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排序方式: 共有227条查询结果,搜索用时 31 毫秒
31.
Yasumasa Miyazawa Toru Miyama Sergey M. Varlamov Xinyu Guo Takuji Waseda 《Ocean Dynamics》2012,62(4):645-659
We investigated the feasibility of the ensemble Kalman filter (EnKF) to reproduce oceanic conditions south of Japan. We have
adopted the local ensemble transformation Kalman filter algorithm based on 20 members’ ensemble simulations of the parallelized
Princeton Ocean Model (the Stony Brook Parallel Ocean Model) with horizontal resolution of 1/36°. By assimilating satellite
sea surface height anomaly, satellite sea surface temperature, and in situ temperature and salinity profiles, we reproduced
the Kuroshio variation south of Japan for the period from 8 to 28 February 2010. EnKF successfully reproduced the Kuroshio
path positions and the water mass property of the Kuroshio waters as observed. It also detected the variation of the steep
thermohaline front in the Kii Channel due to the intrusion of the Kuroshio water based on the observation, suggesting efficiency
of EnKF for detection of open and coastal seas interactions with highly complicated spatiotemporal variability. 相似文献
32.
Fuminori Hashihama Toru Hirawake Sakae Kudoh Jota Kanda Ken Furuya Yukuya Yamaguchi Takashi Ishimaru 《Polar Science》2008,2(2):109-120
We investigated the size fraction and pigment-derived class compositions of phytoplankton within the euphotic zone of the Antarctic marginal ice zone between 63.3°S and 66.5°S along the 140°E meridian on two consecutive cruises in the late austral summer and early austral autumn of 2003. We observed significant temporal and spatial variations in phytoplankton size and taxonomic composition, although chlorophyll a concentrations were generally below 1 μg l−1 during both periods. Microphytoplankton (>20 μm), mainly diatoms, were prominent in the euphotic zone in the southernmost area around 66.5°S during late summer. In the rest of the study area during both cruises, the phytoplankton community was dominated by pico- and nano-sized populations (<20 μm) throughout the euphotic zone. The small-size populations mostly consisted of diatoms and haptophytes, although chlorophytes were dominant in extremely cold water (−1.5°C) below the overlying warm water around 65.5°S during late summer. From late summer to early autumn, chlorophytes declined in abundance, probably due to increasing temperature within the euphotic zone (−1 to 0°C). These pico- and nano-phytoplankton-dominated populations were often accompanied by relatively high concentrations of ammonium, suggesting the active regeneration of nutrients within the small-size plankton community. 相似文献
33.
34.
日本原子能机构(Japan Atomic Energy Agency)提出了一种方法,即通过地表原地应力测量所得的有限数据精确估算任意一点的实际原地应力状态分布.我们假定实际地应力是由上覆岩层压力和板块构造力的综合作用形成的,并建立了两种模型:三维有限元模型和边界元模型,模型考虑了地质情况的不均匀性,如岩石类型的变化和... 相似文献
35.
Paleocene large-scale normal faulting along the Median Tectonic Line, western Shikoku, Japan 总被引:1,自引:0,他引:1
Abstract The Median Tectonic Line (MTL) in southwest Japan, a major east–west-trending arc-parallel fault, has been defined as the boundary fault between the Cretaceous Sambagawa metamorphic rocks and Ryoke granitic and metamorphic rocks, which are unconformably covered by the Upper Cretaceous Izumi Group. The juxtaposition by faulting occurred after the deposition of the Izumi Group. Based on detailed fieldwork and previous studies, the authors reconstruct the kinematic history along the MTL during the Paleogene period, which has not been fully understood before. It is noted that although the strata of the Izumi Group along the MTL dip gently, east–west-trending north-vergent folds with the wavelength of ∼300 m commonly develop up to 2 km north from the MTL. Along the MTL, a disturbed zone of the Izumi Group up to 400 m thick, defined by the development of boudinage structures with the transverse boudin axis dipping nearly parallel to the MTL, occurs. Furthermore, east–west-trending north-vergent folds with the wavelength of 1–5 m develop within the distance up to 60 m from the MTL. The disturbed zone with the map-scale north-vergent folds along the MTL, strongly suggests that they formed due to normal faulting with a top-to-the-north sense along the MTL. Considering that the normal faulting is associated with the final exhumation of the Sambagawa metamorphic rocks, and its juxtaposition against the Izumi Group at depth, this perhaps occurred before the denudation of the Sambagawa metamorphic rocks indicated by the deposition of the Lower Eocene Hiwada-toge Formation. Dynamic equilibrium between crustal thickening at depth (underplating) and extension at shallow level is a plausible explanation for the normal faulting because the arc-normal extension suggests gravity as the driving force. 相似文献
36.
