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61.
Satellite observations of SSTs have revealed the existence of unstable waves in the equatorial eastern Pacific and Atlantic oceans. These waves have a 20-40-day periodicity with westward phase speeds of 0.4-0.6 m s-1 and wavelengths of 1000-2000 km during boreal summer and fall. They are generally called tropical instability waves (TIWs). This study investigates TIWs simulated by a high-resolution coupled atmosphere-ocean general circulation model (AOGCM). The horizontal resolution of the model is 120 km in... 相似文献
62.
Simulation of state-dependent high-frequency atmospheric variability associated with ENSO 总被引:1,自引:1,他引:0
Jong-Seong Kug K. P. Sooraj Daehyun Kim In-Sik Kang Fei-Fei Jin Yukari N. Takayabu Masahide Kimoto 《Climate Dynamics》2009,32(5):635-648
High-frequency atmospheric variability depends on the phase of El Nino/Southern Oscillation (ENSO). Recently, there is increasing
evidence that state-dependent high-frequency atmospheric variability significantly modulates ENSO characteristics. Hence,
in this study, we examine the model simulations of high-frequency atmospheric variability and, further, its dependency on
the El Nino phase, using atmospheric and coupled GCMs (AGCM and CGCM). We use two versions of physical packages here—with
and without convective momentum transport (CMT)—in both models. We found that the CMT simulation gives rise to a large climatological
zonal wind difference over the Pacific. Also, both the climate models show a significantly improved performance in simulating
the state-dependent noise when the CMT parameterization is implemented. We demonstrate that the better simulation of the state-dependent
noise results from a better representation of anomalous, as well as climatological, zonal wind. Our further comparisons between
the simulations, demonstrates that low-frequency wind is a crucial factor in determining the state-dependency of high-frequency
wind variability. Therefore, it is suggested that the so-called state-dependent noise is directly induced by the low-frequency
wind anomaly, which is caused by SST associated with ENSO. 相似文献
63.
Y. Kawano M. Akiyama T. Ikawa B.P. Roser T. Imaoka J. Ishioka M. Yuhara T. Hamamoto Y. Hayasaka H. Kagami 《Gondwana Research》2006,9(1-2):126
Pre-Cretaceous metasedimentary rocks occurring in the Inner Zone of the Southwest Japan Arc can be divided into three major groups, namely, high P/T metamorphic (Renge and Suo belts), low P/T metamorphic (Hida-Oki, Ryoke and Higo belts), and accretionary terranes (Akiyoshi, Maizuru, Mino-Tamba, and Ashio belts). Major and trace element compositions of most of the sedimentary rocks are typical of relatively mature sedimentary rocks, although abundances of ferromagnesian elements also suggest the presence of a significant mafic to intermediate igneous component. The sedimentary rocks with older Nd model ages (> 2.0 Ga) have high εSr values and major and trace element geochemical signatures typical of mature sediments, whereas those with younger model ages (< 1.45 Ga) have low εSr values and immature geochemical characteristics. With the exception of Hida samples, the sedimentary rocks from other districts have geochemical and isotopic features intermediate between the rocks with old and young Nd model ages. Some of the Hida samples have old Nd model ages, but others are influenced by younger rock fragments and have immature geochemical features. Based on combined isotopic and geochemical evidence, Inner Zone sedimentary rocks with older Nd model ages are interpreted to have been derived from felsic upper continental crustal materials such as Sino-Korean or northwest Yangtze craton granitoids. Compositions of rocks with younger Nd model ages reflect addition of mafic to intermediate detritus, such as island arc basalts and andesites. The rocks with intermediate Nd model ages may have formed in and around the Asian continental margin. The Hida metasedimentary rocks may have been derived from several terranes of varying age and geochemical composition. 相似文献
64.
Masahide Akasaka 《Physics and Chemistry of Minerals》1983,9(5):205-211
Synthetic clinopyroxenes of compositions between CaFe3+AlSiO6 and CaFe 0.85 3+ Ti0.15Al1.15Si0.85O6 have been studied by 57Fe Mössbauer spectroscopy. The spectra consist of two doublets assigned to Fe3+ in M1 and T sites. From the area ratios of the doublets the site occupancies of Fe3+ and Al were determined. Si decreases from 1.00 to 0.85 and Al+Fe3+ increases from 1.00 to 1.15 per formula unit with increasing CaTiAl2O6 component of the clinopyroxene. The atomic ratio of Fe3+(T)/Fe3+(total) is 0.11–0.16; 4.5–7.5 percent of the T sites are occupied by Fe3+. Thus the presence of Si-O-Fe3+, Al-O-Fe3+, and Fe3+-O-Fe3+ bonds is expected in addition to Si-O-Si, Si-O-Al and Al-O-Al bonds. However, the possibility of the former bonds being present would be small, because the amount of Fe3+(T) is far less than that of Si and Al. The isomer shift of Fe3+(T) is one of the largest in the values found previously for Fe3+(T) in silicates. It increases with increasing CaTiAl2O6 component and seems to be correlated to the ionic character of the cation — anion bonds calculated from electronegativity. The quadrupole splittings of Fe3+(M1) and Fe3+(T) decrease with the substitution of Fe3+?Ti4+ in the M1 and of Si?Al in the T sites. 相似文献
65.
