SWE estimates from each algorithm. The evaluation started with the so‐called Chang equation, which was a pioneer algorithm and is still used in practice. Successive attempts were then made to improve the algorithm's performance through the calibration of the equation's coefficient and through the inclusion of brightness temperature data from various frequency channels. The Chang equation consistently underestimated SWE with average bias between 30 mm in November and more than 300 mm in April and root mean square error (RMSE) exceeding 500 mm at many locations in April. The statistical post‐processing effectively removed the bias and reduced the RMSE by half for all the months. When the Chang equation's coefficients were calibrated at each site, biases were reduced by approximately 85%, and RMSE was reduced by 40%–50%. Finally, the multiple channel equations produced unbiased SWE estimates with RMSEs 50%–60% of those from the Chang equation. However, the statistical post‐processing did not reduce RMSE for both calibrated algorithms. The last algorithm produced the most reliable estimates for at‐site analysis, but its skill deteriorated when analyses were performed over larger areal extents; therefore, it is only recommended for SWE monitoring over smaller areas. For larger areas, the calibrated Chang equation is desirable because it only requires interpolations of a calibrated coefficient, which was spatially coherent. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

The evolution of baryon density fluctuations in multicomponent cosmological simulations     

Naoki Yoshida  Naoshi Sugiyama  Lars Hernquist 《Monthly notices of the Royal Astronomical Society》2003,344(2):481-491

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Gas cooling in simulations of the formation of the galaxy population     

Naoki Yoshida  Felix Stoehr  Volker Springel  Simon D. M. White 《Monthly notices of the Royal Astronomical Society》2002,335(3):762-772

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Aerodynamic Parameters of Urban Building Arrays with Random Geometries   总被引：5，自引：5，他引：0  

Sheikh Ahmad Zaki  Aya Hagishima  Jun Tanimoto  Naoki Ikegaya 《Boundary-Layer Meteorology》2011,138(1):99-120

It is difficult to describe the flow characteristics within and above urban canopies using only geometrical parameters such as plan area index (λ _p ) and frontal area index (λ _f ) because urban surfaces comprise buildings with random layouts, shapes, and heights. Furthermore, two types of ‘randomness’ are associated with the geometry of building arrays: the randomness of element heights (vertical) and that of the rotation angles of each block (horizontal). In this study, wind-tunnel experiments were conducted on seven types of urban building arrays with various roughness packing densities to measure the bulk drag coefficient (C _d ) and mean wind profile; aerodynamic parameters such as roughness length (z _o ) and displacement height (d) were also estimated. The results are compared with previous results from regular arrays having neither ‘vertical’ nor ‘horizontal’ randomness. In vertical random arrays, the plot of C _d and z _o versus λ _f exhibited a monotonic increase, and z _o increased by a factor of almost two for λ _f = 48–70%. C _d was strongly influenced by the standard deviation of the height of blocks (σ) when λ _p ≥ 17%, whereas C _d was independent of σ when λ _p = 7%. In the case of horizontal random arrays, the plot of the estimated C _d against λ _f showed a peak. The effect of both vertical and horizontal randomness of the layout on aerodynamic parameters can be explained by the structure of the vortices around the blocks; the aspect ratio of the block is an appropriate index for the estimation of such features.  相似文献