37.
Thermodynamic analysis of Fe and Mg partitioning between plagioclase and silicate liquid 总被引:4,自引:0,他引:4
Toru Sugawara 《Contributions to Mineralogy and Petrology》2000,138(2):101-113
Thermodynamic analysis of Fe- and Mg-bearing plagioclase and silicate liquid was carried out based on reported element partitioning
data between plagioclase and silicate liquid in reduced conditions, solution properties of ternary feldspar, standard state
properties of plagioclase endmembers and solution properties of multicomponent silicate liquid. Derived mixing properties
of Fe- and Mg-bearing plagioclase are in harmony with estimated results from synthetic experiments in the systems CaAl2Si2O8-CaFeSi3O8 and CaAl2Si2O8-CaMgSi3O8. Based on the determined solution properties of the plagioclase, a computer program to calculate the element partition relationships
between Fe- and Mg-bearing plagioclase and multicomponent silicate liquid was developed. The FeO, MgO and MgO/(MgO + FeO)
in plagioclase predicted from known liquid compositions and pressure are in agreement with measurements within 0.2 wt%, 0.1 wt%
and 0.1 (mol ratio), respectively. The Fe3+ content in plagioclase crystallized at high oxygen fugacity can be estimated with this program. The Fe3+/total Fe ratio in plagioclase crystallized near the quartz-fayalite-magnetite buffer ranges from 0 to 0.5, which is consistent
with previous study on natural plagioclase in submarine basalt. Derived solution properties of the Fe- and Mg-bearing plagioclase
are also used to calculate equilibrium composition relationship between olivine and plagioclase. Change of X
Fo in olivine coexisting with plagioclase affects MgO and FeO contents in plagioclase greatly. The present model predicts X
Fo of coexisting olivine from the chemical composition of plagioclase to ±0.1 accuracy at given pressure and temperature.
Received: 27 March 1998 / Accepted: 30 September 1999 相似文献
38.
39.
Upper Mantle Velocity Structure Estimated From Ps-Converted Wave Beneath the North-Eastern Japan Arc 总被引:2,自引:0,他引:2
Toru Matsuzawa Norihito Umino Akira Hasegawa Akio Takagi 《Geophysical Journal International》1986,86(3):767-787
Summary. The upper boundary of the descending oceanic plate is located by using PS -waves (converted from P to S at the boundary) in the Tohoku District, the north-eastern part of Honshu, Japan. the observed PS-P time data are well explained by a two-layered oceanic plate model composed of a thin low-velocity upper layer whose thickness is less than 10 km and a thick high-velocity lower layer; the upper and lower layers respectively have 6 per cent lower and 6 per cent higher velocity than the overriding mantle. the estimated location of the upper boundary is just above the upper seismic plane of the double-planed deep seismic zone. This result indicates that events in the upper seismic plane, at least in the depth range from 60 to 150 km, occur within the thin low-velocity layer on the surface of the oceanic plate. 相似文献
40.
Fumie Murata Toru Terao Taiichi Hayashi Haruhisa Asada Jun Matsumoto 《Natural Hazards》2008,44(3):399-410
To improve flood forecasting, the understanding of the atmospheric conditions associated with severe rainfall is crucial.
We analysed the atmospheric conditions at Dhaka, Bangladesh, using upper-air soundings. We then compared these conditions
with daily rainfall variations at Cherrapunjee, India, which is a main source of floodwater to Bangladesh, and a representative
sample of exceptionally heavy rainfall events. The analysis focussed on June and July 2004. June and July are the heaviest
rainfall months of the year at Cherrapunjee. July 2004 had the fourth-heaviest monthly rainfall of the past 31 years, and
severe floods occurred in Bangladesh. Active rainfall periods at Cherrapunjee corresponded to “breaks” in the Indian monsoon.
The monsoon trough was located over the Himalayan foothills, and strong westerly winds dominated up to 7 km at Dhaka. Near-surface
wind below 1 km had southerly components, and the wind profile had an Ekman spiral structure. The results suggest that rainfall
at Cherrapunjee strongly depends on the near-surface wind speed and wind direction at Dhaka. Lifting of the near-surface southerly
airflow by the Meghalaya Plateau is considered to be the main contributor to severe rainfall at Cherrapunjee. High convective
available potential energy (CAPE) also contributes to intense rainfall. 相似文献