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61.
Wind-wave spectra measured in a wind-flume are analyzed according to the hypothesis of local equilibrium. The gross relation between the wave height and the frequency is reexamined to yield the basic validity of the 3/2-power law of Toba orE~? in the range of 0.4≦?≦1, where? is the wave-wind parameter defined by?=ω p u */g; ω p denotes the peak frequency of the wind-wave spectra,u * the friction velocity andg the gravitational acceleration. Noticeable deviation is found, however, for?<0.4 or?>1. In particular, the data for large? suggest the existence of an upper limit of the wave nonlinearityE at about 5×10?2, whereE=Eω p 4 /g2 withE the total power of the wind wave spectrum. Then, the spectral form is investigated in detail. As? decreases, the normalized spectrum becomes more gradual as a whole, but its forward (low frequency) part tends to show a steeper profile. In the high frequency region ( \(\tilde \omega \) >2.6), the spectrum is found to have a functional form likeu * 2 ω ?3, which differs from the usualω-dependence asω ?5 orω ?4. It suggests weak dependence of the high-frequency spectra on the gravitational accelerationg and on the peak frequencyω p ; spectral density at high frequencies may be saturated, so that its magnitude may be dominated by the frequencyω, the friction velocityu *, the surface tension and the viscosity. 相似文献
62.
For the evaluation of the effect of the non-uniform surface albedo on the emergent radiation from the atmosphere, the emergent radiation from the atmosphere bounded by the two half Lambert surfaces composed of different albedo is computed. This paper is the improved version of the previous paper (Takashima and Masuda, 1991). The atmosphere is assumed to be homogeneous, which is composed of aerosol, molecules, and absorbent gases. Their optical thicknesses are (1) 0.25, 0.23, and 0.02, and (2) 0.75, 0.23, and 0.02, respectively. The model aerosol is of the oceanic and water soluble types.In the computational procedure, the emergent radiation is calculated approximately by the contributions due to the multiple scattering in the atmosphere, and due to the diffusely or directly transmitted radiation through the atmosphere which is reflected by the surfaces once (4 interactive radiative modes between atmosphere and surface). Furthermore, to perform the hemispherical integration processing the radiative interaction, the transmission function based on the single scattering in the atmosphere is introduced and then the transmission function is averaged over the hemisphere with weighting function. The numerical simulation exhibits the extraordinary effect near the two half surface boundary of different albedoes. The effect decreases exponentially with the distance from the boundary. The effect depends on the atmospheric aerosol type, optical thickness, and surface albedo. The present version enables us to quantitatively discuss the radiative transfer trend near the boundary of two half surfaces. The upward radiance would simply be evaluated using the present scattering approximation method if the surface albedo is less than 0.3. The present method is thought of as a first step extending the one-dimensional radiative transfer model to two-dimensional using the doubling-adding method. 相似文献
63.
Akira Masuda 《Journal of Oceanography》1978,34(1):1-7
A variational method gives a proof that, for normal modes of Rossby waves in the ocean on a-plane with depth variable in the meridional direction, the time average of the energy flux defined as the product of the pressure and the fluid-particle velocity agrees with the time average of the energy density multiplied by the group velocity. This conclusion holds in considerably general situations and sheds light on the controversial problem of the energy transport by Rossby waves. Moreover, the variational method gives a remarkable relation between the group velocity and the phase velocity. In particular this relation shows that the absolute value of the group velocity never exceeds that of the phase velocity. 相似文献
64.
J. Sato Y. Matsumoto K. Yoshimura S. Kubo J. Kotoku S. Masuda M. Sawa K. Suga M. Yoshimori T. Kosugi T. Watanabe 《Solar physics》2006,236(2):351-368
The flare catalogue of the Yohkoh mission is compiled and linked to this article as an electronic supplement. For showing flare characteristics over wide energy
range concisely, we provide the images of Hard X-ray Telescope (HXT) and the Soft X-ray Telescope (SXT), and the spectra of
Hard X-ray Spectrometer (HXS) and Gamma-Ray Spectrometer (GRS) with the Wide Band Spectrometer (WBS) time profiles. The energy
versus pulse height (PH) data channels in HXS and GRS are re-calibrated by using the data of the whole mission period. Secular
gain changes are recognized in HXS, and the characteristics of power-law flare spectra simultaneously observed by HXT and
HXS confirms the trend. The GRS gains are different for the flare observations during the previous maximum and for the current
maximum. The total of 33 γ -ray events are observed, and for 12 of them γ-ray flare spectra are obtained.
Electronic supplementary material to this article is available at and is accessible for authorized users. 相似文献
65.
Ayumi Asai Takaaki Yokoyama Masumi Shimojo Satoshi Masuda Kazunari Shibata 《Journal of Astrophysics and Astronomy》2006,27(2-3):167-173
We report a detailed examination about the relationship between the evolution of the Hα flare ribbons and the released magnetic
energy during the April 10 2001 flare. In the Hα images, several bright kernels are observed in the flare ribbons. We identified
the conjugated foot-points, by analyzing the lightcurves at each Hα kernels, and showed their connectivities during the flare.
