Organizations and the interior characteristics of winter monsoon clouds by dual-polarization Doppler radar observation in Hokuriku, Japan     

Yoshio Asuma  Katsuhiro Kikuchi  Hiroshi Uyeda 《Atmospheric Research》1997,43(4):297-314

To understand the characteristics of winter monsoon clouds, dual-polarization Doppler radar observations were carried out at Mihama, Hokuriku, Japan. A series of organized disturbances associated with the passage of a cyclonic circulation was analyzed. The following scenario was proposed. Environmental circumstances, for example, temperature and wind profiles, surface heat and moisture fluxes, etc., determine the organizational style of mesoscale convections. This organization regulates the convection interior flow pattern including the location and intensity of updrafts. Subsequently, it influences interior microphysical properties, for example, the types of precipitation particles, their growth and distributions, their electrification, etc. In this paper, an observational example following this scenario is presented.  相似文献   

High Ash Content in Net-Plankton Samples from Shallow Coastal Water: Possible Source of Error in Dry Weight Measurement of Zooplankton Biomass   总被引：2，自引：0，他引：2  

Norio Nagao  Tatsuki Toda  Kazutaka Takahashi  Koji Hamasaki  Tomohiko Kikuchi  Satoru Taguchi 《Journal of Oceanography》2001,57(1):105-107

Annual examination of net-plankton biomass in dry weight, ash-free dry weight, organic carbon, and nitrogen weight at the Manazuru harbor, central Japan revealed that net-plankton samples from shallow coastal water contained considerable amount of ash (53±13% of dry weight) which would be caused by contamination of inorganic materials from re-suspendion of sediments, terrestrial runoff and chain-forming diatoms. Therefore, in coastal water, dry weight is inadequate fro determination of zooplankton biomass in volving the possibility of over-estimation. Practical estimation of net-plankton biomass in shallow coastal waters, ash-free dry weight, organic carbon, and/or nitrogen are more adequate.  相似文献   

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions   总被引：2，自引：0，他引：2  

G. Chisham  M. Lester  S. E. Milan  M. P. Freeman  W. A. Bristow  A. Grocott  K. A. McWilliams  J. M. Ruohoniemi  T. K. Yeoman  P. L. Dyson  R. A. Greenwald  T. Kikuchi  M. Pinnock  J. P. S. Rash  N. Sato  G. J. Sofko  J.-P. Villain  A. D. M. Walker 《Surveys in Geophysics》2007,28(1):33-109

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Mineralogical and Geochemical Characteristics of the Utanobori Gold Deposit in Northern Hokkaido,Japan     

Thomas T. Sorulen  Ryohei Takahashi  So Tanaka  Kana Suzuki  Akira Imai  Yasushi Watanabe  Shingo Kikuchi 《Resource Geology》2019,69(4):402-429

The Utanobori gold deposit is a low‐sulfidation, epithermal vein‐type deposit located in northern Hokkaido, Japan. The deposit is hosted by conglomerate, sandstone, and tuff of the Middle to Late Miocene Esashi Formation. These rocks were hydrothermally altered. Silica sinters and quartz‐adularia veins are common in the deposit. The quartz‐adularia veins either contain a ginguro band, which corresponds to the main gold‐bearing vein (Type 1 Veins), or do not contain a ginguro band but contain minor adularia (Type 2 Veins). Type 1 Veins are divided into three stages with 12–14 substages. Ore minerals identified include electrum, naumannite, chlorargyrite, bromargyrite, an unidentified Fe‐Sb mineral, and an Fe‐(Sb)‐As mineral. These ore minerals formed in the main mineralization stages I (bands I‐b and I‐d) and II (band II‐a). Scanning electron microscopy with cathodoluminescence images show that cathodoluminescence‐dark microcrystalline quartz exhibiting colloform (ghost‐sphere) texture is closely associated with ore minerals in the Type 1 Vein and Type 2 Vein, and the Al and K contents of such quartz are commonly >1000 ppm. This indicates that the ore minerals were crystallized from alkaline, silica‐saturated fluids at temperatures <200°C, which initially deposited amorphous silica that was recrystallized to microcrystalline quartz. The average Au content of electrum is 52.5 at% Au (n = 10), 65.7 at% Au (n = 20), and 55.5 at% Au (n = 5) in bands I‐b, I‐d, and II‐a, respectively, of Type 1 Veins. The δ³⁴S_CDT values of two fine‐grained disseminated pyrites in the altered conglomerate and bedded tuff in the argillic altered zone are ?4.3 and ?4.2‰. Ar‐Ar dating on adularia yielded 13.6 ± 0.06 Ma, 13.6 ± 0.07 Ma, and 13.6 ± 0.06 Ma for the stages I, II, and III of the Type 1 Vein, respectively. K‐Ar ages determined on adularia in the silica sinter and on whole‐rock of glassy rhyolite of the Esashi Formation are 15.0 ± 0.4 Ma and 14.6 ± 0.4 Ma, respectively. These radiometric ages indicate that silica sinter associated with the rhyolitic volcanic rocks formed prior to the main gold mineralization.  相似文献   

