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121.
To clarify the generation and dissipation mechanisms of diurnal coastal-trapped waves (CTWs) over the Sakhalin shelf, a series of numerical experiments were conducted using a three-dimensional tidal model of the Okhotsk Sea with density stratification. The tidal model used has good reproduction owing to the careful fitting to the recent observations. The numerical experiments suggested that diurnal CTWs are primarily (~60%) generated by the conversion of tidal energy at the northern corner of the Sakhalin shelf, and further amplified by vorticity generation due to the water column oscillation from Sakhalin Bay and the influence of Kashevarov Bank. From the observations, it was found that diurnal CTWs are effectively dissipated by the strong spin-down due to bottom friction. The conventional turbulent closure model cannot reproduce the observed damping of diurnal CTWs, which raises a caution in modeling the tidal fields in high-latitude regions where diurnal CTWs exist. To resolve this underestimation of the damping, the vertical eddy viscosity was parameterized using its dependence on the observed major axis length of the diurnal tidal current ellipses, which improves the model reproduction on the damping of diurnal CTWs. The model also suggests that the spin-down effects due to friction associated with the sea-ice cover play an important role in the tidal current reduction in the region where diurnal CTWs exist, as the observations suggested. 相似文献
122.
Kazunori Watanabe Koji Ono Keiichi Sakaguchi Akira Takada Hideo Hoshizumi 《Journal of Volcanology and Geothermal Research》1999,89(1-4)
Fugen-dake, the main peak of Unzen Volcano, began a new eruption sequence on November 17, 1990. On May 20, 1991, a new lava dome appeared near the eastern edge of the Fugen-dake summit. Small-scale, 104–106 m3 in volume, Merapi-type block and ash flows were frequently generated from the growing lava dome during May–June, 1991. These pyroclastic flows were accompanied by co-ignimbrite ash plumes that deposited ash-fall deposits downwind of the volcano. Three examples of co-ignimbrite ash-fall deposits from Unzen pyroclastic flows are described. The volume of fall deposits was estimated to be about 30% by volume of the collapsed portions of the dome that formed pyroclastic flows. This proportion is smaller than that described for other larger co-ignimbrite ash-fall deposits from other volcanoes. Grain size distributions of the Unzen co-ignimbrite ash-fall deposits are bi-modal or tri-modal. Most ashes are finer than 4 phi and two modes were observed at around 4–7 phi and 9 phi. They are composed mainly of groundmass fragments. Fractions of another mode at around 2 phi are rich in crystals derived from dome lava. Some of the fine ash component fell as accretionary lapilli from the co-ignimbrite ash cloud indicating either moisture or electrostatic aggregation. We believe that the co-ignimbrite ash of Unzen block and ash flows were formed by the mechanical fracturing of the cooling lava blocks as they collapsed and moved down the slope. These ashes were entrained into the convective plumes generated off the tops of the moving flows. 相似文献
123.
High temperature stability limit of phase egg, AlSiO3(OH) 总被引:1,自引:1,他引:0
Shigeaki Ono 《Contributions to Mineralogy and Petrology》1999,137(1-2):83-89
The stability relations of phase egg, AlSiO3(OH), have been investigated at pressures from 7 to 20 GPa, and temperatures from 900 to 1700 °C in a multi-anvil apparatus.
At the lower pressures phase egg breaks down according to the univariant reaction, phase egg = stishovite + topaz-OH, which
extends from 1100 °C at 11 GPa to 1400 °C at 13 GPa where it terminates at an invariant point involving corundum. At pressures
above the invariant point, the stability of phase egg is limited by the breakdown reaction, phase egg = stishovite + corundum + fluid,
which extends from the invariant point to 1700 °C at 20 GPa. Stishovite crystallized in the Al2O3-SiO2-H2O system contains Al2O3, and the amount of Al2O3 increases with increasing temperature. It is inferred that the Al2O3 content is controlled by the charge-balanced substitution of Si4+ by Al3+ and H+. Aluminum-bearing stishovite coexisting with an H2O-rich fluid may contain a certain amount of water. Therefore, phase egg and stishovite in a subducting slab could transport
some H2O into the deep Earth.
Received: 14 October 1998 / Accepted: 19 May 1999 相似文献
124.
125.
Yoshimitsu Masaki Yasushi Ishigooka Tsuneo Kuwagata Shinkichi Goto Shinji Sawano Toshihiro Hasegawa 《Theoretical and Applied Climatology》2011,106(3-4):383-401
We have studied future changes in the atmospheric and hydrological environments in Northeast Thailand from the viewpoint of risk assessment of future cultural environments in crop fields. To obtain robust and reliable estimation for future climate, ten general circulation models under three warming scenarios, B1, A1B, and A2, were used in this study. The obtained change trends show that daily maximum air temperature and precipitation will increase by 2.6°C and 4.0%, respectively, whereas soil moisture will decrease by c.a. 1% point in volumetric water content at the end of this century under the A1B scenario. Seasonal contrasts in precipitation will intensify: precipitation increases in the rainy season and precipitation decreases in the dry season. Soil moisture will slightly decrease almost throughout the year. Despite a homogeneous increase in the air temperature over Northeast Thailand, a future decrease in soil water content will show a geographically inhomogeneous distribution: Soil will experience a relative larger decrease in wetness at a shallow depth on the Khorat plateau than in the surrounding mountainous area, reflecting vegetation cover and soil texture. The predicted increase in air temperature is relatively consistent between general circulation models. In contrast, relatively large intermodel differences in precipitation, especially in long-term trends, produce unwanted bias errors in the estimation of other hydrological elements, such as soil moisture and evaporation, and cause uncertainties in projection of the agro-climatological environment. Offline hydrological simulation with a wide precipitation range is one strategy to compensate for such uncertainties and to obtain reliable risk assessment of future cultural conditions in rainfed paddy fields in Northeast Thailand. 相似文献
126.
