Estimates of continental-scale soil wetness and comparison with the soil moisture data of Mintz and Serafini     

H. Matsuyama  K. Masuda 《Climate Dynamics》1997,13(10):681-689

 Soil wetness, in both its global distribution and the seasonal change, has been mainly estimated by the water balance approach using the bucket model which regards the soil wetness as soil moisture. The soil moisture data of Mintz and Serafini is one of the representatives examples, however, this method has problems since it does not incorporate the effects of flooding, snow accumulation on the ground, and so on. In this study, we use the Amazon and Volga river basin to carry out a case study to evaluate these problems. In the Amazon river basin, the annual range of the entire terrestrial water storage, about 400 mm, can be mainly explained by the rising and falling of the water level, and flooding around river channels, although soil moisture data of Mintz and Serafini is almost constant throughout the year. In the Volga river basin, snow accumulates on the ground producing 80 mm of water equivalent during winter, however the soil moisture data of Mintz and Serafini is almost saturated in winter. Received: 30 October 1996 / Accepted: 4 June 1997  相似文献   

Emergent radiation from the atmosphere bounded by the two halves of the Lambert surface with different albedos     

T. Takashima  K. Masuda 《Astrophysics and Space Science》1991,183(2):225-236

For the evaluation of the effect of the nonuniform surface albedo to the emergent radiation from the atmosphere, the emergent radiation from the atmosphere bounded by the two-halves of the Lambert surface with different albedos is computed. The principal plane is assumed to be perpendicular to the boundary of surfaces. The atmosphere is assumed to be homogeneous, which is composed of aerosol, molecules, and absorbent gases. Their optical thicknesses are 0.25, 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 approximated by the contributions due to the multiple scattering in the atmosphere, directly attenuated radiation, and radiation due to single scattering in the atmosphere which is reflected by the Lambert surface (up to 4 interactive radiative modes between atmosphere and surface). For quantitative analysis, results are compared with those of the atmosphere-uniform surface model, where the multiple scattering is considered. The numerical simulation exhibits the extraordinary effect near the surface boundary of different albedos. The effect decreases exponentially with the distance from the boundary. It is a function of the observational position, difference of surface albedos, optical thickness and aerosol type.The upward radiance would simply be evaluated using the present scattering approximation method if the atmosphere is in clear condition. Whereas in hazy condition, the effect of multiple scattering in the atmosphere should be considered more precisely, since the upward radiance exhibit a strong dependence on observational nadir angles due to multiple scattering in the atmosphere. Furthermore, it depends on the optical characteristics of aerosols.  相似文献   

Rare-earths in Icelandic neovolcanic rocks     

Toshinari Shimokawa  Akimasa Masuda 《Contributions to Mineralogy and Petrology》1972,37(1):39-46

Seven volcanic rocks from neovolcanic zone of Iceland were analysed for rare-earths (RE). The bulk partition coefficients are estimated from combination of the studied samples. In contrast with the mid-ocean ridge basalts which show the solid-type RE patterns, four of five arbitrarily chosen Icelandic basalts appear to have liquid-type RE patterns. The occurrence of relatively pristine lava with relative unfractionated RE abundances to chondrite is also considered to be associated with the peculiar tectonics of Iceland.  相似文献   

Velocity Measurements and Crack Density Determination During Wet Triaxial Experiments on Oshima and Toki Granites     

A. Schubnel  O. Nishizawa  K. Masuda  X. J. Lei  Z. Xue  Y. Guégen 《Pure and Applied Geophysics》2003,160(5-6):869-887

— A set of experiments on four samples of Oshima Granite at 15, 40 and 60 MPa confining pressure have been performed in order to investigate the damage behavior of granite submitted to deviatoric stress. In addition an experiment on one sample of Toki Granite at 40 MPa confining pressure was performed, in order to compare and elucidate the structural effects. Using acoustic emission data, strain measurements and elastic wave velocities allow to define consistently a damage domain in the stress space. In this domain, microcracking develops. The microcracking process is, in a first stage, homogeneous and, close to failure, localized. Elastic wave velocities decrease in the damage domain and elastic anisotropy develops. Using Kachanov's model (1993), elastic wave velocities have been inverted to derive the full second-order crack density tensor and characterize the fluid saturation state from the fourth-order crack density tensor. Crack density is strongly anisotropic and the total crack density close to failure slightly above one. The results indicate that the rock is saturated in agreement with the experimental conditions. The model is thus shown to be very appropriate to infer from elastic wave velocities a complete quantitative characterization of the damaged rock.  相似文献   