A study of the dynamic response of offshore structures to simultaneous loadings by random earthquake ground motions and random sea waves is presented. Emphasis is placed on the evaluation of dynamic soil-structure interaction effects and also on the evaluation of non-linear hydrodynamic damping effects due to sea waves for the seismic response. The structure is discretized using the finite element method. Sea waves are represented by Bretschneider's power spectrum and the Morison equation defines the wave forcing function. The Tajimi-Kanai power spectrum is used for the horizontal ground acceleration due to earthquakes. The governing equations of motion are obtained by the substructure method. Response analysis is carried out using the frequency-domain random vibration approach. It is found that the first few vibrational modes contribute significantly to the dynamic response. The response due to earthquake loadings is larger when the soil-structure interaction effects are considered. The hydrodynamic damping forces are higher in random seas than in still water and sea waves reduce the seismic response of offshore structures. Studies on the first passage probabilities of response indicate that small sea waves enhance the reliability of offshore structures against earthquake forces. 相似文献
66.
67.
The northeastern Japan forms a typical arcuate structure with a remarkable zonal arrangement of many geologic features, including the distribution of Quaternary volcanoes. Thus two distinct zones of volcanoes are noted here: i. e., Nasu zone on the east and Tyokai zone on the west. Some of the volcanoes of Nasu zone are characterized by the presence of pumice flows or pumice falls, sometimes of very large scales. These pumice flows belong to the calc-alkali rock series. While pumice flows or falls are rare in the Tyokai zone, where they are present though on small scale. Migration of the center of activity is noted along linear fissures, running either from east to west, or north to south at some volcanoes of Nasu zone, and consequently large swarms of volcanoes are common in this zone. While central eruption with definite center is typical of the Tyokai zone. From the petrographical and petrochemical study on the lavas and pyroclastics the original magma of the Nasu zone is estimated to be tholeiitic, and that of the Tyokai zone high-alumina basaltic. Abundant calc-alkali rocks are derived from these parental magmas. Thus the difference in the volcanic activity should be ascribed to the different nature of the parental magmas or the magmas derived from them. 相似文献
68.
Masahide Wakita Makio C. Honda Kazuhiko Matsumoto Tetsuichi Fujiki Hajime Kawakami Sayaka Yasunaka Yoshikazu Sasai Chiho Sukigara Mario Uchimiya Minoru Kitamura Toru Kobari Yoshihisa Mino Akira Nagano Shuichi Watanabe Toshiro Saino 《Journal of Oceanography》2016,72(5):665-685
The annual flux of biologically produced organic carbon from surface waters is equivalent to annual net community production (NCP) at a steady state and equals the export of particulate and dissolved organic carbon (POC and DOC, respectively) to the ocean interior. NCP was estimated from carbon budgets of salinity-normalized dissolved inorganic carbon (nDIC) inventories at two time-series stations in the western subarctic (K2) and subtropical (S1) North Pacific Ocean. By using quasi-monthly biogeochemical observations from 2004 to 2013, monthly mean nDIC inventories were integrated from the surface to the annual maximum mixed layer depth and corrected for changes due to net air–sea CO2 exchange, net CaCO3 production, vertical diffusion from the upper thermocline, and horizontal advection. The annual organic carbon flux at K2 (1.49 ± 0.42 mol m?2 year?1) was lower than S1 (2.81 ± 0.53 mol m?2 year?1) (p < 0.001 based on t test). These fluxes consist of three components: vertically exported POC fluxes (K2: 1.43 mol m?2 year?1; S1: 2.49 mol m?2 year?1), vertical diffusive DOC fluxes (K2: 0.03 mol m?2 year?1; S1: 0.25 mol m?2 year?1), and suspended POC fluxes (K2: 0.03 mol m?2 year?1; S1: 0.07 mol m?2 year?1). The estimated POC export flux at K2 was comparable to the sum of the POC flux observed with drifting sediment traps and active carbon flux exported by migrating zooplankton. The export fluxes at both stations were higher than those reported at other time-series sites (ALOHA, the Bermuda Atlantic Time-series Study, and Ocean Station Papa). 相似文献
69.
Makio C. Honda Hajime Kawakami Kazuhiko Matsumoto Masahide Wakita Tetsuichi Fujiki Yoshihisa Mino Chiho Sukigara Toru Kobari Mario Uchimiya Ryo Kaneko Toshiro Saino 《Journal of Oceanography》2016,72(3):373-386
Drifting sediment trap experiments were conducted during various seasons to elucidate the characteristics of particles sinking through the upper 200 m of the water column in the western Pacific at subarctic station K2 and subtropical station S1. The sinking particle flux increased when primary productivity was high at each station, during June–July at K2 and during February at S1. Biogenic opal (Opal) and CaCO3 were the major components of the fluxes at K2 and S1, respectively. Contrary to the expectation of a high flux at the eutrophic station K2 and low flux at the oligotrophic station S1, the annual average organic carbon fluxes at 100 m were comparable at both stations: 62.7 mg C m?2 day?1 at K2 and 56.1 mg C m?2 day?1 at S1. The similarity of the fluxes was perhaps a reflection of the unexpectedly high primary production at S1. At K2, the organic carbon export ratio (organic carbon flux/primary productivity) was significantly and negatively correlated with primary production and tended to decrease with depth. The magnitude of the rate of attenuation of the organic carbon flux with depth was larger at S1 than at K2. This rate of attenuation tended to decrease and increase with primary production at K2 and S1, respectively. The explanation for these patterns may be that the flux of labile organic carbon at relatively shallow depths decreased with increasing primary production at K2, and zooplankton grazing pressure increased with increasing primary productivity at S1. 相似文献
70.
Insight into nitrous oxide production processes in the western North Pacific based on a marine ecosystem isotopomer model 总被引:2,自引:0,他引:2