Nakayama K Sei N Handoh IC Shimasaki Y Honjo T Oshima Y 《Marine pollution bulletin》2011,63(5-12):366-369
The effects of polychlorinated biphenyls (PCBs) on liver function and their differences between sexes were analyzed in Japanese medaka (Oryzias latipes) exposed to PCB126 or Kanechlor-400 (KC-400) using microarray. PCB exposure induced vitellogenin 1 expression in female medaka while suppressing choriogenin genes, which suggests that the effects of PCBs on estrogen-responsive genes do not occur directly through an estrogen receptor-mediated pathway. Reduction of androgen receptor alpha expression was also observed, and the gene expression pattern in PCB-exposed males changed to become more similar to that of females. Furthermore, changes in glycolysis-related genes indicate that PCB exposure might enhance glucose production via gluconeogenesis in the liver of medaka. Taken together, our results suggest that PCBs disrupt the endocrine system, especially androgen function, and may have the potential to cause demasculinizing effects. Additionally, induction of gluconeogenesis might be a response to maintain glucose levels consumed as a result of PCB exposures. 相似文献
127.
Thermal effect of the sea breeze on the structure of the boundary layer and the heat budget over land 总被引:2,自引:1,他引:1
The daytime boundary-layer heating process and the air-land heat budget were investigated over the coastal sea-breeze region by means of observations over the Sendai plain in Japan during the summer. In this area, the onset of the sea breeze begins at the coast around 0900 LST, intruding about 35 km inland by late afternoon. The cold sea breeze creates a temperature difference of over 10°C between the coastal and inland areas in the afternoon. On the other hand, warm air advection due to the combination of the counter-sea breeze and land-to-sea synoptic wind occurs in the layer above the cold sea breeze in the coastal region. Owing to this local warm air advection, there is no significant difference in the daytime heating rate over the entire atmospheric boundary layer between the coastal and inland areas. The sensible heat flux from the land surface gradually decreases as distance from the coastline increases, being mainly attributed to the cold sea breeze. The daytime mean cold air advection due to the sea breeze is estimated asQ
adv
local
=–29 W m–2 averaged over the sea breeze region (035 km from the coastline). This value is 17% of the surface sensible heat fluxH over the same region. The results of a two-dimensional numerical model show that the value ofQ
adv
local
/H is strongly affected by the upper-level synoptic wind direction. The absolute value ofQ
adv
local
/H becomes smaller when the synoptic wind has the opposite direction of the sea breeze. This condition occurred during the observations used in the present study. 相似文献
128.
129.
Yasushi Fukamachi Kay I. Ohshima Naoto Ebuchi Tadao Bando Kazuya Ono Minoru Sano 《Journal of Oceanography》2010,66(5):685-696
Time-series data of the vertical structure of the Soya Warm Current (SWC) were obtained by a bottom-mounted acoustic Doppler
current profiler (ADCP) in the middle of the Soya Strait from September 2006 to July 2008. The site of the ADCP measurement
was within the coverage of the ocean-radar measurement around the strait. The volume transport of the SWC through the strait
is estimated on the basis of both the vertical structure observed by the ADCP and the horizontal structure observed by the
radars for the first time. The annual transport estimates are 0.62–0.67 Sv (1 Sv = 106 m3s−1). They are somewhat smaller than the difference between the previous estimates of the inflow and outflow through other straits
in the Sea of Japan, and smaller than those obtained in the region downstream of the strait during 2004–05 (0.94–1.04 Sv).
The difference in the two periods may be attributed to interannual variability of the SWC and/or the different measurement
locations. 相似文献
130.
Steven Emerson Yutaka W. Watanabe Tsuneo Ono Sabine Mecking 《Journal of Oceanography》2004,60(1):139-147
We present a compilation of apparent oxygen utilization (AOU) changes observed in the upper pycnocline of the North Pacific
Ocean over the last several decades. The goal here is to place previously-published data in a common format, and assess the
causes of the observed changes. The general trend along repeat cross sections of the eastern and western subtropical ocean
and the subarctic ocean is an increase in AOU from the mid 1980s to the mid 1990s. AOU has also been increasing in a time-series
study in the northwest subarctic Ocean off of Japan since the late 1960s. Observed AOU changes south of 35°N in the subtropical
ocean are 10–20 μmol kg−1, with much greater changes, reaching 60–80 μmol kg−1 in isolated areas, in the subtropical/subarctic boundary and the subarctic ocean. Analysis of changes in both AOU and salinity
on isopycnals suggests that there are significant salinity-normalized increases that must be due to alteration in the rate
of ventilation or organic matter degradation. A common feature in the data is that the maximum increase in AOU is centered
near the density horizon σθ= 26.6. Time series results from the Oyashio Current region near the winter outcrop area of this density horizon indicate
that surface waters there have become fresher with time, which may mean this density surface has ceased to outcrop in the
latter decades of the 20th century. Whether this is due to natural decadal-scale changes or anthropogenic influences can be
decided by determining future trends in AOU on these density surfaces.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献