Errata: Intermediate Circulation in the Northwestern North Pacific Derived from Subsurface Floats     

Takanori Iwao  Masahiro Endoh  Nobuyuki Shikama  Toshiya Nakano 《Journal of Oceanography》2004,60(2):517-517

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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   

Preferential dissolution of SiO<Subscript>2</Subscript> from enstatite to H<Subscript>2</Subscript> fluid under high pressure and temperature     

Ayako Shinozaki  Hiroyuki Kagi  Hisako Hirai  Hiroaki Ohfuji  Taku Okada  Satoshi Nakano  Takehiko Yagi 《Physics and Chemistry of Minerals》2016,43(4):277-285

Stability and phase relations of coexisting enstatite and H₂ fluid were investigated in the pressure and temperature regions of 3.1–13.9 GPa and 1500–2000 K using laser-heated diamond-anvil cells. XRD measurements showed decomposition of enstatite upon heating to form forsterite, periclase, and coesite/stishovite. In the recovered samples, SiO₂ grains were found at the margin of the heating hot spot, suggesting that the SiO₂ component dissolved in the H₂ fluid during heating, then precipitated when its solubility decreased with decreasing temperature. Raman and infrared spectra of the coexisting fluid phase revealed that SiH₄ and H₂O molecules formed through the reaction between dissolved SiO₂ and H₂. In contrast, forsterite and periclase crystals were found within the hot spot, which were assumed to have replaced the initial orthoenstatite crystals without dissolution. Preferential dissolution of SiO₂ components of enstatite in H₂ fluid, as well as that observed in the forsterite H₂ system and the quartz H₂ system, implies that H₂-rich fluid enhances Mg/Si fractionation between the fluid and solid phases of mantle minerals.  相似文献   

Effect of seasonal forcing on global circulation in a world ocean general circulation model     

H. Nakano  R. Furue  N. Suginohara 《Climate Dynamics》1999,15(7):491-502

 Effects of the seasonal variation in thermohaline and wind forcing on the abyssal circulation are investigated by using an ocean general circulation model. To isolate effects of the seasonality in the thermohaline forcing from those in the wind forcing, we carry out three experiments with (1) annual-mean wind forcing and perpetual-winter thermohaline forcing, (2) annual-mean wind forcing and seasonal thermohaline forcing, and (3) seasonal wind forcing and seasonal thermohaline forcing. The deep water under the seasonal thermohaline forcing becomes warmer than under the perpetual-winter thermohaline forcing. Although the perpetual-winter thermohaline forcing is widely used and believed to reproduce the deep water better than the annual-mean forcing, the difference between the results of the perpetual-winter and the seasonal thermohaline forcing is significant. The seasonal variation of the Ekman convergence and divergence produces meridional overturning cells extending to the bottom because the period of seasonal cycle is shorter than the adjustment timescale by baroclinic Rossby waves. The heat transport owing to those Ekman flows and temperature anomalies makes the upper water (0–200 m) colder at low to mid-latitudes (40S–40N) and warmer at high latitudes. Also the deep water becomes warmer owing to the warming of the northern North Atlantic, the main source region of North Atlantic Deep Water. The model is also synchronously (i.e., without acceleration) integrated with seasonal forcing for 5400 y. A past study suggested that under seasonal forcing, a sufficient equilibrium state can be achieved after only decades of synchronous integration following more than 10 000 y of accelerated integration. Here, the result so obtained is compared with that of the 5400-y synchronous integration. The difference in the global average temperature is as small as 0.12 °C, and most of the difference is confined to the Southern Ocean. Received: 1 May 1998 / Accepted: 5 January 1999  相似文献   

A hybrid approach for deriving horizontal site amplification factors considering both the similarity of HVSRE and the vertical amplification correction function     

Ziqian Wang  Kenichi Nakano  Eri Ito  Hiroshi Kawase  Shinichi Matsushima 《地震工程与结构动力学》2023,52(1):128-146

