Large-Scale Turbulence Structures and Their Contributions to the Momentum Flux and Turbulence in the Near-Neutral Atmospheric Boundary Layer Observed from a 213-m Tall Meteorological Tower     

Mitsuaki Horiguchi  Taiichi Hayashi  Ahoro Adachi  Shigeru Onogi 《Boundary-Layer Meteorology》2012,144(2):179-198

Large-scale turbulence structures in the near-neutral atmospheric boundary layer (ABL) are investigated on the basis of observations made from the 213-m tall meteorological tower at Tsukuba, Japan. Vertical profiles of wind speed and turbulent fluxes in the ABL were obtained with sonic anemometer-thermometers at six levels of the tower. From the archived data, 31 near-neutral cases are selected for the analysis of turbulence structures. For the typical case, event detection by the integral wavelet transform with a large time scale (180 s) from the streamwise velocity component (u) at the highest level (200 m) reveals a descending high-speed structure with a time scale of approximately 100 s (a spatial scale of 1 km at the 200-m height). By applying the wavelet transform to the u velocity component at each level, the intermittent appearance of large-scale high-speed structures extending also in the vertical is detected. These structures usually make a large contribution to the downward momentum transfer and induce the enhancement of turbulent kinetic energy. This behaviour is like that of “active” turbulent motions. From the analysis of the two-point space–time correlation of wavelet coefficients for the u velocity component, the vertical extent and the downward influence of large-scale structures are examined. Large fluctuations in the large-scale range (wavelet variance at the selected time scale) at the 200-m level tend to induce the large correlation between the higher and lower levels.  相似文献   

Features of the orbital variability in the brightness of the WZ Sge type dwarf nova V1108 Her     

E. P. Pavlenko  T. Kato  O. I. Antonyuk  A. Imada  R. Ishioka  H. Maehara 《Astrophysics》2011,54(4):483-495

Results are presented from photometric studies of the dwarf nova V1108 Her conducted at the primary focus of the 2.6-m G. A. Shajn Telescope at the Crimean Astrophysical Observatory during June-July 2008, 4 years after the 2004 outburst. An orbital period of 0.05672(4) days is found for the system. An analysis of observations made earlier during the 2004 outburst reveals an orbital signal which indicates that V1108 Her is an eclipsing system. The mass ratio of the secondary component to the white dwarf is estimated to be q = 0.068, which makes it highly likely that the secondary component of this system is a brown dwarf. The orbital light curves indicate a complex structure for the accretion disk whose radius has reached a 2:1 resonance. An explanation is suggested for a quasi-periodic modulation in the brightness at 1/4 of the orbital period observed in V1108 Her and other WZ Sge systems.  相似文献   

Diffuse galactic FUV radiation and interstellar dust grains     

Shigeru Yoshioka 《Astrophysics and Space Science》1972,16(3):421-431

A re-analysis of the diffuse far UV radiation ( 1350–1480 Å) observed in the sky region ofl ^II180° and 0°b ^II40° is presented, as a revised version of a paper by Hayakawaet al. (1969). In comparison with the previous one, the value of the half optical depth of the Galazxy in our wavelength region is reduced, and the values of the albedo coefficient and the forward phase functiong are not well determined. If, however, we combine our results with the theoretical model of interstellar grains by Gilra, the value of is given by 0.13(5)0.18(5).  相似文献   

Hydrodynamic equations of differentially rotating stellar systems and the velocity ellipsoid     

Shoji Kato 《Astrophysics and Space Science》1968,2(1):37-47

Anisotropic hydrodynamic equations for differentially rotating collisionless stellar systems are derived. These equations can describe the evolution of the systems in a time span longer than their rotation periods.As a by-product of derivation of hydrodynamic equations, the well-known relation that the ratio of the principal axes of the velocity ellipse in a differentially rotating stellar disk is [B/(B-A)]^1/2 is re-found if the system is in a purely circular rotation, whereA andB are the Oort's constants. In addition, we find a systematic mean motion superposed on a purely circular differential rotation makes the directions of axes of the velocity ellipse deviate from the radial and the transverse direction. The observed deviation of directions of axes in our neighbourhood in the Galaxy can be explained if in the mean motion superposed on a purely circular differential rotatin the gas of stars near us is compressed in the radial direction or rarefied in the transverse directions, with irregularities of the order of 5 km/sec in amplitude of velocity and 1 kpc in size. These magnitudes of irregularities agree with those actually observed or with those anticipated from other theoretical considerations.  相似文献   

Possible Mechanism of Precursory Seismic Quiescence: Regional Stress Relaxation due to Preseismic Sliding   总被引：3，自引：0，他引：3  