Simultaneous Observation of Solar Neutrons from the International Space Station and High Mountain Observatories in Association with a Flare on July 8, 2014     

Y. Muraki  D. Lopez  K. Koga  F. Kakimoto  T. Goka  L. X. González  S. Masuda  Y. Matsubara  H. Matsumoto  P. Miranda  O. Okudaira  T. Obara  J. Salinas  T. Sako  S. Shibata  R. Ticona  Y. Tsunesada  J. F. Valdés-Galicia  K. Watanabe  T. Yamamoto 《Solar physics》2016,291(4):1241-1265

  相似文献   

Group velocity and energy transport by Rossby waves     

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   

A proof and applications of the expansion theorem for the Rossby normal modes in a closed rectangular basin     

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   

A laboratory study of directional spectra with maximum likelihood method─I Developing wind wave     

Zhao Dongliang  Masuda Akira  Wen Shengchang  Guan Changlong 《海洋学报(英文版)》1999,(1)

INTRODUCTIONDirectionalspectraofwind-generatedwavesareveryimportanttotheresearchrelatedto1.InstituteofPhysicalOceanography,OceanUniversityofQingdao,Qingdao266003,China2.ResearchinstituteforAppliedMechanics,KyUshuUniversity,Kasuga816,Japanwindwaves.Theyfindapplicationinfieldsasdiverseasbasicair-seainteraction,practicalwaveforecasting,satellitesurveillanceandengineeringdesignofmarinestructuresandvehicles.Sincethepioneeringworkofthestereowaveobservationproject(Coteetal.11960),alotofeff…  相似文献   

Bathymetric influences of the Emperor Seamounts upon the subarctic gyre of the North Pacific: Examining boundary current dynamics along the eastern side of the mountain ridge with an idealized numerical model     

Taku Wagawa  Yutaka Yoshikawa  Akira Masuda 《Journal of Oceanography》2010,66(2):259-271

The possible influences of the Emperor Seamounts (ESs) upon the subarctic gyre of the North Pacific (NPSAG) were investigated by a series of numerical experiments. In the experiments, a two-layer ocean with a meridional mountain ridge was forced by seasonally varying wind stress. We focused on how the return ratio, the ratio of the boundary transport along the eastern side of the ridge to the interior Sverdrup transport, changes with ridge height, width and density stratification. It was found that the return ratio can be large if the ridge width is greater than the width of the viscous boundary layer. In this case, the bottom pressure torque determines the return ratio; the return ratio is almost proportional to the ridge height when the ridge height is small and some contours of planetary potential vorticity pass over the ridge. However, the return ratio is independent of the ridge height and decreases with the stratification when the ridge height is large and all the contours of planetary potential vorticity are closed. These dependences of the return ratio were understood in terms of barotropic and baroclinic components of the bottom pressure torque. Implications for the bathymetric influences of ESs on the actual NPSAG are also discussed.  相似文献   

Interannual variability of North Pacific eastern subtropical mode water formation in the 1990s derived from a 4-dimensional variational ocean data assimilation experiment     

T. Toyoda  T. Awaji  S. Masuda  N. Sugiura  H. Igarashi  T. Mochizuki  Y. Ishikawa 《Dynamics of Atmospheres and Oceans》2011,51(1-2):1-25

The interannual variability of eastern subtropical mode water (ESTMW) formation in the North Pacific is examined using a new ocean dataset constructed by a 4-dimensional variational data assimilation experiment covering the decade of the 1990s. The volume of newly formed ESTMW varies due to interannual variability in the following three physical processes taking place in the surface layer: (1) convergence in the transport of surface saline water induced by Ekman flow in the vicinity of the formation region, (2) thermal stratification in the preconditioning phase in association with the insolation anomaly induced largely by low-level cloud coverage, and (3) wintertime surface cooling in the eastern subtropics. We find that, in addition to the surface forcing, the properties of both the ESTMW and the upper mixed-layer water are broadly controlled by the volume of the new ESTMW component, and that the variations in the upper mixed-layer water affect the properties of ESTMW formed in the following winter. Due to the combined effect of these processes, the ESTMW subducts down to subsurface layers with a wide range of σ_θ values lying between 24.8 and 25.4 and with significant interannual variation in water mass formation.  相似文献