Under hypothetical and idealized conditions, the horizontal site amplification factor (HSAF) is defined as the ratio of the horizontal Fourier amplitude spectrum (FAS) at a point on the Earth's surface with respect to the horizontal FAS at the identical location but on the outcropping seismological bedrock. The HSAF reflects the profile of local sedimentary soils and weathered rock formations, indicating site effects. In most cases, such an idealized HSAF is difficult to measure directly. Thus, quantitatively estimating a HSAF value is a crucial task in strong-motion prediction over the last century. Fortunately, many strong-motion stations have been constructed throughout Japan, facilitating the characterization of HSAFs down to seismological bedrock at more than 1600 observational sites by the generalized inversion technique (GIT). First, this study reported the similarity distribution of the HSAF and the horizontal-to-vertical spectral ratio of earthquakes (HVSR_E). Subsequently, we proposed a hybrid method from a novel aspect for estimating HSAF in terms of the observed similarity distribution and the vertical amplification correction function (VACF) proposed previously. Compared with the direct use of HVSR_E for substituting HSAF, the hybrid method proposed herein demonstrated an improvement of greater than 30% in terms of the residuals between estimated HSAFs and those separated from observations.  相似文献   

Effects of large-scale wind on the Kuroshio path south of Japan in a 60-year historical OGCM simulation     

Hiroyuki Tsujino  Shiro Nishikawa  Kei Sakamoto  Norihisa Usui  Hideyuki Nakano  Goro Yamanaka 《Climate Dynamics》2013,41(9-10):2287-2318

The effects of large-scale wind forcing on the bimodality of the Kuroshio path south of Japan, the large meander (LM) and non-large meander (NLM), were studied by using a historical simulation (1948–2007) with a high-resolution Ocean general circulation models (OGCM). The Kuroshio in this simulation spent much time in the NLM state, and reproduced several aspects of its long-term path variability for the first time in historical OGCM simulation, presumably because the eddy kinetic energy was kept at a moderate level. By using the simulated fields, the relationships between wind forcing (or Kuroshio transport) and path variation proposed by past studies were tested, and specific roles of eddies in those variations were investigated. The long-term variation of the simulated net Kuroshio transport south of Japan was largely explained by the linear baroclinic Rossby wave adjustment to wind forcing. In the simulated LM events, a triggering meander originated from the interaction of a wind-induced positive sea surface height (SSH) anomaly with the upstream Kuroshio and was enlarged by cyclonic eddies from the recirculation gyre. The cyclonic eddy of the trigger meander was followed by a sizable anticyclonic eddy on the upstream side. Subsequently, a weak (strong) Kuroshio favored the LM (NLM). The LM tended to be maintained when the Kuroshio transport off southern Japan was small, and increasing Kuroshio transport promoted decay of an existing LM. The supply of disturbances from upstream, which is related to the wind-induced SSH variability at low latitudes, contributed to the maintenance of an existing LM.  相似文献   

Simulating present climate of the global ocean–ice system using the Meteorological Research Institute Community Ocean Model (MRI.COM): simulation characteristics and variability in the Pacific sector     

Hiroyuki Tsujino  Mikitoshi Hirabara  Hideyuki Nakano  Tamaki Yasuda  Tatsuo Motoi  Goro Yamanaka 《Journal of Oceanography》2011,67(4):449-479

A long-term spin-up and a subsequent interannual simulation are conducted for the ocean–ice component of the climate model intercomparison project (CMIP)-class earth system model of the Japan Meteorological Agency/Meteorological Research Institute. This experiment has three purposes: first is to assess the ability of our model with the Coordinated Ocean–ice Reference Experiments (COREs) forcing in reproducing the present ocean-climate; second is to understand the ocean-climate variability for the past 60 years; third is to present an example of evaluating an ocean–ice interannual variability simulation. The Pacific Ocean is focused on for the last two purposes. After integrating for about 1500 years with repeated use of a detrended CORE interannual forcing, the model reaches a quasi-steady state where the present climate is reproduced satisfactorily. Then, the interannual variability simulation is conducted with the retrieved forcing trend and the result is analyzed. The simulation is successful at reproducing the long-term variability in the Pacific and surrounding oceans. Brief analyses of the tropical and mid-latitude upper layer, deep circulation, and the Arctic sea ice are presented. A caveat in treating other parts of the globe is due to the recent intense convection in the Southern Ocean caused by a remarkably increasing trend of the Southern Hemisphere westerly. Overall, the current simulation with our CMIP-class ocean–ice model is shown to be useful for studying the present ocean-climate variability, specifically in the Pacific sector. It could also be used as a benchmark control experiment that facilitates further research, model development, and intercomparison.  相似文献   

