Concentrations of metallic elements in long-range-transported aerosols measured simultaneously at three coastal sites in China and Japan     

Kojiro?ShimadaEmail author  Xiaoyang?Yang  Yushi?Araki  Ayako?Yoshino  Akinori?Takami  Xuan?Chen  Fan?Meng  Shiro?Hatakeyama 《Journal of Atmospheric Chemistry》2018,75(2):123-139

To determine the effects of long-range transport of aerosols from an upwind area in East Asia to a downwind area in Japan, we chemically analyzed aerosols collected simultaneously on Tuoji Island (Shandong Province, China), Fukue Island (Nagasaki Prefecture, Japan), and Cape Hedo (Okinawa Prefecture, Japan). We focused on changes in the metallic composition of PM_2.5 aerosols during long-range transport. The average mass concentrations of PM_2.5 at the three sites decreased in the order Tuoji Island > Fukue Island ≈ Cape Hedo (48.3 ± 4.5, 13.9 ± 1.5, and 13.2 ± 0.9 μg/m³, respectively). The fraction of coarse particles in total suspended particles estimated by (1–PM_2.5/TSP) was highest on Cape Hedo, indicating that the contribution of sea salts was increased by long-range transport of the aerosols over the ocean. Enrichment factor analysis revealed that at all three sites, Al, K, Ca, Mn, Fe, Co, Sr, and Ba originated from soil; whereas Cr, Ni, Cu, Zn, As, Mo, Ag, Cd, Sn, Sb, Tl, and P appeared to be of anthropogenic origin. Na was the most abundant element on Cape Hedo, indicating the addition of sea salts during aerosol transport. The V concentration was highest at Fukue Island, which was ascribed to V emission from ships. Sixty-one percent of the V on Fukue Island and 62% of the V on Cape Hedo were determined to have originated from ships, implicating of data obtained on dates during which backward trajectory analysis indicated that the same air mass passed over Tuoji Island, Fukue Island, and Cape Hedo in that order.  相似文献   

The anisotropy of cosmic ray arrival directions around 10 eV     

N. Hayashida  M. Nagano  D. Nishikawa  H. Ohoka  N. Sakaki  M. Sasaki  M. Takeda  M. Teshima  R. Torii  T. Yamamoto  S. Yoshida  K. Honda  N. Kawasumi  I. Tsushima  N. Inoue  E. Kusano  K. Shinozaki  N. Souma  K. Kadota  F. Kakimoto  K. Kamata  S. Kawaguchi  Y. Kawasaki  H. Kitamura  Y. Matsubara  K. Murakami  Y. Uchihori  H. Yoshii 《Astroparticle Physics》1999,10(4):125-311

Anisotropy in the arrival directions of cosmic rays with energies above 10¹⁷ eV is studied using data from the Akeno 20 km² array and the Akeno Giant Air Shower Array (AGASA), using a total of about 114 000 showers observed over 11 years. In the first harmonic analysis, we have found a strong anisotropy of 4% around 10¹⁸ eV, corresponding to a chance probability of 0.2% after taking the number of independent trials into account. with two-dimensional analysis in right ascension and declination, this anisotropy is interpreted as an excess of showers near the directions of the Galactic Center and the Cygnus region.  相似文献   

Interdecadal Variations of ENSO Signals and Annual Cycles Revealed by Wavelet Analysis     

Takashi Setoh  Shiro Imawaki  Alexander Ostrovskii  Shin-Ichiro Umatani 《Journal of Oceanography》1999,55(3):385-394

Interdecadal variations of El Niño/Southern Oscillation (ENSO) signals and annual cycles appearing in the sea surface temperature (SST) and zonal wind in the equatorial Pacific during 1950–1997 are studied by wavelet, empirical orthogonal function (EOF) and singular value decomposition (SVD) analyses. The typical timescale of ENSO is estimated to be about 40 months before the late 1970s and 48–52 months after that; the timescale increased by about 10 months. The spatial pattern of the ENSO signal appearing in SST also changed in the 1970s; before that, the area of strong signal spread over the extratropical regions, while it is confined near the equator after that. The center of the strongest signal shifted from the central and eastern equatorial Pacific to the South American coast at that time. These SST fluctuations near the equator are associated with fluctuations of zonal wiond, whose spatial pattern also shifted considerably eastward at that time. In the eastern equatorial Pacific, amplitudes of annual cycles of SST are weak in El Niño years and strong in La Niña years. This relation is not clear, however, in the 1980s and 1990s.  相似文献   

Mixed layer depth front and subduction of low potential vorticity water under seasonal forcings in an idealized OGCM     

