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1.
Costijn Zwart Niels C. Munksgaard Alain Protat Naoyuki Kurita Dionisia Lambrinidis Michael I. Bird 《水文研究》2018,32(15):2296-2303
This work provides a comprehensive physically based framework for the interpretation of the north Australian rainfall stable isotope record (δ18O and δ2H). Until now, interpretations mainly relied on statistical relationships between rainfall amount and isotopic values on monthly timescales. Here, we use multiseason daily rainfall stable isotope and high resolution (10 min) ground‐based C‐band polarimetric radar data and show that the five weather types (monsoon regimes) that constitute the Australian wet season each have a characteristic isotope ratio. The data suggest that this is not only due to changes in regional rainfall amount during these regimes but, more importantly, is due to different rain and cloud types that are associated with the large scale circulation regimes. Negative (positive) isotope anomalies occurred when stratiform rainfall fractions were large (small) and the horizontal extent of raining areas were largest (smallest). Intense, yet isolated, convective conditions were associated with enriched isotope values whereas more depleted isotope values were observed when convection was widespread but less intense. This means that isotopic proxy records may record the frequency of which these typical wet season regimes occur. Positive anomalies in paleoclimatic records are most likely associated with periods where continental convection dominates and convection is sea‐breeze forced. Negative anomalies may be interpreted as periods when the monsoon trough is active, convection is of the oceanic type, less electric, and stratiform areas are wide spread. This connection between variability of rainfall isotope anomalies and the intrinsic properties of convection and its large‐scale environment has important implications for all fields of research that use rainfall stable isotopes. 相似文献
2.
Jiro Yoshida Hideo Sudo Masaji Matsuyama Yoshihiro Kurita Yuji Mine 《Journal of Oceanography》1993,49(1):121-129
A comparison between Japan-equator XBT sections along 150°E in late November 1989 and along 140°E in early December 1991 is made. The warmest surface water above 29°C diminished to the south of 2–4°N and the surface mixed layer noticeably decreased in thickness in the equatorial region in December 1991; besides, the North Equatorial Countercurrent was intensified. This is considered to be a manifestation of changes in the surface layer of the western equatorial Pacific in the mature phase of El Niño. 相似文献
3.
Abstract A controversial stratigraphic section, the Taneichi Formation, is exposed along the Pacific Coast of northeastern Honshu, the main island of the Japanese Archipelago. Although most sediments of the formation have long been dated as late Cretaceous, the northern section of it has been assigned to (i) the Upper Cretaceous; (ii) the Paleogene; or (iii) the Neogene. In the present report, we present the data of palynological and sedimentological studies, showing that the northern section should be assigned to the Neogene. A more important point in the present study is that we invoke some basic principles of fluvial sedimentology to resolve this stratigraphic subject. The lignite layers full of Paleogene–Miocene dinoflagellate cysts and pollen assemblages drape over the boulder‐sized (>40 cm in diameter) clasts in the northern section. However, the layers totally consist of aggregates of small lignite chips, indicating that the lignites are allochthonous materials. The mega‐clasts with derived microfossils in the lignites are thought to have been deposited as Neogene fluvial (flood) sediments in the newly formed Japanese Archipelago. Prior to the Miocene, the northern Honshu was part of the Eurasian Plate, thus the boulder‐sized clasts cannot be envisaged as long river flood deposits along the continental Paleogene Pacific Coast. Instead, the mega‐clasts with the draping lignites were probably derived from nearby Miocene highlands in the newly born island arc. 相似文献
4.
