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51.
The atmospheric mixed layer obtained using the Mellor–Yamada model grows slower and becomes shallower than observed, which motivated Nakanishi and Niino (J Meteorol Soc Jpn 87:895–912, 2009) to present a modified version of the Mellor–Yamada model. In this study, incorporating each of the Mellor–Yamada and the Nakanishi–Niino models into an ocean general circulation model, we evaluate its performance in the ocean. Comparing the numerical results with the observed ones in the western North Pacific, the Nakanishi–Niino model is shown to exhibit a better performance than the Mellor–Yamada model under strong wind forcing and sea surface cooling during winter and after passage of typhoons during summer. 相似文献
52.
Maya P. Bhatt Toshiyuki Masuzawa Mineko Yamamoto Kevin H. Gardner 《Environmental Geology》2009,57(3):557-569
Surface water samples were collected from Langtang Lirung glacier outlet point to the Narayani river system in central Nepal
in order to investigate the role of elevation in the variation of chemistry along the drainage networks. The chemistry of
Langtang–Narayani river system was dominated by sulfide oxidation coupled with carbonate dissolution and weathering of silicate
minerals. Calcium and magnesium concentrations were relatively higher than other cations and the sum of both species strongly
correlated with alkalinity, supporting the dissolution of carbonate and dolomite as the dominant source for these ions. Aluminosilicate
minerals primarily as albite and anorthite appeared as dominant silicate minerals within the drainage basin. Bisiallitization
was the dominant type of weathering within the entire drainage system. Hydrogen ion concentration was lower in the low elevation
sites than in high elevation sites reflecting the more consumption of carbon dioxide in the low elevation sites due to enhanced
chemical weathering rates. Furthermore, major solutes like sum of base cations, silicon as well as alkalinity increased in
concentration in the lower elevation sites. All regulating factors appeared to be directly related to elevation and hence
elevation appeared to be the prime factor for the variation in chemical species along the Langtang–Narayani river system.
Toshiyuki Masuzawa: deceased. 相似文献
53.
Short-Range Prediction Experiments with Operational Data Assimilation System for the Kuroshio South of Japan 总被引:3,自引:3,他引:3
Masafumi Kamachi Tsurane Kuragano Satoshi Sugimoto Kumi Yoshita Toshiyuki Sakurai Toshiya Nakano Norihisa Usui Francesco Uboldi 《Journal of Oceanography》2004,60(2):269-282
The short-range (one month) variability of the Kuroshio path was predicted in 84 experiments (90-day predictions) using a
model in an operational data assimilation system based on data from 1993 to 1999. The predictions started from an initial
condition or members of a set of initial conditions, obtained in a reanalysis experiment. The predictions represent the transition
from straight to meander of the Kuroshio path, and the results have been analyzed according to previously proposed mechanisms
of the transition with eddy propagation and interaction acting as a trigger of the meander and self-sustained oscillation.
The reanalysis shows that the meander evolves due to eddy activity. Simulation (no assimilation) shows no meander state, even
with the same atmospheric forcing as the prediction. It is suggested therefore that the initial condition contains information
on the meander and the system can represent the evolution. Mean (standard deviation) values of the axis error for all 84 cases
are 13, 17, and 20 (10, 10, and 12) km, in 138.5°E, in the 30-, 60-, and 90-day predictions respectively. The observed mean
deviation from seasonal variation is 30 km. The predictive limit of the system is thus about 80 days. The time scale of the
limit depends on which stage in the transition is adopted as the initial condition. The gradual decrease of the amplitude
in a stage from meander to straight paths is also predicted. The predictive limit is about 20 days, which is shorter than
the prediction of the opposite transition.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
54.
Using a vertically two-dimensional, two-layer model, we have analytically examined the generation mechanism of a nonzero Eulerian
residual flow by strong tide-topography interaction in a narrow channel where the frictional effect is not included. In this
case, tidally generated baroclinic disturbances are forced non-uniformly in space and time while being advected by a strong tidal flow over the non-uniform slope of the bottom topography. Consequently, nonzero Eulerian residual flow results when averaged over one tidal period.
Although the time average of the velocity field is thus nonzero, the associated Eulerian residual transport in each layer
is compensated by a Stokes transport so that no Lagrangian residual transport results in both layers. This warns us that simple
time averaging of the velocity data obtained at a fixed mooring station might lead to a spurious material transport.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
55.
Numerical study on wave-induced filtration flow across the beach face and its effects on swash zone sediment transport 总被引:2,自引:0,他引:2
A numerical model, coupling an analysis of beach groundwater flow with an analysis of swash wave motion over a uniform slope, is presented. Model calculations are performed to investigate the variations of swash-induced filtration flows across the beach face for different input parameters. Swash zone sediment transport under the influence of such filtration flow across the beach face is investigated through modification of effective weight of sediment particle and modification of swash boundary layer thickness. These effects are quantified based on a bed load transport model with a modified Shields parameter. 相似文献
56.
