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31.
Peng K. Hong Hiroko Miyahara Yusuke Yokoyama Yukihiro Takahashi Mitsuteru Sato 《Journal of Atmospheric and Solar》2011,73(5-6):587-591
We examined the effect of the 11-year solar cycle and quasi-biennial oscillation (QBO) on the ～27-day solar rotational period detected in tropical convective cloud activity. We analyzed the data of outgoing longwave radiation (OLR) for AD1979–2004, dividing into four different cases by the combination of high and low solar activities in terms of the 11-year variation, and easterly and westerly stratospheric winds associated with QBO. As a result, ～27-day variation has been most significantly detected in high solar activity period around the Indo-Pacific Warm Pool. Based on correlation analysis, we find that solar rotation signal can explain 10–20% of OLR variability around the tropical warm pool region during the high solar activity period. The spatial distribution has been, however, apparently different according to the phases of QBO. It is suggested that the 11-year solar cycle and stratospheric QBO have a possibility to cause large-scale oceanic dipole phenomena. 相似文献
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Hitoshi Mikada Kyohiko Mitsuzawa Hiroyuki Matsumoto Tomoki Watanabe Shigehiko Morita Riyo Otsuka Hiroko Sugioka Toshitaka Baba Eiichiro Araki Kiyoshi Suyehiro 《Tectonophysics》2006,426(1-2):95
At the 2003 Tokachi-oki earthquake of M8, seafloor phenomena such as a generation process of tsunami, seafloor uplifts, turbidity current, etc., were observed using a cabled observatory installed on the seafloor. The turbidity current was observed as a benthic storm caused presumably by the mainshock. The seafloor uplifts were observed at the mainshock and continuously after the mainshock. The uplifts were 0.35, 0.37, and 0.12 m for epicentral distances of 25.5, 31.4, and 81.7 km, respectively. After the mainshock, a continuous uplift of the seafloor is observed at all three pressure gauge locations indicating that there was a change in the state of friction on the plate boundary interface by the mainshock. In this paper, we first show what was observed using the cabled observatory installed right above the focal area of the earthquake, and then we discuss to summarize these phenomena associated with the earthquake, its possible causes, and future directions in long term monitoring of seismogenic processes. 相似文献
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In order to understand the origin of iron-rich olivine in the matrices of type 3 ordinary chondrites, the reaction of metallic iron and enstatite, with and without forsterite and SiO2, has been experimentally reproduced at temperatures between 1150° and 800°C and PO2 between 10−11 and 10−16 atm (between the IQF and MW buffers). The olivine produced ranges from Fo58 to Fo34 and this composition does not change significantly with temperature and time of the runs. The magnesian olivine which forms does become more magnesian with increasing forsterite/enstatite ratio of the starting materials. Iron-rich olivine (Fo< 35) cannot be formed by the reaction of enstatite and metallic iron, with or without forsterite as starting materials but it can be formed in the presence of free silica. The composition of olivine becomes more iron-rich with increasing silica/enstatite ratio. The compositional range of olivine formed from each mixture is 25–30 mole% Fo regardless of the temperature, composition, mineral assemblage, and run duration.From these experimental results, two possibilities suggested for the origin of the iron-rich olivine in the matrices of type 3 ordinary chondrites: (1) free silica must have been present if the iron-rich olivine was formed by solid-state reactions under oxidizing condition in the solar nebula; (2) reaction of silicon-rich gas with metallic iron took place under oxidizing condition in the solar nebula. Though it is difficult to define which alternative was dominant, the formation of free silica or silicon-rich gas may be a result of fractional condensation. This is possible if there is a reaction relation between forsterite and gas to produce enstatite. The suggested fractional condensation is supported by the fact that the compositions of the fine-grained matrices of type 3 ordinary chondrites are more silica-rich than the bulk compositions of the chondrites. Though it is not known whether such conditions were established all over the nebula or locally in the nebula, both fractionation and more oxidizing conditions than the average solar nebula are required for the formation of matrix olivine. 相似文献