N. Kato  M. Ohtake  T. Hirasawa 《Pure and Applied Geophysics》1997,150(2):249-267

—We propose a new model to physically explain the seismic quiescence precursory to a large interplate earthquake. A numerical simulation is performed to quantitatively examine possible stress changes prior to a great interplate earthquake in a subduction zone. In the present study, the frictional force following a laboratory-derived friction law, in which the friction coefficient is dependent on slip rate and slip history, is assumed to act on a dip-slip fault plane of infinite width in a uniform elastic half-space. The values of friction parameters are determined so that the result of numerical simulation may explain some properties of great interplate earthquakes in subduction zones, such as the recurrence interval and the seismic coupling coefficient. The result of simulation reveals that significant quasi-stable sliding occurs prior to a great earthquake and, accordingly, stresses are changed on and around the plate boundary. In a relatively wide area of the overriding continental plate, the compres sional horizontal-stress perpendicular to the trench axis is decreased for a few years before the occurrence of a great earthquake. This decrease in regional compressional stress may account for the appearance of seismic quiescence prior to a great interplate earthquake.  相似文献   

Multicomponent observation of crustal activity in the DPRI 800 m borehole close to the Nojima Fault   总被引：1，自引：0，他引：1  

Hiroshi Ishii  Atsushi Mukai  Kunio Fujimori  Shigeru Nakao  Shigeo Matsumoto  Yasuhiro Hirata 《Island Arc》2001,10(3-4):282-287

Abstract An 800 m borehole was drilled near the Nojima Fault, on which a strike–slip larger then 1 m occurred during the 1995 Hyogo-ken Nanbu earthquake ( M = 7.2). Crustal activity near the fault has been observed since May 1996 using a multicomponent instrument installed at the bottom of the borehole. Data of three components of strain, two components of tilt and temperature observed from May 1996 to December 1998 were analyzed. Long-term changes of strain and tilt show a north-east–south-west extension and southwards subsidence. As for the Earth tides and atmospheric effect, orientation of the principal axis of strain was mainly east-west and orientation of the maximum subsidence was mainly north-south. The observational data of strain had variations corresponding to a change in temperature at a depth of 800 m. The thermal expansion coefficient of the crust was calculated to be approximately 2.0 × 10⁻⁶/°K.  相似文献   

Steady mass-loss from supermassive stars     

Mariko Kato 《Astrophysics and Space Science》1986,119(1):57-59

Structures of Newtonian super-massive stars are calculated with the opacity for Comptor effectK ₀/(1 + T), whereK ₀=0.21(1 +X and =2.2×10^–9K^–1. The track of the Main-Sequence is turned right in the upper part of the HR diagram. Mass loss will occur in a Main-Sequence stage for a star with mass larger than a critical mass. The cause of mass loss and the expansion of the radius is continuum radiation pressure. The critical mass for mass loss is 1.02×10⁶ M for a Population I star, and 1.23×10⁵ M for Population III star. Mass loss rates expected in these stars are 3.3×10^–3 and 4.0×10^–3 M yr^–1, respectively.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Solubility of sulfur in some magmas at 1 atmosphere     

Takashi Katsura  Shigeru Nagashima 《Geochimica et cosmochimica acta》1974,38(4):517-531

In order to understand the distribution of sulfur in igneous rooks, we determined the solubility of sulfur in volcanic rock melts (tholeiite basalt, hawaiite and rhyodacite from Hawaii) at various gas compositions and at 1250° and 1300°C and 1 atm total pressure. The solubility of sulfur in the melt passes through a minimum with change in oxygen partial pressure, if other factors are held constant. For the basaltic liquid at 1200°C, most sulfur in the melt is as dissolved sulfide (S^?2) at oxygen partial pressures below 10^?8 atm and as dissolved sulfate at oxygen partial pressures above 10^?8 atm. Based on the present solubility data, 5 per cent is inferred for volcanic gas at 1 atm total pressure in equilibrium with subaerially extruded Hawaiian tholeiite basalt (Pele's hair with 180 ppm S) at 1200°C and 10^?8 atm P_O2.  相似文献   

Observations of the total lunar eclipse on March 24, 1978, at 3.4-mm wavelength     

Yasuo Fukui  Shigeru Hata  Takeshi Miyaji  Yoshihiro Chikada 《Icarus》1979,40(2):309-314

Observations of the total lunar eclipse were made at 3.4-mm wavelength (87.4 GHz) on March 24, 1978. Eclipsr cooling curves with the best S/N ratio among those published thus far were obtained for the three points (the mountain area near the crater of Hipparuchus, Sinus Medii, and Copernicus). Each of the curves can be decomposed into the three parts which apparently correspond to ingress, totality, and egress. The derived cooling rate and heating rate differ significantly at the three points.  相似文献   

V-2 Study on the system simulation for an O.W.C. type wave energy absorber     

Takeshi Kinoshita  Koichi Masuda  Shogo Miyajima  Wataru Kato 《Ocean Engineering》1985,12(6):580-581

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