Then, based on the magnetic reconnection model, we calculated quantitatively the released energy by using the photospheric
magnetic field strengths and separation speeds of the Hα flare ribbons. Finally, we examined the downward motions which are
observed at the Hα kernels. We found that the stronger the red-asymmetry tends to be associated with the brighter the Hα kernel. 相似文献
66.
Numerical 3D simulations of the development of spiral inclusion trails in porphyroblasts were conducted in order to test the proposals that (a) 3D spiral geometry differs between the rotation and nonrotation end‐member models of spiral formation proposed in the literature, and (b) 3D spiral geometry can be used as a criterion to distinguish between the two end‐member models in rocks. Four principal differences are identified between the two sets of simulations: smoothness of spiral curvature; spacing of foliation planes; alignment of individual foliation planes either side of the sphere representing the porphyroblast; and spiral asymmetry with respect to matrix shear sense. Of these differences, only spiral asymmetry and possibly the alignment of individual foliation planes are diagnostic criteria for distinguishing between the end‐member models. In the absence of a readily applied test to distinguish the end‐member models, interpretation of spiral inclusion trails is problematic. It is necessary to determine complementary evidence to distinguish porphyroblast rotation or nonrotation during spiral formation. 相似文献
67.
Tomoyuki Sato Keisuke Taniguchi Tomohiro Takagawa Fujio Masuda 《Geo-Marine Letters》2011,31(2):101-108
Flume experiments aimed to produce flaser bedding were conducted using fine sand and clay in a circular flume. The formation
process of mud drapes during the slack-water stage was revealed in detail. When the tidal current declines, a uniform mobile
mud layer initially settles from suspension and drapes the entire rippled sand bed (type A mud). When the remaining flow velocity
is very low, a more fluid mud begins to settle out (type B mud) that preferentially fills the ripple troughs, the ripples
and mud together forming a flat surface. At slack tide, the two-phase mud drape is temporarily stationary. After the onset
of the reversed flow phase, most of the type B mud is resuspended, while the type A mud is eroded from the crests, leaving
behind a remnant mud drape (flaser) in the troughs that is subsequently buried by migrating ripples. Type B mud generally
contains variable amounts of sand derived from eroded ripple crests, but does not show any visible internal sedimentary structures.
Type A mud represents the ‘mud drapes’ commonly described in the literature, the temporary existence of type B mud having
gone unnoticed because of its low preservation potential. When present, it can be recognized by its sand content and the occurrence
of flame structures in ripple troughs. Tidal deposits reflecting the existence and depositional characteristics of both type
A and type B mud are found in, for example, the macrotidal Oligocene Ashiya Group, Japan. 相似文献
68.
A new method for simulation of atmospheric effect on the emergent radiation over non-uniform terrain
For a precise atmospheric correction over the non-uniform terrain in satellite imageries, a numerical method for evaluating the upwelling radiation at the top of the atmosphere bounded by the non-uniform surface is developed as an extended doubling-adding method. The present method enable us to treat quantitatively the case of hazy atmosphere and (or) large albedo of the surface. 相似文献
69.
This study describes surface cyclone activity associated with the interannual variability in summer precipitation in northern Eurasia and how that activity may be connected to other climate signals. An east–west seesaw oscillation of precipitation across Siberia is the primary mode of interannual variability in the summer hydrological cycle over northern Eurasia. This variation occurs at sub-decadal timescales of about 6–8 years. The spatial characteristics of cyclone frequency and cyclone tracks at the two poles in variability [eastern Siberia (ES)-wet–western Siberia (WS)-dry and WS-wet–ES-dry] were examined, and temporal variability in regional cyclone frequency was compared to basin-scale precipitation variability. The analysis period was from 1973 to 2002, when the precipitation variability signal was predominant.Cyclone behavior suggested that the regions of enhanced (reduced) cyclone activity coincided with regions of increased (decreased) precipitation in each phase of the oscillation. Such behavior reflects the zonal displacement of the track of frequent storm activity that accompanies the changes in precipitation. Comparisons of the temporal characteristics confirmed the importance of regional cyclone frequency on precipitation variability in both eastern and western Siberia. Low-frequency changes in regional cyclone activity may produce the precipitation oscillation. We used various climate signals to explore connections between regional precipitation and cyclone activity in Siberia. Results suggest that the North Atlantic Oscillation (NAO) from the preceding winter is significantly and negatively correlated with summer surface cyclone frequency and precipitation over western Siberia. Enhanced (reduced) summer cyclone activity and precipitation in western Siberia follows low- (high-) winter NAO. However, the physical mechanisms linking summer cyclone activity and precipitation over western Siberia with the preceding climate conditions associated with the winter NAO remain unclear. 相似文献
70.
Akira Masuda 《Journal of Oceanography》1987,43(4):237-243
An expansion theorem is derived for Rossby normal modes in a closed rectangular basin and the set of Rossby normal modes is proved to be complete. This theorem provides a general linear solution to the initial value problem as well as to the response problem. In particular, the Green's function is obtained for the instantaneous localized torque anywhere in the basin. Weakly nonlinear versions are solved also by the combination of the general linear solution with the asymptotic expansion in terms of small amplitude. Further, an application is suggested to the spectral method of numerical simulation based on Rossby normal modes relevant to the more nonlinear evolution equation on a-plane, instead ofsin functions or Chebyshev polynomials, which have been employed conventionally for this purpose. 相似文献