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A new type of pycnostad has been identified in the western subtropical-subarctic transition region of the North Pacific, based
on the intensive hydrographic survey carried out in July, 2002. The potential density, temperature and salinity of the pycnostad
were found to be 26.5–26.7 σ
θ
, 5°–7°C and 33.5–33.9 psu respectively. The pycnostad is denser, colder and fresher than those of the North Pacific Central
Mode Water and different from those of other known mode waters in the North Pacific. The thickness of the pycnostad is comparable
to that of other mode waters, spreading over an area of at least 650 × 500 km around 43°N and 160°E in the western transition
region. Hence, we refer to the pycnostad as Transition Region Mode Water (TRMW). Oxygen data, geostrophic current speed and
climatology of mixed layer depth in the winter suggest that the TRMW is formed regularly in the deep winter mixed layer near
the region where it was observed. Analysis of surface heat flux also supports the idea and suggests that there is significant
interannual variability in the property of the TRMW. The TRMW is consistently distributed between the Subarctic Boundary and
the Subarctic Front. It is also characterized by a wide T-S range with similar density, which is the characteristic of such
a transition region between subtropical and subarctic water masses, which forms a density-compensating temperature and salinity
front. The frontal nature also tends to cause isopycnal intrusions within the pycnostad of the TRMW. 相似文献
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Emily L. Kara Chad Heimerl Tess Killpack Matthew C. Van de Bogert Hiroko Yoshida Stephen R. Carpenter 《Aquatic Sciences - Research Across Boundaries》2012,74(2):241-253
A phosphorus (P) budget was estimated for the watershed of Lake Mendota, Wisconsin, to assess the effects of nutrient management
on P accumulation in the watershed soils. We estimated how nutrient management programs and legislation have affected the
budget by comparing the budget for 2007 to a budget calculated for 1995, prior to implementation of the programs. Since 1995,
inputs decreased from 1,310,000 to 853,000 kg P/yr (35% reduction) and accumulation decreased from 575,000 to 279,000 kg P/yr
(51% reduction). Changes in P input and accumulation were attributed primarily to enhanced agricultural nutrient management,
reduction in dairy cattle feed supplements and an urban P fertilizer ban. Four scenarios were investigated to determine potential
impacts of additional nutrient management tactics on the watershed P budget and P loading to Lake Mendota. Elimination of
chemical P fertilizer input has the greatest potential to reduce watershed P accumulation and establishment of riparian buffers
has the greatest potential to prevent P loading to Lake Mendota. 相似文献
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The annual subduction rate of the North Pacific was calculated based on isopycnally averaged hydrographic climatology (HydroBase), high-resolution winter mixed-layer climatology (NWMLC), and various wind stress climatologies from ship reports, numerical weather prediction products, and satellite products. The calculation was performed using Lagrangian coordinates in the same manner as in previous works, except a less smoothed oceanic climatology (HydroBase and NWMLC) was used instead of a World Ocean Atlas. Differences in the wind stress climatologies have very little effect on subduction rate estimates. The subduction rate census for density classes showed peaks corresponding to subtropical mode water (STMW), central mode water (CMW), and eastern subtropical mode water (ESTMW). The deeper mixed layer and the associated sharper mixed-layer fronts in the present climatology resulted in a larger lateral induction, which boosted the subduction rate, especially for the potential density anomaly (σθ) range of the lighter STMW (25.0 < σθ < 25.2 kg m−3) and lighter CMW (26.0 < σθ < 26.2 kg m−3), compared to previous estimates. The renewal time of permanent pycnocline water was estimated as the volume of water divided by the subduction rate for each σθ class: 2–4 years for ESTMW (24.5 < σθ < 25.2 kg m−3), 2 years for the lighter STMW (25.0 < σθ < 25.3 kg m−3), 5–9 years for the denser STMW (25.3 < σθ < 25.6 kg m−3), 10–20 years for the lighter CMW (26.0 < σθ < 26.2 kg m−3), 20–30 years for the middle CMW (26.2 < σθ < 26.3 