Estimation of the apertures of water-saturated fractures by nuclear magnetic resonance well logging   总被引：1，自引：0，他引：1  

Yoshito Nakashima  Tsuneo Kikuchi 《Geophysical Prospecting》2007,55(2):235-254

Fracture aperture is an important transport property in subsurface hydrology because it influences well productivity and the volume of the water resource. Nuclear magnetic resonance (NMR) well logging measures the hydrogen‐bearing fluid molecules in porous or fractured strata, and the NMR signal intensity increases with the amount of fluid in the sensed region of the NMR sonde. Fluid confined in a large fracture of >>0.2 mm in aperture has T2 (i.e. spin‐spin relaxation time) values as long as those of the bulk fluid. The bulk‐fluid porosity (i.e. porosity calculated using this long T2 component in a T2 histogram data) increases linearly with aperture. Therefore, NMR logging enables quantitative estimation of fracture apertures of >>0.2 mm using the bulk‐fluid porosity data if the calibration of the NMR sonde is performed adequately. We applied NMR logging to a borehole in a Holocene andesite lava at Sumikawa, Japan, to estimate the aperture of open fractures within the lava. A test well of 100 m depth and 20 cm diameter, filled with bentonite drilling mud, was scanned with an NMR sonde to obtain a profile of the porosity and the T2 histogram of the andesite. The bulk‐fluid porosity was calculated from the T2 histogram data, as the porosity at which the T2 value is larger than or equal to a threshold T2 of bulk bentonite mud. The bulk‐fluid porosity of a specific inclined fracture responsible for the total loss of circulation at 61.2 m depth during drilling was calculated assuming a threshold or T2 cut‐off of 33 ms, and again for a cut‐off of 100 ms. Calibration of the NMR sensor in a laboratory and measurement of the fracture dip angle by electrical microimaging logging enabled us to estimate the fracture aperture as 1.7 cm, assuming a T2 cut‐off of 33 ms, or 1.6 cm for a T2 cut‐off of 100 ms. The method of aperture determination described in this study is independent of fluid species and lithology, and is applicable to various hydrogen‐bearing borehole fluids (clean water, mud and oil) and geological settings.  相似文献   

Vertical heat transfer based on direct microstructure measurements in the ice-free Pacific-side Arctic Ocean: the role and impact of the Pacific water intrusion     

Yusuke Kawaguchi  Takashi Kikuchi  Ryuichiro Inoue 《Journal of Oceanography》2014,70(4):343-353