Shiro Nishikawa  Atsushi Kubokawa 《Journal of Oceanography》2012,68(1):53-62

The mixed layer depth (MLD) front and subduction under seasonal variability are investigated using an idealized ocean general circulation model (OGCM) with simple seasonal forcings. A sharp MLD front develops and subduction occurs at the front from late winter to early spring. The position of the MLD front agrees with the curve where \({\rm D}T_{\rm s}/{\rm D}t = \partial T_{\rm s} /\partial t + {\user2{u}}_{\rm g} \cdot \nabla T_{\rm s} = 0\) is satisfied (t is time, \({\user2{u}}_{\rm g}\) is the upper-ocean geostrophic velocity, \(T_{\rm s}\) is the sea surface temperature (SST), and \(\nabla\) is the horizontal gradient operator), indicating that thick mixed-layer water is subducted there parallel to the SST contour. This is a generalization of the past result that the MLD front coincides with the curve \({\user2{u}}_{\rm g} \cdot \nabla T_{\rm s} = 0\) when the forcing is steady. Irreversible subduction at the MLD front is limited to about 1 month, where the beginning of the irreversible subduction period agrees with the first coincidence of the MLD front and \({\rm D}T_{\rm s}/{\rm D}t =0\) in late winter, and the end of the period roughly corresponds to the disappearance of the MLD front in early spring. Subduction volume at the MLD front during this period is similar to that during 1 year in the steady-forcing model. Since the cooling of the deep mixed-layer water occurs only in winter and SST can not fully catch up with the seasonally varying reference temperature of restoring, the cooling rate of SST is reduced and the zonal gradient of the SST in the northwestern subtropical gyre is a little altered in the seasonal-forcing case. These effects result in slightly lower densities of subducted water and the eastward shift of the MLD front.  相似文献   

Sources and depositional processes of tsunami deposits: Analysis using foraminiferal tests and hydrodynamic verification     

Jun‐Ichi Uchida  Osamu Fujiwara  Shiro Hasegawa  Takanobu Kamataki 《Island Arc》2010,19(3):427-442

Foraminiferal tests are commonly found in tsunami deposits and provide evidence of transport of sea floor sediments, sometimes from source areas more than 100 m deep and several kilometers away. These data contribute to estimates of the physical properties of tsunami waves, such as their amplitude and period. The tractive force of tsunami waves is inversely proportional to the water depth at sediment source areas, whereas the horizontal sediment transport distance by tsunami waves is proportional to the wave period and amplitude. We derived formulas for the amplitudes and periods of tsunami waves as functions of water depth at the sediment source area and sediment transport distance based on foraminiferal assemblages in tsunami deposits. We applied these formulas to derive wave amplitudes and periods from data on tsunami deposits in previous studies. For some examples, estimated wave parameters were reasonable matches for the actual tsunamis, although other cases had improbably large values. Such inconsistencies probably reflect: (i) local amplification of tsunami waves by submarine topography, such as submarine canyons; and (ii) errors in estimated water depth at the sediment source area and sediment transport distance, which mainly derive from insufficient identification of foraminiferal tests.  相似文献   

Centrifuge modeling of buried continuous pipelines subjected to normal faulting   总被引：1，自引：1，他引：0  

Majid Moradi  Mahdi Rojhani  Abbas Galandarzadeh  Shiro Takada 《地震工程与工程振动(英文版)》2013,12(1):155-164

Seismic ground faulting is the greatest hazard for continuous buried pipelines.Over the years,researchers have attempted to understand pipeline behavior mostly via numerical modeling such as the finite element method.The lack of well-documented field case histories of pipeline failure from seismic ground faulting and the cost and complicated facilities needed for full-scale experimental simulation mean that a centrifuge-based method to determine the behavior of pipelines subjected to faulting is best to verify numerical approaches.This paper presents results from three centrifuge tests designed to investigate continuous buried steel pipeline behavior subjected to normal faulting.The experimental setup and procedure are described and the recorded axial and bending strains induced in a pipeline are presented and compared to those obtained via analytical methods.The influence of factors such as faulting offset,burial depth and pipe diameter on the axial and bending strains of pipes and on ground soil failure and pipeline deformation patterns are also investigated.Finally,the tensile rupture of a pipeline due to normal faulting is investigated.  相似文献   

Improving strategies with constraints regarding non-Gaussian statistics in a three-dimensional variational assimilation method     

Norihisa?UsuiEmail author  Shiro?Ishizaki  Yosuke?Fujii  Masafumi?Kamachi 《Journal of Oceanography》2011,67(3):253-262