Hiroshi Taura Hisayoshi Yurimoto Kei Kurita Shigeho Sueno 《Physics and Chemistry of Minerals》1998,25(7):469-484
Partition coefficients between olivine and melt at upper mantle conditions, 3 to 14 GPa, have been determined for 27 trace
elements (Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Cs, Ba, La and Ce) using
secondary-ion mass-spectrometry (SIMS) and electron-probe microanalysis (EPMA). The general pattern of olivine/melt partitioning
on Onuma diagrams resembles those reported previously for natural systems. This agreement strongly supports the argument that
partitioning is under structural control of olivine even at high pressure. The partition coefficients for mono- and tri-valent
cations show significant pressure dependence, both becoming larger with pressure, and are strongly correlated with coupled
substitution into cation sites in the olivine structure. The dominant type of trace element substitution for mono- and tri-valent
cations into olivine changes gradually from (Si, Mg)↔(Al, Cr) at low pressure to (Si, Mg)↔(Al, Al) and (Mg, Mg)↔(Na, Al) at
high pressure. The change in substitution type results in an increase in partition coefficients of Al and Na with pressure.
An inverse correlation between the partition coefficients for divalent cations and pressure has been observed, especially
for Ni, Co and Fe. The order of decreasing rate of partition coefficient with pressure correlates to strength of crystal field
effect of the cation. The pressure dependence of olivine/melt partitioning can be attributed to the compression of cation
polyhedra induced by pressure and the compensation of electrostatic valence by cation substitution.
Received: March 6, 1997 / Revised, accepted: March 12, 1998 相似文献
5.
Tuneto Kurita 《Physics of the Earth and Planetary Interiors》1974,8(2):177-201
The upper-mantle structure down to about 220 km in the central United States has been inferred from long-period P- and S-wave spectra of deep earthquakes recorded at three WWSSN stations, by using the re-formulated transfer ratio method. This method has been experimentally shown to be a very powerful means for elucidating the fine configuration of the low-velocity zone. The strong advantage of this method is its ability to determine separately the extent of the velocity decrease and the depth to the bottom of this zone, which is more uncertain by the other methods.From the Interior Plain to the Gulf of Mexico the low-velocity zone shifts to a shallower depth while increasing its thickness and decreasing its velocities. This zone is made up of an approx. 50 km thick layer ranging in depth from about 150 to 200 km under the Interior Plain, an approx. 75 km thick layer from about 120 to 195 km under the Gulf Coastal Plain, and an approx. 80 km thick layer from about 95 to 175 km under the continental shelf of the Gulf of Mexico, all nearly along 89°N longitude. The decrease in S-wave velocity at the top of this zone is about 0.30, 0.45, and 0.70 km/sec under each of the above areas, although the last value may be somewhat an overestimate. Both boundaries of this zone are sharp, the transition occurring over at most ca. 10 km. In this region the existence of the high-velocity lid zone is possible. 相似文献
6.
Aleksey S. Telyakovskiy Gastão A. Braga Satoko Kurita Jeff Mortensen 《Advances in water resources》2010
For certain initial and boundary conditions the Boussinesq equation, a nonlinear partial differential equation describing the flow of water in unconfined aquifers, can be reduced to a boundary value problem for a nonlinear ordinary differential equation. Using Song et al.'s (2007) [7] approach, we show that for zero head initial condition and power-law flux boundary condition at the inlet boundary, the solution in the form of power series can be obtained with Barenblatt's (1990) [2] rescaling procedure applied to the power series solution obtained in Song et al. (2007) [7] for the power-law head boundary condition. Polynomial approximations can then be obtained by taking terms from the power series. Although for a small number of terms the newly obtained approximations may be worse than polynomial approximations obtained by other techniques, any desired accuracy can be achieved by taking more terms from the power series. 相似文献
7.
Phytoplankton distribution and its relationship to water masses were investigated in the East China Sea from February 15 to March 10, 1993. Diatoms, dinoflagellates and coccolithophorids were examined by the Utermöhl method. Two distinct phytoplankton assemblages were identified: a shelf and oceanic assemblage. The shelf community was characterized by a high abundance of diatoms, particularly, a benthic diatomParalia sulcata, and the oceanic community by numerical dominance of coccolithophorids and occurrence of surface warm-water species of diatoms. A boundary of both communities was located at the shelf edge that coincided with the shelf side of a Kuroshio front.P. sulcata was the most dominant in the inner shelf area throughout the water column. The occurrence of this species near the surface was considered to be a good indicator of the enhanced vertical mixing driven by winter monsoon. The species survives under extremely low light intensity near the bottom during the stratified periods in summer. During the winter time when light condition at the bottom becomes most unfavorable, resuspension and upward traveling of the species due to enhanced vertical mixing seem to be advantageous to acquire suitable light condition. Because of its predominance, possible importance ofP. sulcata is suggested in material cycling on the shelf, particularly near the bottom. 相似文献
8.