This study quantifies diapycnal mixing and vertical heat transfer in the Pacific side of the Arctic Ocean, where sea-ice cover has disappeared between July and September in the last few decades. We conducted microstructure measurements in the open water region around the Canada Basin from late summer to fall in 2009 and 2010 using R/V Mirai. In the study domain, the dissipation rate of turbulent kinetic energy, ε, is typically as low level as O(10^?10) W kg^?1, resulting in vertical heat diffusivity of O(10^?7) m² s^?1, which is close to the molecular diffusivity of heat, suggesting comparatively little predominance of mechanical turbulent mixing. An exception is the case at the Barrow Canyon, where the strong baroclinic throughflow generates substantial vertical mixing, producing ε > O(10^?7) W kg^?1, because of the shear flow instability. Meanwhile, in the confluence region, where the warm/salty Pacific water and the cold/fresh Arctic basin water encounter, the micro-temperature profiles revealed a localized enhancement in vertical diffusivity of heat, reaching O(10^?5) m² s^?1 or greater. In this region, an intrusion of warm Pacific water creates a horizontally interleaved structure, where the double-diffusive mixing facilitates vertical heat transfer between the intruding Pacific water and the surrounding basin waters.  相似文献   

An introduction to combined Fourier–wavelet transform and its application to convectively coupled equatorial waves     

Kazuyoshi Kikuchi 《Climate Dynamics》2014,43(5-6):1339-1356

Convectively coupled equatorial waves (CCEWs) are major sources of tropical day-to-day variability. The majority of CCEWs-related studies for the past decade or so have based their analyses, in one form or another, on the Fourier-based space–time spectral analysis method developed by Wheeler and Kiladis (WK). Like other atmospheric and oceanic phenomena, however, CCEWs exhibit pronounced nonstationarity, which the conventional Fourier-based method has difficulty elucidating. The purpose of this study is to introduce an analysis method that is able to describe the time-varying spectral features of CCEWs. The method is based on a transform, referred to as the combined Fourier–wavelet transform (CFWT), defined as a combination of the Fourier transform in space (longitude) and wavelet transform in time, providing an instantaneous space–time spectrum at any given time. The elaboration made on how to display the CFWT spectrum in a manner analogous to the conventional method (i.e., as a function of zonal wavenumber and frequency) and how to estimate the background noise spectrum renders the method more practically feasible. As a practical example, this study analyzes 3-hourly cloud archive user service (CLAUS) cloudiness data for 23 years. The CFWT and WK methods exhibit a remarkable level of agreement in the distributions of climatological-mean space–time spectra over a wide range of space–time scales ranging in time from several hours to several tens of days, indicating the instantaneous CFWT spectrum provides a reasonable snapshot. The usefulness of the capability to localize space–time spectra in time is demonstrated through examinations of the annual cycle, interannual variability, and a case study.  相似文献   

Predominant hosting lead(II) in ternary mixtures of heavy metal ions by a novel of diethylaminomethyl-calix[4]resorcinarene     

N. N. M. Yusof  Y. Kikuchi  T. Kobayashi 《International Journal of Environmental Science and Technology》2014,11(4):1063-1072

Heavy metal ions from single and ternary systems of Pb(II), Cu(II), and Ni(II) adsorbed by calix[4]resorcinarenes in water–chloroform extraction were studied. Comparison was made of calix[4]resorcinarenes, 2,8,14,20-tetraundecyl calix[4]resorcinarene-4,6,10,12,16,18,22,24-octol, and diethylaminomethyl-calix[4]resorcinarene, 5,11,17,23-tetra(diethylaminomethyl)-2,8,14,20- tetraundecylcalix[4]resorcinarene-4,6,10,12,16,18,22,24-octol, for predominant extraction of their ions from the ternary mixture of aqueous solution at different pH in a water layer. The hosting of Pb(II) by the diethylaminomethyl-calix[4]resorcinarene occurred efficiently at pH 6–7. The hosting of Pb(II), Cu(II), and Ni(II) ions for the ternary aqueous mixture was applied to the Langmuir isotherm. Adsorption was studied using nuclear magnetic resonance spectroscopy in a water–deuterium chloroform extraction system. Results showed that as the heavy metal ions were included into the host cavity, the observation of shifted peaks of water molecules from downfield to higher field was visible in the nuclear magnetic resonance spectra, meaning that water molecules were included with heavy metal ion into the host cavity. The spectra also showed that the diethylamino group expressed formation of the coordination complex between the diethylaminomethyl-calix[4]resorcinarene and Pb(II) for the purpose of predominant hosting of Pb(II).  相似文献