Role of phase equilibrium in frost heave of fine-grained soil under negligible overburden pressure     

Yoshisuke Nakano  Kaoru Horiguchi 《Advances in water resources》1985,8(2):50-68

The role of the phase equilibrium of water in frost heave was studied for two kinds of soil. The rate of frost heave and the rate of water intake were measured simultaneously under various rates of heat removal. The experimental data revealed a trend common for both soils that the rate of water intake attains its maximum at a certain critical rate of heat removal. The data were analyzed by using equations accurately describing the relation between these rates. The results of the analysis indicate a serious doubt about the validity of phase equilibrium in the system. Alternatively, an assumption was introduced that supercooling occurred between a frost front and an unfrozen part of the soil. It was shown that supercooling could explain the data well under certain conditions.  相似文献   

Role of heat and water transport in frost heaving of fine-grained porous media under negligible overburden pressure     

Yoshisuke Nakano  Kaoru Horiguchi 《Advances in water resources》1984,7(2):93-102

An equation accurately describing the rate of frost heave is derived by using the mixture theory of continuum mechanics. It is shown that the rate of frost heave is determined mainly by the rate of heat removal and the rate of water intake. When the phase equilibrium holds in the system, the relation between the rate of heat removal and the rate of water intake is shown to depend mainly on the phase composition data of a given medium.By studying reported experimental data, it is found that the phase equilibrium may hold until th rate of heat removal reaches a certain critical value. When the rate of heat removal exceeds this critical value, the phase equilibrium may possibly be disrupted for some media.  相似文献   

Seasonal variation in the Ra/Ra ratio of coastal water within the Sea of Japan: Implications for the origin and circulation patterns of the Tsushima Coastal Branch Current     

M. Inoue  K. Tanaka  H. Kofuji  Y. Nakano  K. Komura 《Marine Chemistry》2007,107(4):559-568

In the current study, low-background γ-spectrometry was employed to determine the ²²⁸Ra/²²⁶Ra activity ratio and ¹³⁷Cs activity of 84 coastal water samples collected at six sites along the main island of Japan (Honshu Island) within the Sea of Japan, including the Tsushima Strait, and two other representative sites on Honshu Island (a Pacific shore and the Tsugaru Strait) at 1-month intervals in 2006.The ²²⁸Ra/²²⁶Ra ratio of coastal waters in the Sea of Japan exhibited similar patterns of seasonal variation, with minimum values during early summer (²²⁸Ra/²²⁶Ra = 0.6–0.8), maximum values during autumn (²²⁸Ra/²²⁶Ra = 1.5–3), and a time lag in their temporal changes ( 2.5 months and over  1300 km distance). However, the 2 other sites represented no clear periodic variation.In contrast to the positive correlation between ¹³⁷Cs activity (0.6–1.7 mBq/L) and salinity (15–35), the ²²⁸Ra/²²⁶Ra ratio of coastal water samples from the Sea of Japan was not observed to correlate with salinity, and the increase in the ²²⁸Ra/²²⁶Ra ratio was not as marked (0.5–1; May–June 2004 and 2005) during the migration along Honshu Island. The input of land-derived water and/or the diffusion of radium from coastal sediments is unlikely to have affected the wide seasonal variation in the ²²⁸Ra/²²⁶Ra ratio observed in these water samples.The seasonal variation in the ²²⁸Ra/²²⁶Ra ratio recorded for the coastal waters of the Sea of Japan is considered to be mainly controlled by the remarkable changes in the mixing ratio of the ²²⁸Ra-poor Kuroshio and the ²²⁸Ra-rich continental shelf waters within the East China Sea (ECS). After passing through the Tsushima Strait, this water mass moves northeast along the coastline of the Sea of Japan as the Tsushima Coastal Branch Current (TCBC).  相似文献