Kurt Leinenweber Wataru Utsumi Yoshihiko Tsuchida Takehiko Yagi Kei Kurita 《Physics and Chemistry of Minerals》1991,18(4):244-250
New high-pressure orthorhombic (GdFeO3-type) perovskite polymorphs of MnSnO3 and FeTiO3 have been observed using in situ powder X-ray diffraction in a diamond-anvil cell with synchrotron radiation. The materials are produced by the compression of the lithium niobate polymorphs of MnSnO3 and FeTiO3 at room temperature. The lithium niobate to perovskite transition occurs reversibly at 7 GPa in MnSnO3, with a volume change of -1.5%, and at 16 GPa in FeTiO3, with a volume change of -2.8%. Both transitions show hysteresis at room temperature. For MnSnO3 perovskite at 7.35 (8) GPa, the orthorhombic cell parameters are a=5.301 (2) A, b=5.445 (2) Å, c=7.690 (8) Å and V= 221.99 (15) Å3. Volume compression data were collected between 7 and 20 GPa. The bulk modulus calculated from the compression data is 257 (18) GPa in this pressure region. For FeTiO3 perovskite at 18.0 (5) GPa, cell parameters are a=5.022 (6) Å, b=5.169 (5) Å, c=7.239 (9) Å and V= 187.94 (36) Å3. Based on published data on the quench phases, the FeTiO3 perovskite breaks down to a rocksalt + baddelyite mixture of FeO and TiO2 at 23 GPa. This is the first experimental verification of the pressure-induced breakdown of a perovskite to simple oxides. 相似文献
9.
Tuneto Kurita 《Physics of the Earth and Planetary Interiors》1976,13(1):18-36
The directivity function method is combined with an earthquake sequence study to obtain the reliable estimates of rupture area and rupture velocity of two right-lateral strike-slip earthquakes occurring along the San Andreas fault zone in central California. By utilizing a significant difference in velocity structure on both sides of the main fault, a modified version of the directivity function is formulated and applied to near-field SH waves. On assuming aftershock areas following their step-wise increase with time as rupture areas, an extensive systematic search for the best fit between the observed and theoretical directivity functions is made for a combination of both source parameters. The rupture at the February 24, 1972 earthquake (ML = 5.0) propagated unilaterally with an average velocity of about 2.3 km/sec. It produced a rectangular area, the horizontal and vertical lengths being about 5 and 2 km, respectively. The rupture at the September 4, 1972 earthquake (ML = 4.6) was of bilateral, yielding a nearly square rupture area of which side length is about 2 km. The rupture velocity of this earthquake, though some ambiguities resulting from a lower quality of the observed directivity function, is estimated at 1.9 km/sec or less. A difference in average rupture velocity between both earthquakes might imply its dependence on the ambient tectonic environment such as represented by local stress and humidity. By taking into account a post-earthquake creep increase of about 3.0–3.5 cm observed at a creepmeter station situated over the focus of the February 24, 1972 earthquake, its stress drop and seismic moment are estimated at about 10 bar and 1023 dyn · cm, respectively. The above procedure has a broad applicability for recovering reliable estimates of source parameters, especially when it is combined with a synthetic approach. 相似文献
10.
We studied degassing of He and Ar from granite, basalt and volcanic tuff samples which were subjected to uniaxial compression. From the samples which were fractured in the dilatant region He was always degassed, while degassing of Ar dependent not only on the dilatancy, but also on the type of rock and the compressional conditions such as wet, room dry or vacuum conditions. It is concluded that degassing of rare gases from the compressed samples depends primarily on the generation of new surface area by dilatancy. 相似文献