kg m−3), and 60 years or longer for the denser CMW (26.3 < σθ < 26.6 kg m−3). A comparison of the water volume and subduction rate in potential temperature–salinity (θ–S) space indicated that the upper permanent pycnocline water (25.0 < σθ < 26.2 kg m−3) was directly maintained by nondiffusive subduction of winter surface water, including STMW and lighter CMW. The lower permanent pycnocline water (26.2 < σθ < 26.6 kg m−3) may be maintained through the subduction of fresher and colder water from the subarctic–subtropical transition region and subsequent mixing with saltier and warmer water. Diagnosis of the potential vorticity (PV) of the subducted water demonstrated that the low PV of STMW was mainly due to the large subduction rate, whereas that of both ESTMW and CMW was due mainly to the small density advection rate (cross-isopycnal flow). Additionally, a relatively large subduction rate probably contributes to the low PV of part of the lighter CMW (ESTMW) formed in the region around 38°N and 170°W (28°N and 145°W), which is characterized by a relatively thick winter mixed layer and an associated mixed-layer front, causing a large lateral induction rate. 相似文献
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Shingo Kato Kurt Hara Hiroko Kasai Takashi Teramura Michinari Sunamura Jun-ichiro Ishibashi Takeshi Kakegawa Toshiro Yamanaka Hiroyuki Kimura Katsumi Marumo Tetsuro Urabe Akihiko Yamagishi 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1844-1855
Spatial distribution, diversity, and composition of bacterial communities within the shallow sub-seafloor at the deep-sea hydrothermal field of the Suiyo Seamount, Izu-Bonin Arc, Western Pacific Ocean, were investigated. Fluids were sampled from four boreholes in this area. Each borehole was located near or away from active vents, the distance ranging 2–40 m from active vents. In addition, fluids discharging from a natural vent and ambient seawater were sampled in this area. We extracted DNA from each sample, amplified bacterial 16S rRNA genes by PCR, cloned the PCR products and sequenced. The total number of clones analyzed was 348. Most of the detected phylotypes were affiliated with the phylum Proteobacteria, of which the detection frequency in each clone library ranged from 84.6% to 100%. The bacterial community diversity and composition were different between hydrothermal fluids and seawater, between fluids from the boreholes and the vent, and even among fluids from each borehole. The relative abundances of the phylotypes related to Thiomicrospira, Methylobacterium and Sphingomonas were significantly different among fluids from each borehole. The phylotypes related to Thiomicrospira and Alcanivorax were detected in all of the boreholes and vent samples. Our findings provide insights into bacterial communities in the shallow sub-seafloor environments at active deep-sea hydrothermal vent fields. 相似文献
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The parameters of the magnetic flux distribution inside low-latitude coronal holes (CHs) were analyzed. A statistical study of 44 CHs based on Solar and Heliospheric Observatory (SOHO)/MDI full disk magnetograms and SOHO/EIT 284?Å images showed that the density of the net magnetic flux, B net, does not correlate with the associated solar wind speeds, V x . Both the area and net flux of CHs correlate with the solar wind speed and the corresponding spatial Pearson correlation coefficients are 0.75 and 0.71, respectively. A possible explanation for the low correlation between B net and V x is proposed. The observed non-correlation might be rooted in the structural complexity of the magnetic field. As a measure of the complexity of the magnetic field, the filling factor, f(r), was calculated as a function of spatial scales. In CHs, f(r) was found to be nearly constant at scales above 2 Mm, which indicates a monofractal structural organization and smooth temporal evolution. The magnitude of the filling factor is 0.04 from the Hinode SOT/SP data and 0.07 from the MDI/HR data. The Hinode data show that at scales smaller than 2 Mm, the filling factor decreases rapidly, which means a multifractal structure and highly intermittent, burst-like energy release regime. The absence of the necessary complexity in CH magnetic fields at scales above 2 Mm seems to be the most plausible reason why the net magnetic flux density does not seem to be related to the solar wind speed: the energy release dynamics, needed for solar wind acceleration, appears to occur at small scales below 1 Mm. 相似文献