Shun Yukawa Yustiawati M. Suhaemi Syawal Kenichi Kobayashi Toshiyuki Hosokawa Takeshi Saito Shunitz Tanaka Masaaki Kurasaki 《Environmental Earth Sciences》2014,71(4):1945-1952
The pollution of water by heavy metals is one of the most serious problems in the developing countries, where watercourses play important roles in transport and economic activities. The aim of this study was to examine whether Hyposarcus pardalis, a fish species widespread in the freshwater environment in Indonesia, could be used as a biomarker for environmental pollution by metals. To this effect, the concentrations of metallothioneins and metals in the livers and kidneys of H. pardalis were measured. In addition, to clarify the relationship between metallothionein concentrations and metal exposure, the concentrations of metallothioneins and metals were determined in the liver and the kidney of fish exposed to 50 and 500 ppb Cu and 500 ppb Mn, compared with those kept in clean water. Sufficient concentrations of metallothionein were detected in fish captured from Lake Rawakalong located in an industrial area in the suburbs of Jakarta. The results of exposure experiments suggested that H. pardalis retained a history of pollution in its organs for a long duration, and the metals bound to metallothioneins in the liver and kidney could be replaced with Cu following exposure. In conclusion, the hepatic and renal metallothioneins in H. pardalis are a useful candidate biomarker for monitoring heavy metal contamination. 相似文献
57.
Study of a Bistatic Radar System Using VLBI Technologies for Detecting Space Debris and the Experimental Verification of its Validity 总被引:1,自引:0,他引:1
Masanobu Yajima Kazutomo Tsuchikawa Toshiyuki Murakami Kazuyoshi Katsumoto Tadashi Takano 《Earth, Moon, and Planets》2007,100(1-2):57-76
Space debris are increasing around the Earth. The observation of space debris is a key issue for the investigation and monitoring
of space environment. But the observation opportunities and the detection ability are limited in existing monostatic radar
systems. This paper proposes a bistatic radar which is composed of a transmitting station and a receiving-only station. A
carrier wave modulated by PN-PSK signals is used in combination with a VLBI (Very Long Baseline Interferometry) recorder for
range measurement between space debris and stations. The receiving radio wave is processed on the basis of VLBI techniques.
Accordingly, the system is shown to have significant advantages over a monostatic radar. We actually formed a bistatic radar
system, and observed a satellite in order to experimentally verify the validity. The configuration of the system, data analysis
and the experimental results are described. 相似文献
58.
Manchuk Nuramkhaan Toshiyuki Kurihara Kazuhiro Tsukada Yoshikazu Kochi Hokuto Obara Tatsuya Fujimoto Yuji Orihashi Koshi Yamamoto 《Island Arc》2013,22(4):494-507
The dating of radiolarian biostratigraphic zones from the Silurian to Devonian is only partially understood. Dating the zircons in radiolarian‐bearing tuffaceous rocks has enabled us to ascribe practical ages to the radiolarian zones. To extend knowledge in this area, radiometric dating of magmatic zircons within the radiolarian‐bearing Hitoegane Formation, Japan, was undertaken. The Hitoegane Formation is mainly composed of alternating beds of tuffaceous sandstones, tuffaceous mudstones and felsic tuff. The felsic tuff and tuffaceous mudstone yield well‐preserved radiolarian fossils. Zircon grains showing a U–Pb laser ablation–inductively coupled plasma–mass spectrometry age of 426.6 ± 3.7 Ma were collected from four horizons of the Hitoegane Formation, which is the boundary between the Pseudospongoprunum tauversi to Futobari solidus–Zadrappolus tenuis radiolarian assemblage zones. This fact strongly suggests that the boundary of these assemblage zones is around the Ludlowian to Pridolian. The last occurrence of F. solidus is considered to be Pragian based on the reinterpretation of a U–Pb sensitive high mass‐resolution ion microprobe (SHRIMP) zircon age of 408.9 ± 7.6 Ma for a felsic tuff of the Kurosegawa belt, Southwest Japan. Thus the F. solidus–Z. tenuis assemblage can be assigned to the Ludlowian or Pridolian to Pragian. The present data also contribute to establishing overall stratigraphy of the Paleozoic rocks of the Fukuji–Hitoegane area. According to the Ordovician to Carboniferous stratigraphy in this area, Ordovician to Silurian volcanism was gradually reduced to change the sedimentary environment into a tropical lagoon in the early Devonian. And the quiet Carboniferous environment was subsequently interrupted, throwing it once more into the volcanic conditions in the Middle Permian. 相似文献
59.
60.
We dynamically downscaled Japanese reanalysis data (JRA-25) for 60 regions of Japan using three regional climate models (RCMs): the Non-Hydrostatic Regional Climate Model (NHRCM), modified RAMS version 4.3 (NRAMS), and modified Weather Research and Forecasting model (TWRF). We validated their simulations of the precipitation climatology and interannual variations of summer and winter precipitation. We also validated precipitation for two multi-model ensemble means: the arithmetic ensemble mean (AEM) and an ensemble mean weighted according to model reliability. In the 60 regions NRAMS simulated both the winter and summer climatological precipitation better than JRA-25, and NHRCM simulated the wintertime precipitation better than JRA-25. TWRF, however, overestimated precipitation in the 60 regions in both the winter and summer, and NHRCM overestimated precipitation in the summer. The three RCMs simulated interannual variations, particularly summer precipitation, better than JRA-25. AEM simulated both climatological precipitation and interannual variations during the two seasons more realistically than JRA-25 and the three RCMs overall, but the best RCM was often superior to the AEM result. In contrast, the weighted ensemble mean skills were usually superior to those of the best RCM. Thus, both RCMs and multi-model ensemble means, especially multi-model ensemble means weighted according to model reliability, are powerful tools for simulating seasonal and interannual variability of precipitation in Japan under the current climate. 相似文献