We assess validity of a Gaussian error assumption, the basic assumption in data assimilation theory, and propose two kinds of constraints regarding non-Gaussian statistics. In the mixed water region (MWR) off the east coast of Japan exhibiting complicated frontal structures, a probability density function (PDF) of subsurface temperature shows double peaks corresponding to the Kuroshio and Oyashio waters. The complicated frontal structures characterized by the temperature PDF sometimes cause large innovations, bringing about a non-Gaussianity of errors. It is also revealed that assimilated results with a standard three-dimensional variational (3DVAR) scheme have some issues in MWR, arising from the non-Gaussianity of errors. The Oyashio water sometimes becomes unrealistically cold. The double peaks seen in the observed temperature PDF are too smoothed. To improve the assimilated field in MWR, we introduce two kinds of constraints, J _c1 and J _c2, which model the observed temperature PDF. The constraint J _c1 prevents the unrealistically cold Oyashio water, and J _c2 intends to reproduce the double peaks. The assimilated fields are significantly improved by using these constraints. The constraint J _c1 effectively reduces the unrealistically cold Oyashio water. The double peaks in the observed temperature PDF are successfully reproduced by J _c2. In addition, not only subsurface temperature but also whole level temperature and salinity (T–S) fields are improved by adopting J _c1 and J _c2 to a multivariate 3DVAR scheme with vertical coupled T–S empirical orthogonal function modes.  相似文献   

Time-varying sources derived from EUV spectroheliograms of the quiet Sun     

Takara Nishikawa 《Solar physics》1986,105(2):339-354

Activity in the chromosphere-corona transition region of the quiet Sun is found both at network boundaries and in cell interiors using a time series of the EUV spectroheliograms obtained with the Harvard experiment on Skylab. We identify time-varying sources by subtracting the minimum count at each pixel in the time series from the counts at any time. Larger flux enhancements in emission lines occur only at the network boundary, though the cell interiors also have variable intensities. Time-varying sources in the cell interior appear often in the shape of streaks which seem to originate from sources at the network boundary, or as expanding network boundary sources. It is likely that the sources in the cell interior come from the transition sheaths of chromospheric inhomogenities. A multi-temperature analysis shows that two types of sources occur in the quiet Sun. One is due to heating of cool chromospheric inhomogenities like dark mottles. Sometimes cool matter is heated to coronal temperatures. The typical mass of the coronal material produced is 10¹¹-10¹²g. The other type seems to be due to draining of transition region material at the network boundary as the result of thermal instabilities. This quiet Sun activity is compatible with the time-varying sources at 6 cm wavelength.  相似文献   

High thallium content in Kuroko-type ore     

Satoshi Murao  Shiro Itoh 《Journal of Geochemical Exploration》1992,43(3)

Tl, Ga and Ge contents of Kuroko and other types of ore deposits were analysed semiquantitatively and quantitatively. The results show that Tl content is extremely high in Kuroko-type deposits compared to other types of mineralization. The T1 content is especially high in yellow ore and pyrite crystals; thus this element is considered to be incorporated in pyrite.  相似文献   

Changes in microbial community composition in the leaf litter of successional communities after volcanic eruptions of Mount Usu,northern Japan     

Michiru?OtakiEmail author  Fumiko?Takeuchi  Shiro?Tsuyuzaki 《山地科学学报》2016,13(9):1652-1662

Changes in the fungal and bacterial biomass and community structure in litter after the volcanic eruptions of Mount Usu, northern Japan were investigated using a chronosequence approach, which is widely used for analyzing vegetation succession. The vegetation changed from bare ground(10 years after the eruptions) with little plant cover and poor soil to monotonic grassland dominated by Polygonum sachalinense with undeveloped soil(33 years) and then to deciduous broad-leaved forest dominated by Populus maximowiczii with diverse species composition and well-developed soil(100 years). At three chronosequential sites, we evaluated the compositions of phospholipid fatty acids(PLFAs), carbon(C) and nitrogen(N) contents and the isotope ratios of C(δ13C) and N(δ15N) in the litter of two dominant species, Polygonum sachalinense and Populus maximowiczii. The C/N ratio, δ13C and δ15N in the litter of these two species were higher in the forest than that in the bare ground and grassland. The PLFAs gradually increased from the bare ground to the forest, showing that microbial biomass increased with the development of the soil and/or vegetation. The fungi-to-bacteria ratio of PLFA was constant at 5.3 ± 1.4 in all three sites, suggesting that fungi were predominant. A canonical correspondence analysis suggested that the PLFA composition was related tothe successional ages and the developing soil properties(P 0.05, ANOSIM). The chronosequential analysis effectively detected the successional changes in both microbial and plant communities.  相似文献